Trop. Anita. Hlth Prod. (1992) 24, 242-250
PLASMA PROGESTERONE CONCENTRATIONS DURING PREGNANCY AND PSEUDOPREGNANCY AND ONSET OF OVARIAN ACTIVITY P O S T P A R T U M IN INDIGENOUS GOATS IN ZIMBABWE C. A. LLEWELYN1'3, J. S. OGAA 2 and M. J. OBWOLO 2 IDepartment of Animal Science and 2Faculty of Veterinary Science, University of Zimbabwe, Mount Pleasant MP 167, Harare, Zimbabwe SUMMARY
Eight pregnant does were housed individually andfed a hay and concentrate diet throughout pregnancy and lactation. The mean gestation period was 146.7 + 3.0 days, with a twinning rate of 75 per cent. Mean body condition scores improved from 2.4 + 0.2 to 2.8 + 0.2 over the first 80 days of gestation and were maintained at 2.8 uhtil 45 days before kidding. From then until kidding, mean scores fell to 2.2 +_ 0.2. Plasma progesterone concentrations during pregnancy rose significantly from 3.91 + 0"51 ng/ml on day 40 to 5.96 ++_0.51 ng/ml on day 60 (P < 0.05) and remained high until 5 days before kidding. Three pseudopregnant does had similar progesterone profiles to pregnant does over the first 80 days, but the rise around day 35 to 40 was not significant and progesterone concentrations returned gradually to basal levels after day 100. The same 8 does, together with an additional 4 does which had been brought inside 60 to 70 days before kidding, were used to study onset of ovarian activity post partum. The twinning percentage was 83 per cent. Mean body condition score at parturition was 2"2 +_ 0"1. By day 35 post partum, mean condition scores hadfallen to 1.9 + 0.1, andmean weights from 36.9 + 1.gkg at kidding to 32.1 + 2.0kg. Ovarian cyclicity was resumed just before mean scores and weights started to improve. The mean intervalfrom kidding to onset of oestrous cycles was 97.3 + 9.5 days. This coincided with mean time to weaning which was 99.5 + 5.5 days. It is suggested that suckling and body condition regulate the length of post-partum anoestrus in this species. Season may also play a regulatory role, since does kidding in April t o June (n = 6) were anoestrus for 82"7 + 15"0 days compared to 112 + 7.3 days for does kidding in October to February (n = 6), although the difference was not significant. INTRODUCTION
There are approximately 1.8 million goats in Zimbabwe which are kept by subsistence farmers in the communal areas. Despite the belief that these goats are prolific breeders, productivity is generally low. Some of the reasons for this are high kid mortality rates and prolonged kidding intervals (Hale, 1986). In one study, a mean 9 value of 370 days was recorded and plasma progesterone profiles indicated that this was due to prolonged post-partum anoestrus (Ndlovu and Llewelyn, unpub, data), with most does remaining acyclical for over 150 days. It was thought that nutritional constraints were responsible for delaying the onset of post-partum activity in these goats, resulting in prolonged kidding intervals. The present study was designed to investigate progesterone profiles during pregnancy and to investigate onset of ovarian 3Present address: c[o Croyland House,Dry Drayton, Cambridge, CB3 8BU. 242
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TABLE I
Ingredients of the concentrate supplementfed to goats
Constituent
% of diet
Maize meal, ground Cotton seed hulls, ether extracted High protein concentrate, 65% urea Limestone flour Sodium chloride Trace element mix ~ Vitamin A Vitamin D
59.5 30.0
Energy content Crude protein
9.9 0.5 0,05 0.01 300 I.U./kg 300 I.U./kg 10 MJ/kg 13%
t To give a final concentrationof 3mg iron, 3mg iodine, 2.5 mg zinc, 0"75mg manganeseand 0.015mg cobalt per kg feed. activity in a group of goats receiving concentrate supplementation during pregnancy and lactation. MATERIALS AND METHODS
Eleven does from the University goat herd were housed in single pens and fed a diet of reid hay ad libitum supplemented with a ration based on maize meal and cotton seed hulls (Table I). Eight does were studied throughout pregnancy and 3 throughout a pseudopregnancy. To increase the numbers of does available for studying the interval from kidding to onset of ovarian activity from 8 to 12, another 4 pregnant does of comparable body condition were fed concentrate supplement for the last 60 to 70 days of pregnancy. All does received 0.25 kg/day of the concentrate ration, which was increased after parturition to 0-5 kg and to 1 kg/day for body condition scores of ~ 1.5. The goats were weighed weekly and scored 3 times a week to assess body condition using the method of Honhold et ak 0989). Mean interval from parturition to weaning was 99-5 _ 5.5 days (range 69 to 114). Goats were bled 3 times a week throughout the study. Blood was collected into tubes containing EDTA as anti-coagulant and kept on ice before centrifugation at 2,500g for 30minutes. Plasma was stored at -20~ to await radioimmunoassay (RIA). Progesterone concentrations were measured in 50/A plasma by a direct doubleantibody RIA according to the method of Corrie et aL (1981) with 2.5 pg of 125iodinated progesterone-lla-glucuronide-tyramine (Amersham International) as tracer and 500 ng/tube of danazol (Winthrop Sterling) to displace progesterone bound to plasma proteins. The first antiserum (R104/10) was raised in a rabbit against progesterone1la-hemisuc.~inate conjugated to bovine serum albumin and used at a titre of 1/4000. Cross reactions were as follows: ~lla-hydroxyprogesterone 15-9%, corticosterone 4.6%, deoxycorfisone 3.1%, 5a-pregnanedione 1-6%, l l-dehydrocorticosterone 1.2%, 17a-hydroxyprogesterone 0.6%, pregnenolone and oestrone < 0-1%. Cortisol, cortisone, androstenedione and testosterone were < 0-01% and oestradiol and oestriol < 0.001 per cent. The second antiserum was donkey anti-rabbit serum used with normal rabbit serum as carrier. The minimal detectable dose was 0.4 ng/ml and the intra-assay coefficient of variation was 14-1% and 10.7% for medium (2-4 ng/ml) and high (4"8 ng/ml) quality control pools respectively.
LLEWELYN, O G A A A N D O B W O L O
244 Body scocP
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FIG. 1. Changesin plasmaprogesteroneconcentrationand bodyscore(mean _+ s.e.m.)duringpregnancy in 8 indigenousgna~s.DK = day of kidding. RESULTS
Fig. I shows the mean ( _ s.e.m.) plasma progesterone concentration and body condition during pregnancy in 8 goats in which blood samples were collected throughout gestation. Mean (4- s.e.m.) duration of pregnancy was 146.7 4- 3.0 days, and 75% were carrying twins. Plasma progesterone concentrations rose to above 4-0 ng/ml by day 10 and were maintained at this level until day 40 of pregnancy. This was followed by a significant rise in mean progesterone concentration from 3.91 4- 0.51 ng/ml on day 40 to 5-96 4- 0.51 ng/ml on day 60 (P < 0.05, Student's t-test). Progesterone concentrations remained high until 5 days before kidding then fell sharply. In 5 goats progesterone concentrations were 0-8 ng/ml on the day of kidding and in 2 goats progesterone values were still high, i.e. 1.5 ng/ml. One goat was not bled on the day of kidding. Mean ( _ s.e.m.) condition scores improved from 2-4 _ 0.2 (good) to 2-8 4- 0.2 (very good) over the first 80 days of pregnancy and were maintained at 2.8 until 45 days before kidding. From then until kidding, mean condition scores fell to 2.2 4- 0-2 (fair). Fig. 2 shows the mean (4- s.e.m.) plasma progesterone concentrations in the pseudopregnant goats. There was an increase in plasma progesterone concentrations between days 35 and days 60, as in the pregnant goats, but this rise was not significant. Unlike the pregnant goats, plasma progesterone concentrations returned gradually to basal over the last 50 days. No clinical signs of hydrometra or endometritis were observed. Fig. 3 gives the mean (4- s.e.m~) change in body weight and body condition in 12 does post partum. Goats lost weight and condition over the first 35 days post parturn with mean scores falling from 2.2 4- 0.2 to 1.9 4- 0. I and mean weights falling from 36.9 4- 1-9 to 32. I _ 2"0 kg during this period. Mean body condition scores did not rise above 2.0 until after day 1lOpostpartum, and had reached 2-5 by day 150. Weight regain was correspondingly slow; by day 150 weights were still below those recorded immediately after parturition. Onset of ovarian activity was defined as the first sustained rise in plasma progesterone to > 2.0 ng/ml. Fig. 3 shows the cumulative percentage of goats cycling against days post-kidding. The mean interval from
PROGESTERONEAND REPRODUCTIVECYCLE
245
P (nglml)
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FIG. 2. Changes in plasma progesteroneconcentration (mean __+s.e.m.) during pseudopregnancy in 3 indigenous goats. OO = day progesteroneconcentration returned to basal. kidding to onset ofcyclicity was 97.3 __+ 9.5 days and ranged from 28 to 133 days. On average, return to ovarian cyclicity took place before body condition and weights had returned to normal and coincided with weaning. Seven goats commenced ovarian activity 20.3 _+ 3.1days after weaning, and 5 goats showed ovarian activity 33.6 _+ 4.8 days before weaning. The mean interval to onset of ovarian activity was shorter for goats kidding in April to July (82-7 _+ 16.0 days, n = 6), compared with goats kidding between October and November (112 _+ 7.3days, n = 6), but this difference was not significant. The first cycle length was 19-5 _+ 0.6days (range 15 to 22) and was preceded by a small rise in progesterone in only one goat. D I S C U S S I O N
The mean gestation period in this study was 147 days, which agrees with the value of 146days (range 143 to 153 days) as reviewed by Devendra and Burns (1983) for various tropical breeds of goat. Progesterone concentrations during pregnancy were maintained at around 4 to 5 ng/ml for the first 40 days o f pregnancy, values typical 2.5
1.5 40
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FIG. 3. Relationshipbctwconchange in body score and weight (mean + s.e.m.) and cumulative percentage of goats (n = 12) showing ovarian activitypost partum. DK -- day of kidding.
246
LLEWELYN, OGAA AND OBWOLO
of the luteal phase in non-pregnant goats (Llewetyn et al., 1987). Between days 40 and 60 of gestation, progesterone concentrations increased significantly to around 6 ng/ ml. This rise could be due to stimulation of progesterone synthesis by caprine placental lactogen which is secreted from day 44 onwards (Currie et al., 1977; Currie et al., 1990). Placental lactogen levels depend on the number of foetuses present (Hayden et al., 1980) and so in this study, where most of the goats were carrying twins the rise in progesterone may have been more marked. The present findings agree with those of Thorburn and Schneider, (1972), who found that the rise in progesterone seen after day 40 was greater in goats bearing twins as opposed to singletons. In contrast, Humblot et al. (1990) did not find any significant rise in progesterone or relationship between number of foetuses and progesterone concentrations during pregnancy. It is not clear if the increase in plasma progesterone seen after day 40 of pregnancy in this study is of luteal or placental origin. Histologically, the granulosa-derived luteal cells show evidence of greater secretory activity at this time (Harrison, 1948) and the corpus luteum is a major source of progesterone throughout pregnancy (Linzell and Heap, 1968). The placenta, although unable to synthesise sufficient progesterone to maintain pregnancy in ovariectomised goats (Meites et aL, 1951; Sheldrick et al., 1980) does contribute towards progesterone production during the latter half of pregfiancy. However, most of the progesterone produced by the placenta is metabolised to pregnanediol (Heap and Flint, 1984). In this study, changes in progesterone concentration throughout pseudopregnancy are reported for the first time, albeit in only 3 animals. Progesterone levels over the first 40 days were comparable to those of pregnant goats, agreeing with Humblot et al. (1990), who measured progesterone concentrations from days 15 to 27 in 2 pseudopregnant goats. In this study, progesterone levels rose between days 40 and 60, but unlike the pregnant goats, this was not significant. There was a gradual fall in progesterone from day 100 onwards, comparable to the pattern seen in pregnant goats hysterectomised on day 40 (Currie and Thorburn, 1974). These profiles are consistent with pregnancy followed by early embryonic death. Measurement of pregnancyspecific protein B concentrations in plasma would have enabled a distinction to be made between pseudopregnancy and pregnancy followed by embryonic mortality (Humblot et al., 1990). Although well documented, the cause of pseudopregnancy in the goat is not well understood (Smith, 1986). Sometimes extended luteal function is accompanied by hydrometra (Pieterse and Taverne, 1986) and cloudburst (Smith, 1986), but often there is persistent luteal function in the absence of any signs of hydrometra or clinical endometritis (C. A. Llewelyn, unpub, data). The evidence to date suggests that accumulation of fluid in the uterus is the result of, and not the cause of prolonged luteal function (Pieterse and Taverne, 1986). In the goat, prostaglandin F2~ (PGF2~), produced by the uterus in a pulsatile manner, is responsible for luteolysis (Cook and Homeida, 1985; Battye et al., 1988). Oxytocin, secreted by the large granulosa-derived cells of the corpus luteum (Kiem et al., 1989), also exerts a luteolytic action, possibly mediated via uterine PGF2~ synthesis (Cook and Homeida, 1983; 1984; 1985). A feedback mechanism may exist whereby PGF2~ stimulates luteal oxytocin release which in turn increases uterine PGF2~ secretion as proposed for sheep (Flint and Sheldrick, 1983). Impaired luteal oxytocin production, or disruption of the rise in uterine oxytocin receptors during luteolysis (Jenner et aL, 1991) might interfere with PGF2~ release resulting in persistence of the corpus luteum. Administration of oxytocin was as effective as PGF2~ in bringing about luteolysis in pseudopregnant goats (Pieterse and Taverne, 1986). Increased secretion of a luteotrophin may also
PROGESTERONE AND REPRODUCTIVE CYCLE
247
play a role in the aetiology of pseudopregnancy. During the oestrous cycle both LH and prolactin probably act synergistically as lutdotrophins (Buttle, 1983) and prolactin concentrations are often elevated during pseudopregnancy (Taverne et aL, 1990). Treatment with bromocriptine for 6-10 days lowered prolactin concentrations and resolved pseudopregnancy in 5/7 goats (Taverne et al., 1988; Taverne et al., 1990). The mean interval between kidding and onset of ovarian activity was 97 days, when concentrate supplement was provided to goats during pregnancy and lactation. This shows that there is considerable scope for improvement of goats kept in communal areas, which remain anoestrus after kidding for around 150 days (Hale, 1986). The latter are herded during the day and kraaled at night and do not usually receive supplements. The limited amount of time available for browsing, seasonal changes in the quality of herbage and heavy burdens of parasites have been cited as factors prolonging lactational anoestrus (Hale, 1986). It is likely that dietary supplementation, using locally available agricultural by-products, could contribute to reducing kidding intervals and improving productivity of indigenous goats in Zimbabwe. In this study, the initial increase in body condition during the early part of pregnancy was not maintained through to kidding. As most goats were carrying twins they might have benefited from a higher level of supplementation during the last 40 days of gestation. Despite an increased feed intake, goats lost weight and body condition during the first 35 days of lactation, when milk yields are rising to maximal (Kala and Prakash, 1990). Loss in weight and condition are known to regulate the length of lactational anoestrus in cows (Butler et al., 1981; Staples and Thatcher, 1990), and these effects are most probably due to changes in energy status (Canfield and Butler, 1990). Cows are in negative energy balance during the early post-partum period when increased feed consumption cannot match the metabolic demands of lactation. The mechanism whereby ovarian activity is suppressed is not clear but various metabolic signals, such as reduced blood glucose (Rutter and Manns, 1987) may act on the hypothalamic-pituitary axis to reduce gonadotrophin secretion (Peters and Lamming, 1990). In this study, ovarian activity commenced just before body weight and condition started to improve, at a time when the goats would have returned to a positive energy balance. Suckling may also have been an important factor in regulating the return to ovarian activity post partum in this study, since the mean time to onset of ovarian activity coincided with mean time to weaning. Whilst the precise nature of the mechanisms responsible for lactational anoestrus are not known, the evidence available suggests there is a reduction in hypothalamic gonadotrophin-releasing hormone (GnRH), leading to a deficiency in pituitary gonadotrophin secretion (Peters and Lamming, 1990). Suckling appears to inhibit reproductive activity by afferent inputs other than those due to teat stimulation, which decrease hypothalamic G n R H release (Williams, 1990). The neural pathways involved are not clearly defined, but may have endogenous opioid peptides as neurotransmitters (Whisnant et al., 1986; Malven et al., 1986; Cross et al., 1987). Abrupt weaning can increase pulsatile LH secretion and may result in ovulation and resumption of ovarian activity (Shively and Williams, 1989). In this study, all 7 goats which were still in anoestrus at the time of weaning, ovulated within 20 days of kid removal. This supports the hypothesis that in this species suckling contributes to inhibiting LH release post partum. Further studies are necessary to see whether restricted suckling or early weaning would shorten lactational anoestrus. In the present study, goats which kidded in April to July resumed ovarian activity sooner than those kidding in October to February. This difference was not significant,
248
LLEWELYN, OGAA AND OBWOLO
probably because of the small sample size and large sample variation. The results are consistent with those obtained previously (Ndlovu and Llewelyn, unpub, data), in which does kidding in March to April had a mean kidding interval significantly shorter than those kidding in August to December (265 + 48 days v s 382 + 90 days, P < 0.01). It is possible that this difference was due to nutritional factors, since there is generally more forage available in March to April at the end of the rainy season. Further studies are needed to see if there is a correlation between season of kidding and length of post-partum anoestrus, as has been reported in the cow (Peters and Riley, 1982). ACKNOWLEDGEMENTS
This work was supported by the University of Zimbabwe Research Board. Dr Llewelyn was in receipt of a Beit Trust (UK) Medical Research FeUowship tenable through the Royal (Dick) School of Veterinary Studies, Edinburgh. The Wellcome Trust and the International Atomic Energy Agency are thanked for providing some additional financial support. Dr C. T. Kadzere is thanked for reading the manuscript. Accepted for publication January 1992 REFERENCES BATTVE,K. M., FAIRCLOUGH,R. J., CAMERON,A. W. N. & TROUNSEN,A. O. (1988). Journal of Reproduction and Fertility, 84, 425--4.30. BUTLER,W. R., EVERETT,R. W. & COPPOCK,C. E. (1981). Journal of Animal Science, 53, 742-748. Btrrrlm, H. L. (1983). Journal of Physiology, 342, 399-407. CANFIELD, R: W. & BtrrLrr.R, W. R. (1990). Domestic Animal Endocrinology, 7, 323-330. COOK, R. G. & HOtaEIDA,A. M. (1983). Theriogenology, 20, 363-365. COOK, R. G. & HOMEIDA,A. M. (1984). Research in Veterinary Science, 36, 48-51. COOK, R. G. & HOMEIDA,A. M. (1985). Journal of Reproduction and Fertility, 75, 63-68. CORRm, J. E. T., RATeLIEFE,W. A. & McP',-mRSON,J. S. (1981). Clinical Chemistry, 27, 594-599. CURRIE, W. B. & THORaURN,G. D. (1974). Journal of Reproduction and Fertility, 41, 501-504. CURRIE, W. B., KELLY,P. A., FRIESEN,H. G. & THORnURN,G. D. (1977). Journal of Endocrinology, 73, 215-226. CURmE, W. B., CARD,C. E., MICHEL,F. J. & IGNOTZ,J. (1990). Journal of Reproduction and Fertility, 90, 25-36. CROSS, J. C., RI.rrTER,L. M. & MANNS,J. G. (1987). Domestic Animal Endocrinology, 4, I 1I-I 12. DEVENDRA,C. & BURNS,M. (1983). Goat Production in the Tropics. 2nd edn. Commonwealth Agricultural Bureaux, Farnham Royal. pp 74-89. FLINT, A. P. F. & SHELDRICK,E. L. (1983). Journal of Reproduction and Fertility, 67, 215-225. HALE, D. (1986). Potential of Small Ruminants in Eastern and Southern Africa. (Eds Kategele and Adenige.) Joint OAU/IBAR/IDRC Workshop, Nairobi. pp 181-198. HARRISON,R. J. (1948). Journal of Anatomy, 82, 21-48. HAYDEN,T. J., THOMAS,C. R., SMITH,S. V. & FORSYTH,I. A. (1980). Journal of Endocrinology, 86, 279-290. HEAP, R. B. & FLINT,A. P. F. (1984). Reproduction in mammals 3: Hormonal control of reproduction. 2nd edn. (Eds C. R. Austin and R. V. Short). Cambridge University Press. pp 153-194. HONHOLD,N., PETIT,H. & HALLIWELL,R. W. (1989). TropiealAnimalHealth and Production, 21, 121-127. HUMBLOT,P., MONTIGNYDE, G., JEANGUYOT,N., TETEDOIE,F., PAYEN,B., THIBIER,M. & SASSER,R. G. (1990). Journal of Reproduction and Fertility, 89, 205-212. JENNER, L. J., PARKINSON,T. J. & LAMMING,G. E. (1991). Journal of Reproduction and Fertility, 91, 49-38. KALA, S. N. & PRAKASH,B, (1990). Small Ruminant Research, 3, 475-484. KIEM, D. J., WALTERS,D. L., DANIEL, S. A. & ARMSTRONG,D. T. (1989). Journal of Reproduction and Fertility, 87, 485-493. LINZELL,J. J. & HEAP, R. B. (1968). Journal of Endocrinology, 41, 443-..448. LLEWl/LYN,C. A., LUCKINS,A. G., MUNRO, C. B. & PERRIE,J. (1987). British Veterinary Journal, 143, 423-431. MALVEN,P. V., PARF'~-'TJ. , R., GREC-,(3,D. W., ALl.RICH,R. D. & MOSS,G. E. (1986). Journal of Animal Science, 62, 723-733. MEtrE.S,J., WEBSTER,H. D., YOUNG,F. W., THORP, F. & HATCH,R. N. (1951). Journal of Animal Science, 10, 411-416.
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PETERS, A. R. & LAMMING, G. E. (1990). Oxford Reviews of Reproductive Biology. Vol I2. (Ed. S. R. Milligan). pp 245-288. PETERS, A. R. & RILEY, G. M. (1982). British Veterinary Journal, 138, 533-537. Pa~rea~sE, M. C. & T^wm~rE, M. A. M., (1986). Theriogenology, 6, 813-821. R u T r ~ , L. M. & MANNS, J. G. (1987). Journal of Animal Science, 64, 479--488. SH~t.DRICIC, E. L., Riclc~rrs, A. P. & FLINT, A. P. F. (1980). Journal of Reproduction and Fertility, 60, 399-348. SmVEL',', T. E. & WII.LIAMS, G. L. (1989). Domestic Animal Endocrinology, 6, 379-387. SMm-I, M. C. (1986). Current Therapy in Theriogenology. (Ed. D. A. Morrow). Saunders, Philadelphia, London. pp 585-586. STAPLe, C. R. & THATCH~, W. W. (1990). Journal of Dairy Science,53, 938-947. TAVI~RI,~,M. A. M., BEVERS,M. M. & VAN D~. BP.ANDE,H. J. (1990). JournalofReproduction and Fertility, Abstract Series No 5, (No 28). p 19. TAVER~re,M. A. M., LAVOm, M. C., BEV~RS,M. M., PmT~RSE,M. C. & DmLEMAS, S. J. (1988). Theriogenology, 30, 777-783. THORBU~N, G. D. & SCHNEXDE~,W. (1972). Journal of Endocrinology, 52, 23-36. WHISNAm', C.S., KISER, T. E., THOMPSON, F. N. & BARe, C. R. (1986). Journal of Animal Science, 63, 561-564. W~LtJAMS, G. L. (1990). Journal of Animal Science, 68, 831-852. CONCENTRATION EN PROGESTERONE PLASMATIQUE DURANT LA GESTATION ET LA PSEUDOGESTATION E T LE DEBUT DE L'ACTIVITE OVARIENNE POST PARTUM CHEZ DES CHEVRES INDIGENES AU ZIMBABWE R~sum6--Huit ch6vres gestantes ant 6t6 gard6es fi l'6table individuellement et nourries pendant route la dur6e de la gestation et de la lactation avee une ration de fain et de eoncentr6. La p6riode moyenne de gestation a 6t6 de 146J 5: 3,0jours avec un taux de g6mellit6 de 75 p. I00. L'indice de r6tat g6n6ral mesur6 avec une &:hellede points est pass6 de 2,4 + 0,2 fi 2,8 + 0,2 pendant les 80 premiers jours de la gestation et s'est maintenu A 2,8 jusqu'au 45e jour avant la mise bas. De cette date ~ la mise has, l'indice corporel est tomb6 ~ 2,2 4. 0,2. Les concentrations plasmatiques en progest6rone ant augment6 au cours de la gestation de fa~on significative, passant de 3,91 +_ 0,51 ng/ml au quaranti6mejour ~i 5,96 + 0,5I ng/ml au soixanti6me jour (P < 0,05). Elles sont rest6es 61ev6es jusqu'au cinqui6me jour avant ia mise bas. Trois ch6vres pseudogestantes avaient des profils de progest6ron6mie identiques ~iceux des gestantes au tours des 80 premiers jours, mais l'616vation aux environs des jours 35 fi 40 n'6tait pas signiflcative et les concentrations sont retomb6es progressivement aux niveaux de base apr6s le 100ejour. Les m6mes huit femelles, ainsi que quatre autres qui avaient 6t6 introduites en plus 60 ~ 70 jours avant la mise bas, ant 6t6 utilis6es pour 6tudier le d6but de l'activit6 ovariennepostpartum. Le taux de g6mellit6 6tait de 83 p. I00. L'indice moyen delaconditioncorporelleaumomentdelapartudtion&aitde2,2 _ O,1.Au35ejourpostpartumcetindice moyen 6tait tomb6 ~t 1,9 + 0,I et les poids moyens &aient pass6s de 36,9 4- 1,9kg fi la raise has 32,1 + 2,0kg. La eyclicit6 ovarienne avait repris juste avant la reprise des indices moyens et des poids. L'intervallemoyendepuislamisebasjusqu'aud6butdel'oestrus6taitde97,3 + 9,Sjours, cequicoineidait avee le temps moyen du sevrage soit 99,5 4- 5,5 jours. L'auteur sugg6re que la t6t6e et la condition physique agissent comme des r6gulateurs de l'anoestrus post partum pour cette esp6ce. La saison peut 6galement jouer un r61e r6gulateur, &ant donn6 que les ch6vres qui ant mis bas entre avril et juin (n = 6) &aient en anoestrus pendant 82,7 + 15,0 jours, donn6e A comparer ~ 112 + 7,3 jours pour celles qui ant mis bas d'octobre ~ f6vder (n = 6), quoique la diff6rence ne ffit pas significative. CONCENTRACION DE PROGESTERONA EN EL PLASMA DURANTE LA PRENEZ Y PSEUDOPRENEZ E INICIO DE LA ACTIVIDAD OVARICA POS-PARTO EN CABRAS NATIVAS EN ZIMBABWE Resumen---Se, estabularon individualmente ocho cabras prefiadas, d~ndoles heno y concentrados tanto durante la prefiez, coma durante la lactaci6n. El promedio de gestaci6n rue 146.7 + 3'0 dins, con una tasa gemelar de 75 par ciento. La media de condici6n corporal, mejor6 de 2.4 4- 0"2 a 2-8 + 0.2 durante los pdmeros 80 dias de gestaci6n y se mantuvo en 2.8 hasta el din 45 antes del parto, cayendo a 2-2 + 0.2 de ahi en adelante. La concentraci6n de progesterona en el plasma durante la prefiez, subi6 significativamente de 3.91 + 0-51 ng/ml el din 40 a 5.96 + 0"51 ng/ml el dia 60 (P < 0.05), permaneciendo alta hasta 5 dias antes del parto. Tres cabras pseudoprefiadas tuvieron niveles de progesterona similares a aquellos de las cabras prefiadas, durante los primeros 80 dias, pero el aumento alrededor del din 35 a 40 no rue signifieativo y los niveles de progesterona retornaron gradualmente a los niveles basales, despu6s del dia 100. Las mismas 8 cabras, junto con 4 adicionales, que habian sido traidas 60 y 70 dias antes del parto, fueron utilizadas para estudiar el inicio pos-parto de la actividad ov~rica. E1 porcentaje gemetar rue de 83
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LLEWELYN, OGAA AND OBWOLO
por ciento. La condiei6n corporal media al parto fue de 2"2 + 0.1. Para el dia 35 pos-parto, la condici6n corporal media habia ealdo a 1-9 _+ 0.1; los pesos medios de 36.9 + 1.9 al parto, eayeron a 32.1 -I- 2.0 kg. La eielieidad ov~dea se reanud6 un poeo despu~s de que la eondieibn corporal y los pesos mejoraron. El intervalo promedio desde el parto hasta el eomienzo de los ciclosestrales rue de 97.3 + 9.5 dias. Se sugiere que el amamantamiento y la eondiei6n corporal regulan la apariei6n dd estro pos-parto en 6sta espeeie. La estaei6n de pariei6n pueda que juegue un papel importante, debido, a que las eabras que paderon entre abril y junio (n = 6), estuvieron en anestro por 82"7 + 15"0dlas, en eomparaei6n a 112 + 7.3 dlas para las eabras que parieron entre octubre y febrero (n --: 6), aunque la difereneia no fue estadlstieamente significativa.
UNIVERSITY OF EDINBURGH CENTRE FOR TROPICAL VETERINARY MEDICINE Diploma/MSc P O S T G R A D U A T E C O U R S E S The following courses are available: (i) Tropical Veterinary Medicine. This course is designed for field veterinarians aiming at the senior and middle ranks o f veterinary services in developing countries. It deals with the prevention and control of animal diseases at regional and national levels and has a strong epidemiological component. Related aspects of animal production and veterinary public health are also covered. (ii) Tropical Veterinary Science. This is a course for veterinarians, which is mainly concerned with the laboratory diagnosis o f diseases o f animals including poultry and wildlife in developing countries. It also includes the organisation and management o f tropical veterinary laboratories and the epidemiology of the major diseases o f animals. (iii) Tropical Animal Production and Health. This course which is organised in conjunction with the University's Department of Agriculture is open to agriculture and veterinary graduates intending to specialise in animal production in developing countries. It provides a comprehensive review of the main constraints to animal production likely to be encountered in these countries with an indication of how they may be overcome. Further information can be obtained from the Director o f the Centre for Tropical Veterinary Medicine, Easter Bush, Roslin EH25 9RG, Midlothian, Scotland.
PLASMA PROGESTERONE CONCENTRATIONS DURING PREGNANCY AND PSEUDOPREGNANCY AND ONSET OF OVARIAN ACTIVITY P O S T P A R T U M IN INDIGENOUS GOATS IN ZIMBABWE C. A. LLEWELYN1'3, J. S. OGAA 2 and M. J. OBWOLO 2 IDepartment of Animal Science and 2Faculty of Veterinary Science, University of Zimbabwe, Mount Pleasant MP 167, Harare, Zimbabwe SUMMARY
Eight pregnant does were housed individually andfed a hay and concentrate diet throughout pregnancy and lactation. The mean gestation period was 146.7 + 3.0 days, with a twinning rate of 75 per cent. Mean body condition scores improved from 2.4 + 0.2 to 2.8 + 0.2 over the first 80 days of gestation and were maintained at 2.8 uhtil 45 days before kidding. From then until kidding, mean scores fell to 2.2 +_ 0.2. Plasma progesterone concentrations during pregnancy rose significantly from 3.91 + 0"51 ng/ml on day 40 to 5.96 ++_0.51 ng/ml on day 60 (P < 0.05) and remained high until 5 days before kidding. Three pseudopregnant does had similar progesterone profiles to pregnant does over the first 80 days, but the rise around day 35 to 40 was not significant and progesterone concentrations returned gradually to basal levels after day 100. The same 8 does, together with an additional 4 does which had been brought inside 60 to 70 days before kidding, were used to study onset of ovarian activity post partum. The twinning percentage was 83 per cent. Mean body condition score at parturition was 2"2 +_ 0"1. By day 35 post partum, mean condition scores hadfallen to 1.9 + 0.1, andmean weights from 36.9 + 1.gkg at kidding to 32.1 + 2.0kg. Ovarian cyclicity was resumed just before mean scores and weights started to improve. The mean intervalfrom kidding to onset of oestrous cycles was 97.3 + 9.5 days. This coincided with mean time to weaning which was 99.5 + 5.5 days. It is suggested that suckling and body condition regulate the length of post-partum anoestrus in this species. Season may also play a regulatory role, since does kidding in April t o June (n = 6) were anoestrus for 82"7 + 15"0 days compared to 112 + 7.3 days for does kidding in October to February (n = 6), although the difference was not significant. INTRODUCTION
There are approximately 1.8 million goats in Zimbabwe which are kept by subsistence farmers in the communal areas. Despite the belief that these goats are prolific breeders, productivity is generally low. Some of the reasons for this are high kid mortality rates and prolonged kidding intervals (Hale, 1986). In one study, a mean 9 value of 370 days was recorded and plasma progesterone profiles indicated that this was due to prolonged post-partum anoestrus (Ndlovu and Llewelyn, unpub, data), with most does remaining acyclical for over 150 days. It was thought that nutritional constraints were responsible for delaying the onset of post-partum activity in these goats, resulting in prolonged kidding intervals. The present study was designed to investigate progesterone profiles during pregnancy and to investigate onset of ovarian 3Present address: c[o Croyland House,Dry Drayton, Cambridge, CB3 8BU. 242
PROGESTERONE AND REPRODUCTIVE CYCLE
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TABLE I
Ingredients of the concentrate supplementfed to goats
Constituent
% of diet
Maize meal, ground Cotton seed hulls, ether extracted High protein concentrate, 65% urea Limestone flour Sodium chloride Trace element mix ~ Vitamin A Vitamin D
59.5 30.0
Energy content Crude protein
9.9 0.5 0,05 0.01 300 I.U./kg 300 I.U./kg 10 MJ/kg 13%
t To give a final concentrationof 3mg iron, 3mg iodine, 2.5 mg zinc, 0"75mg manganeseand 0.015mg cobalt per kg feed. activity in a group of goats receiving concentrate supplementation during pregnancy and lactation. MATERIALS AND METHODS
Eleven does from the University goat herd were housed in single pens and fed a diet of reid hay ad libitum supplemented with a ration based on maize meal and cotton seed hulls (Table I). Eight does were studied throughout pregnancy and 3 throughout a pseudopregnancy. To increase the numbers of does available for studying the interval from kidding to onset of ovarian activity from 8 to 12, another 4 pregnant does of comparable body condition were fed concentrate supplement for the last 60 to 70 days of pregnancy. All does received 0.25 kg/day of the concentrate ration, which was increased after parturition to 0-5 kg and to 1 kg/day for body condition scores of ~ 1.5. The goats were weighed weekly and scored 3 times a week to assess body condition using the method of Honhold et ak 0989). Mean interval from parturition to weaning was 99-5 _ 5.5 days (range 69 to 114). Goats were bled 3 times a week throughout the study. Blood was collected into tubes containing EDTA as anti-coagulant and kept on ice before centrifugation at 2,500g for 30minutes. Plasma was stored at -20~ to await radioimmunoassay (RIA). Progesterone concentrations were measured in 50/A plasma by a direct doubleantibody RIA according to the method of Corrie et aL (1981) with 2.5 pg of 125iodinated progesterone-lla-glucuronide-tyramine (Amersham International) as tracer and 500 ng/tube of danazol (Winthrop Sterling) to displace progesterone bound to plasma proteins. The first antiserum (R104/10) was raised in a rabbit against progesterone1la-hemisuc.~inate conjugated to bovine serum albumin and used at a titre of 1/4000. Cross reactions were as follows: ~lla-hydroxyprogesterone 15-9%, corticosterone 4.6%, deoxycorfisone 3.1%, 5a-pregnanedione 1-6%, l l-dehydrocorticosterone 1.2%, 17a-hydroxyprogesterone 0.6%, pregnenolone and oestrone < 0-1%. Cortisol, cortisone, androstenedione and testosterone were < 0-01% and oestradiol and oestriol < 0.001 per cent. The second antiserum was donkey anti-rabbit serum used with normal rabbit serum as carrier. The minimal detectable dose was 0.4 ng/ml and the intra-assay coefficient of variation was 14-1% and 10.7% for medium (2-4 ng/ml) and high (4"8 ng/ml) quality control pools respectively.
LLEWELYN, O G A A A N D O B W O L O
244 Body scocP
8
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:
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(days)
FIG. 1. Changesin plasmaprogesteroneconcentrationand bodyscore(mean _+ s.e.m.)duringpregnancy in 8 indigenousgna~s.DK = day of kidding. RESULTS
Fig. I shows the mean ( _ s.e.m.) plasma progesterone concentration and body condition during pregnancy in 8 goats in which blood samples were collected throughout gestation. Mean (4- s.e.m.) duration of pregnancy was 146.7 4- 3.0 days, and 75% were carrying twins. Plasma progesterone concentrations rose to above 4-0 ng/ml by day 10 and were maintained at this level until day 40 of pregnancy. This was followed by a significant rise in mean progesterone concentration from 3.91 4- 0.51 ng/ml on day 40 to 5-96 4- 0.51 ng/ml on day 60 (P < 0.05, Student's t-test). Progesterone concentrations remained high until 5 days before kidding then fell sharply. In 5 goats progesterone concentrations were 0-8 ng/ml on the day of kidding and in 2 goats progesterone values were still high, i.e. 1.5 ng/ml. One goat was not bled on the day of kidding. Mean ( _ s.e.m.) condition scores improved from 2-4 _ 0.2 (good) to 2-8 4- 0.2 (very good) over the first 80 days of pregnancy and were maintained at 2.8 until 45 days before kidding. From then until kidding, mean condition scores fell to 2.2 4- 0-2 (fair). Fig. 2 shows the mean (4- s.e.m.) plasma progesterone concentrations in the pseudopregnant goats. There was an increase in plasma progesterone concentrations between days 35 and days 60, as in the pregnant goats, but this rise was not significant. Unlike the pregnant goats, plasma progesterone concentrations returned gradually to basal over the last 50 days. No clinical signs of hydrometra or endometritis were observed. Fig. 3 gives the mean (4- s.e.m~) change in body weight and body condition in 12 does post partum. Goats lost weight and condition over the first 35 days post parturn with mean scores falling from 2.2 4- 0.2 to 1.9 4- 0. I and mean weights falling from 36.9 4- 1-9 to 32. I _ 2"0 kg during this period. Mean body condition scores did not rise above 2.0 until after day 1lOpostpartum, and had reached 2-5 by day 150. Weight regain was correspondingly slow; by day 150 weights were still below those recorded immediately after parturition. Onset of ovarian activity was defined as the first sustained rise in plasma progesterone to > 2.0 ng/ml. Fig. 3 shows the cumulative percentage of goats cycling against days post-kidding. The mean interval from
PROGESTERONEAND REPRODUCTIVECYCLE
245
P (nglml)
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FIG. 2. Changes in plasma progesteroneconcentration (mean __+s.e.m.) during pseudopregnancy in 3 indigenous goats. OO = day progesteroneconcentration returned to basal. kidding to onset ofcyclicity was 97.3 __+ 9.5 days and ranged from 28 to 133 days. On average, return to ovarian cyclicity took place before body condition and weights had returned to normal and coincided with weaning. Seven goats commenced ovarian activity 20.3 _+ 3.1days after weaning, and 5 goats showed ovarian activity 33.6 _+ 4.8 days before weaning. The mean interval to onset of ovarian activity was shorter for goats kidding in April to July (82-7 _+ 16.0 days, n = 6), compared with goats kidding between October and November (112 _+ 7.3days, n = 6), but this difference was not significant. The first cycle length was 19-5 _+ 0.6days (range 15 to 22) and was preceded by a small rise in progesterone in only one goat. D I S C U S S I O N
The mean gestation period in this study was 147 days, which agrees with the value of 146days (range 143 to 153 days) as reviewed by Devendra and Burns (1983) for various tropical breeds of goat. Progesterone concentrations during pregnancy were maintained at around 4 to 5 ng/ml for the first 40 days o f pregnancy, values typical 2.5
1.5 40
I
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Weiqht
(kg)
,0
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50
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FIG. 3. Relationshipbctwconchange in body score and weight (mean + s.e.m.) and cumulative percentage of goats (n = 12) showing ovarian activitypost partum. DK -- day of kidding.
246
LLEWELYN, OGAA AND OBWOLO
of the luteal phase in non-pregnant goats (Llewetyn et al., 1987). Between days 40 and 60 of gestation, progesterone concentrations increased significantly to around 6 ng/ ml. This rise could be due to stimulation of progesterone synthesis by caprine placental lactogen which is secreted from day 44 onwards (Currie et al., 1977; Currie et al., 1990). Placental lactogen levels depend on the number of foetuses present (Hayden et al., 1980) and so in this study, where most of the goats were carrying twins the rise in progesterone may have been more marked. The present findings agree with those of Thorburn and Schneider, (1972), who found that the rise in progesterone seen after day 40 was greater in goats bearing twins as opposed to singletons. In contrast, Humblot et al. (1990) did not find any significant rise in progesterone or relationship between number of foetuses and progesterone concentrations during pregnancy. It is not clear if the increase in plasma progesterone seen after day 40 of pregnancy in this study is of luteal or placental origin. Histologically, the granulosa-derived luteal cells show evidence of greater secretory activity at this time (Harrison, 1948) and the corpus luteum is a major source of progesterone throughout pregnancy (Linzell and Heap, 1968). The placenta, although unable to synthesise sufficient progesterone to maintain pregnancy in ovariectomised goats (Meites et aL, 1951; Sheldrick et al., 1980) does contribute towards progesterone production during the latter half of pregfiancy. However, most of the progesterone produced by the placenta is metabolised to pregnanediol (Heap and Flint, 1984). In this study, changes in progesterone concentration throughout pseudopregnancy are reported for the first time, albeit in only 3 animals. Progesterone levels over the first 40 days were comparable to those of pregnant goats, agreeing with Humblot et al. (1990), who measured progesterone concentrations from days 15 to 27 in 2 pseudopregnant goats. In this study, progesterone levels rose between days 40 and 60, but unlike the pregnant goats, this was not significant. There was a gradual fall in progesterone from day 100 onwards, comparable to the pattern seen in pregnant goats hysterectomised on day 40 (Currie and Thorburn, 1974). These profiles are consistent with pregnancy followed by early embryonic death. Measurement of pregnancyspecific protein B concentrations in plasma would have enabled a distinction to be made between pseudopregnancy and pregnancy followed by embryonic mortality (Humblot et al., 1990). Although well documented, the cause of pseudopregnancy in the goat is not well understood (Smith, 1986). Sometimes extended luteal function is accompanied by hydrometra (Pieterse and Taverne, 1986) and cloudburst (Smith, 1986), but often there is persistent luteal function in the absence of any signs of hydrometra or clinical endometritis (C. A. Llewelyn, unpub, data). The evidence to date suggests that accumulation of fluid in the uterus is the result of, and not the cause of prolonged luteal function (Pieterse and Taverne, 1986). In the goat, prostaglandin F2~ (PGF2~), produced by the uterus in a pulsatile manner, is responsible for luteolysis (Cook and Homeida, 1985; Battye et al., 1988). Oxytocin, secreted by the large granulosa-derived cells of the corpus luteum (Kiem et al., 1989), also exerts a luteolytic action, possibly mediated via uterine PGF2~ synthesis (Cook and Homeida, 1983; 1984; 1985). A feedback mechanism may exist whereby PGF2~ stimulates luteal oxytocin release which in turn increases uterine PGF2~ secretion as proposed for sheep (Flint and Sheldrick, 1983). Impaired luteal oxytocin production, or disruption of the rise in uterine oxytocin receptors during luteolysis (Jenner et aL, 1991) might interfere with PGF2~ release resulting in persistence of the corpus luteum. Administration of oxytocin was as effective as PGF2~ in bringing about luteolysis in pseudopregnant goats (Pieterse and Taverne, 1986). Increased secretion of a luteotrophin may also
PROGESTERONE AND REPRODUCTIVE CYCLE
247
play a role in the aetiology of pseudopregnancy. During the oestrous cycle both LH and prolactin probably act synergistically as lutdotrophins (Buttle, 1983) and prolactin concentrations are often elevated during pseudopregnancy (Taverne et aL, 1990). Treatment with bromocriptine for 6-10 days lowered prolactin concentrations and resolved pseudopregnancy in 5/7 goats (Taverne et al., 1988; Taverne et al., 1990). The mean interval between kidding and onset of ovarian activity was 97 days, when concentrate supplement was provided to goats during pregnancy and lactation. This shows that there is considerable scope for improvement of goats kept in communal areas, which remain anoestrus after kidding for around 150 days (Hale, 1986). The latter are herded during the day and kraaled at night and do not usually receive supplements. The limited amount of time available for browsing, seasonal changes in the quality of herbage and heavy burdens of parasites have been cited as factors prolonging lactational anoestrus (Hale, 1986). It is likely that dietary supplementation, using locally available agricultural by-products, could contribute to reducing kidding intervals and improving productivity of indigenous goats in Zimbabwe. In this study, the initial increase in body condition during the early part of pregnancy was not maintained through to kidding. As most goats were carrying twins they might have benefited from a higher level of supplementation during the last 40 days of gestation. Despite an increased feed intake, goats lost weight and body condition during the first 35 days of lactation, when milk yields are rising to maximal (Kala and Prakash, 1990). Loss in weight and condition are known to regulate the length of lactational anoestrus in cows (Butler et al., 1981; Staples and Thatcher, 1990), and these effects are most probably due to changes in energy status (Canfield and Butler, 1990). Cows are in negative energy balance during the early post-partum period when increased feed consumption cannot match the metabolic demands of lactation. The mechanism whereby ovarian activity is suppressed is not clear but various metabolic signals, such as reduced blood glucose (Rutter and Manns, 1987) may act on the hypothalamic-pituitary axis to reduce gonadotrophin secretion (Peters and Lamming, 1990). In this study, ovarian activity commenced just before body weight and condition started to improve, at a time when the goats would have returned to a positive energy balance. Suckling may also have been an important factor in regulating the return to ovarian activity post partum in this study, since the mean time to onset of ovarian activity coincided with mean time to weaning. Whilst the precise nature of the mechanisms responsible for lactational anoestrus are not known, the evidence available suggests there is a reduction in hypothalamic gonadotrophin-releasing hormone (GnRH), leading to a deficiency in pituitary gonadotrophin secretion (Peters and Lamming, 1990). Suckling appears to inhibit reproductive activity by afferent inputs other than those due to teat stimulation, which decrease hypothalamic G n R H release (Williams, 1990). The neural pathways involved are not clearly defined, but may have endogenous opioid peptides as neurotransmitters (Whisnant et al., 1986; Malven et al., 1986; Cross et al., 1987). Abrupt weaning can increase pulsatile LH secretion and may result in ovulation and resumption of ovarian activity (Shively and Williams, 1989). In this study, all 7 goats which were still in anoestrus at the time of weaning, ovulated within 20 days of kid removal. This supports the hypothesis that in this species suckling contributes to inhibiting LH release post partum. Further studies are necessary to see whether restricted suckling or early weaning would shorten lactational anoestrus. In the present study, goats which kidded in April to July resumed ovarian activity sooner than those kidding in October to February. This difference was not significant,
248
LLEWELYN, OGAA AND OBWOLO
probably because of the small sample size and large sample variation. The results are consistent with those obtained previously (Ndlovu and Llewelyn, unpub, data), in which does kidding in March to April had a mean kidding interval significantly shorter than those kidding in August to December (265 + 48 days v s 382 + 90 days, P < 0.01). It is possible that this difference was due to nutritional factors, since there is generally more forage available in March to April at the end of the rainy season. Further studies are needed to see if there is a correlation between season of kidding and length of post-partum anoestrus, as has been reported in the cow (Peters and Riley, 1982). ACKNOWLEDGEMENTS
This work was supported by the University of Zimbabwe Research Board. Dr Llewelyn was in receipt of a Beit Trust (UK) Medical Research FeUowship tenable through the Royal (Dick) School of Veterinary Studies, Edinburgh. The Wellcome Trust and the International Atomic Energy Agency are thanked for providing some additional financial support. Dr C. T. Kadzere is thanked for reading the manuscript. Accepted for publication January 1992 REFERENCES BATTVE,K. M., FAIRCLOUGH,R. J., CAMERON,A. W. N. & TROUNSEN,A. O. (1988). Journal of Reproduction and Fertility, 84, 425--4.30. BUTLER,W. R., EVERETT,R. W. & COPPOCK,C. E. (1981). Journal of Animal Science, 53, 742-748. Btrrrlm, H. L. (1983). Journal of Physiology, 342, 399-407. CANFIELD, R: W. & BtrrLrr.R, W. R. (1990). Domestic Animal Endocrinology, 7, 323-330. COOK, R. G. & HOtaEIDA,A. M. (1983). Theriogenology, 20, 363-365. COOK, R. G. & HOMEIDA,A. M. (1984). Research in Veterinary Science, 36, 48-51. COOK, R. G. & HOMEIDA,A. M. (1985). Journal of Reproduction and Fertility, 75, 63-68. CORRm, J. E. T., RATeLIEFE,W. A. & McP',-mRSON,J. S. (1981). Clinical Chemistry, 27, 594-599. CURRIE, W. B. & THORaURN,G. D. (1974). Journal of Reproduction and Fertility, 41, 501-504. CURRIE, W. B., KELLY,P. A., FRIESEN,H. G. & THORnURN,G. D. (1977). Journal of Endocrinology, 73, 215-226. CURmE, W. B., CARD,C. E., MICHEL,F. J. & IGNOTZ,J. (1990). Journal of Reproduction and Fertility, 90, 25-36. CROSS, J. C., RI.rrTER,L. M. & MANNS,J. G. (1987). Domestic Animal Endocrinology, 4, I 1I-I 12. DEVENDRA,C. & BURNS,M. (1983). Goat Production in the Tropics. 2nd edn. Commonwealth Agricultural Bureaux, Farnham Royal. pp 74-89. FLINT, A. P. F. & SHELDRICK,E. L. (1983). Journal of Reproduction and Fertility, 67, 215-225. HALE, D. (1986). Potential of Small Ruminants in Eastern and Southern Africa. (Eds Kategele and Adenige.) Joint OAU/IBAR/IDRC Workshop, Nairobi. pp 181-198. HARRISON,R. J. (1948). Journal of Anatomy, 82, 21-48. HAYDEN,T. J., THOMAS,C. R., SMITH,S. V. & FORSYTH,I. A. (1980). Journal of Endocrinology, 86, 279-290. HEAP, R. B. & FLINT,A. P. F. (1984). Reproduction in mammals 3: Hormonal control of reproduction. 2nd edn. (Eds C. R. Austin and R. V. Short). Cambridge University Press. pp 153-194. HONHOLD,N., PETIT,H. & HALLIWELL,R. W. (1989). TropiealAnimalHealth and Production, 21, 121-127. HUMBLOT,P., MONTIGNYDE, G., JEANGUYOT,N., TETEDOIE,F., PAYEN,B., THIBIER,M. & SASSER,R. G. (1990). Journal of Reproduction and Fertility, 89, 205-212. JENNER, L. J., PARKINSON,T. J. & LAMMING,G. E. (1991). Journal of Reproduction and Fertility, 91, 49-38. KALA, S. N. & PRAKASH,B, (1990). Small Ruminant Research, 3, 475-484. KIEM, D. J., WALTERS,D. L., DANIEL, S. A. & ARMSTRONG,D. T. (1989). Journal of Reproduction and Fertility, 87, 485-493. LINZELL,J. J. & HEAP, R. B. (1968). Journal of Endocrinology, 41, 443-..448. LLEWl/LYN,C. A., LUCKINS,A. G., MUNRO, C. B. & PERRIE,J. (1987). British Veterinary Journal, 143, 423-431. MALVEN,P. V., PARF'~-'TJ. , R., GREC-,(3,D. W., ALl.RICH,R. D. & MOSS,G. E. (1986). Journal of Animal Science, 62, 723-733. MEtrE.S,J., WEBSTER,H. D., YOUNG,F. W., THORP, F. & HATCH,R. N. (1951). Journal of Animal Science, 10, 411-416.
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PETERS, A. R. & LAMMING, G. E. (1990). Oxford Reviews of Reproductive Biology. Vol I2. (Ed. S. R. Milligan). pp 245-288. PETERS, A. R. & RILEY, G. M. (1982). British Veterinary Journal, 138, 533-537. Pa~rea~sE, M. C. & T^wm~rE, M. A. M., (1986). Theriogenology, 6, 813-821. R u T r ~ , L. M. & MANNS, J. G. (1987). Journal of Animal Science, 64, 479--488. SH~t.DRICIC, E. L., Riclc~rrs, A. P. & FLINT, A. P. F. (1980). Journal of Reproduction and Fertility, 60, 399-348. SmVEL',', T. E. & WII.LIAMS, G. L. (1989). Domestic Animal Endocrinology, 6, 379-387. SMm-I, M. C. (1986). Current Therapy in Theriogenology. (Ed. D. A. Morrow). Saunders, Philadelphia, London. pp 585-586. STAPLe, C. R. & THATCH~, W. W. (1990). Journal of Dairy Science,53, 938-947. TAVI~RI,~,M. A. M., BEVERS,M. M. & VAN D~. BP.ANDE,H. J. (1990). JournalofReproduction and Fertility, Abstract Series No 5, (No 28). p 19. TAVER~re,M. A. M., LAVOm, M. C., BEV~RS,M. M., PmT~RSE,M. C. & DmLEMAS, S. J. (1988). Theriogenology, 30, 777-783. THORBU~N, G. D. & SCHNEXDE~,W. (1972). Journal of Endocrinology, 52, 23-36. WHISNAm', C.S., KISER, T. E., THOMPSON, F. N. & BARe, C. R. (1986). Journal of Animal Science, 63, 561-564. W~LtJAMS, G. L. (1990). Journal of Animal Science, 68, 831-852. CONCENTRATION EN PROGESTERONE PLASMATIQUE DURANT LA GESTATION ET LA PSEUDOGESTATION E T LE DEBUT DE L'ACTIVITE OVARIENNE POST PARTUM CHEZ DES CHEVRES INDIGENES AU ZIMBABWE R~sum6--Huit ch6vres gestantes ant 6t6 gard6es fi l'6table individuellement et nourries pendant route la dur6e de la gestation et de la lactation avee une ration de fain et de eoncentr6. La p6riode moyenne de gestation a 6t6 de 146J 5: 3,0jours avec un taux de g6mellit6 de 75 p. I00. L'indice de r6tat g6n6ral mesur6 avec une &:hellede points est pass6 de 2,4 + 0,2 fi 2,8 + 0,2 pendant les 80 premiers jours de la gestation et s'est maintenu A 2,8 jusqu'au 45e jour avant la mise bas. De cette date ~ la mise has, l'indice corporel est tomb6 ~ 2,2 4. 0,2. Les concentrations plasmatiques en progest6rone ant augment6 au cours de la gestation de fa~on significative, passant de 3,91 +_ 0,51 ng/ml au quaranti6mejour ~i 5,96 + 0,5I ng/ml au soixanti6me jour (P < 0,05). Elles sont rest6es 61ev6es jusqu'au cinqui6me jour avant ia mise bas. Trois ch6vres pseudogestantes avaient des profils de progest6ron6mie identiques ~iceux des gestantes au tours des 80 premiers jours, mais l'616vation aux environs des jours 35 fi 40 n'6tait pas signiflcative et les concentrations sont retomb6es progressivement aux niveaux de base apr6s le 100ejour. Les m6mes huit femelles, ainsi que quatre autres qui avaient 6t6 introduites en plus 60 ~ 70 jours avant la mise bas, ant 6t6 utilis6es pour 6tudier le d6but de l'activit6 ovariennepostpartum. Le taux de g6mellit6 6tait de 83 p. I00. L'indice moyen delaconditioncorporelleaumomentdelapartudtion&aitde2,2 _ O,1.Au35ejourpostpartumcetindice moyen 6tait tomb6 ~t 1,9 + 0,I et les poids moyens &aient pass6s de 36,9 4- 1,9kg fi la raise has 32,1 + 2,0kg. La eyclicit6 ovarienne avait repris juste avant la reprise des indices moyens et des poids. L'intervallemoyendepuislamisebasjusqu'aud6butdel'oestrus6taitde97,3 + 9,Sjours, cequicoineidait avee le temps moyen du sevrage soit 99,5 4- 5,5 jours. L'auteur sugg6re que la t6t6e et la condition physique agissent comme des r6gulateurs de l'anoestrus post partum pour cette esp6ce. La saison peut 6galement jouer un r61e r6gulateur, &ant donn6 que les ch6vres qui ant mis bas entre avril et juin (n = 6) &aient en anoestrus pendant 82,7 + 15,0 jours, donn6e A comparer ~ 112 + 7,3 jours pour celles qui ant mis bas d'octobre ~ f6vder (n = 6), quoique la diff6rence ne ffit pas significative. CONCENTRACION DE PROGESTERONA EN EL PLASMA DURANTE LA PRENEZ Y PSEUDOPRENEZ E INICIO DE LA ACTIVIDAD OVARICA POS-PARTO EN CABRAS NATIVAS EN ZIMBABWE Resumen---Se, estabularon individualmente ocho cabras prefiadas, d~ndoles heno y concentrados tanto durante la prefiez, coma durante la lactaci6n. El promedio de gestaci6n rue 146.7 + 3'0 dins, con una tasa gemelar de 75 par ciento. La media de condici6n corporal, mejor6 de 2.4 4- 0"2 a 2-8 + 0.2 durante los pdmeros 80 dias de gestaci6n y se mantuvo en 2.8 hasta el din 45 antes del parto, cayendo a 2-2 + 0.2 de ahi en adelante. La concentraci6n de progesterona en el plasma durante la prefiez, subi6 significativamente de 3.91 + 0-51 ng/ml el din 40 a 5.96 + 0"51 ng/ml el dia 60 (P < 0.05), permaneciendo alta hasta 5 dias antes del parto. Tres cabras pseudoprefiadas tuvieron niveles de progesterona similares a aquellos de las cabras prefiadas, durante los primeros 80 dias, pero el aumento alrededor del din 35 a 40 no rue signifieativo y los niveles de progesterona retornaron gradualmente a los niveles basales, despu6s del dia 100. Las mismas 8 cabras, junto con 4 adicionales, que habian sido traidas 60 y 70 dias antes del parto, fueron utilizadas para estudiar el inicio pos-parto de la actividad ov~rica. E1 porcentaje gemetar rue de 83
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LLEWELYN, OGAA AND OBWOLO
por ciento. La condiei6n corporal media al parto fue de 2"2 + 0.1. Para el dia 35 pos-parto, la condici6n corporal media habia ealdo a 1-9 _+ 0.1; los pesos medios de 36.9 + 1.9 al parto, eayeron a 32.1 -I- 2.0 kg. La eielieidad ov~dea se reanud6 un poeo despu~s de que la eondieibn corporal y los pesos mejoraron. El intervalo promedio desde el parto hasta el eomienzo de los ciclosestrales rue de 97.3 + 9.5 dias. Se sugiere que el amamantamiento y la eondiei6n corporal regulan la apariei6n dd estro pos-parto en 6sta espeeie. La estaei6n de pariei6n pueda que juegue un papel importante, debido, a que las eabras que paderon entre abril y junio (n = 6), estuvieron en anestro por 82"7 + 15"0dlas, en eomparaei6n a 112 + 7.3 dlas para las eabras que parieron entre octubre y febrero (n --: 6), aunque la difereneia no fue estadlstieamente significativa.
UNIVERSITY OF EDINBURGH CENTRE FOR TROPICAL VETERINARY MEDICINE Diploma/MSc P O S T G R A D U A T E C O U R S E S The following courses are available: (i) Tropical Veterinary Medicine. This course is designed for field veterinarians aiming at the senior and middle ranks o f veterinary services in developing countries. It deals with the prevention and control of animal diseases at regional and national levels and has a strong epidemiological component. Related aspects of animal production and veterinary public health are also covered. (ii) Tropical Veterinary Science. This is a course for veterinarians, which is mainly concerned with the laboratory diagnosis o f diseases o f animals including poultry and wildlife in developing countries. It also includes the organisation and management o f tropical veterinary laboratories and the epidemiology of the major diseases o f animals. (iii) Tropical Animal Production and Health. This course which is organised in conjunction with the University's Department of Agriculture is open to agriculture and veterinary graduates intending to specialise in animal production in developing countries. It provides a comprehensive review of the main constraints to animal production likely to be encountered in these countries with an indication of how they may be overcome. Further information can be obtained from the Director o f the Centre for Tropical Veterinary Medicine, Easter Bush, Roslin EH25 9RG, Midlothian, Scotland.
