Anon (1987) Victoria Governmetu Gazette, 16 December 1987, p 3430 Corrigan PJ and SeneviratnaP (1990)Aust Vet J 6 7 5 6 Dingle JHP, Palmer WA and Black RR (1989)AustJ Expt Agric 29497 Farmgin AJ (1988)Assessment of PolychlorinatedBiphenyl (PCB) Wastes, State Pollution Control Commission,Sydney Fries GF (1982)JEnviron Qual11:14 Fries GF, Marrow GS and Gordm CH (1973)J Agric Food Chem 21:117 Fuhremann 'IW and Lichtenstein EP (198O)JAgricFood Chem 28446 Gannon N, Link RP and Decker GC (1959)J Agric Food Chem 7:826 Healy WB and Drew KR (1970)NZJAgricRes 8737 Ivey MC, Clayborn HV, Mann HD, Radeleff RD and Woodward GT (1961) J Agric Food Chem9314 Lichtenstein EP, Schulz KR, Fuhremann TW and Liang 'IT (1969)J Econ Entom 62:761 Luke BG, Richards JC and Dawes EF (1984)JAssoc O f A d Chem 67295 McDougall KW (1990)Proc Aust Soc Anim Prod 18 19
Morgan lR (1989) Chemical Residues in Agricultwal Products, Research Report Series No 89. Depament of Agriculture, Melbourne Nash RG (1%8)JAgronomy 60:217 Peny TW. EversonRJ. Hendrix KS, Peterson RC and Robinson FR (1984) J Dairy Sci 67224 Platonow NS. SaschenbreckerPW andFunnellHS (1971)Con VetJl2:llS RichardsonBJ and Waid JS (1979)PCBsin the Port Phillip Region, Ministry for Conservation, Melbourne Safe S. Safe L and Mullin M (1987) In Environmental Toxin Series 1 Polychlorinated Biphenyls (PCBs): Mammalian and Environmental Toxicology,edited by Safe S and Hutzinger 0,Springer-Verlag,Berlin, p 1 SaschenbreckerPW, Funnell HS and Platonow NS (1972) Vet Rec 9O:lOO Sax NI and Lewis RJ (1989)Dangerous Properties of Industrial Materials, 7th edn. VanNostrand Reinland, New York Spence SA. McDougall KW and Deamann EB (1990)Aw Vet J67:383 (Accepted for publication 8 April 1992)
Failure of a single postpartum prostaglandin treatment to improve the reproductive performance of dairy cows JM MORTON*, JD ALLENt' DJ HARRIS' and GT MILLERB SUMMARY: A study was conducted to evaluate the effects of postpartum prostaglandin treatment on reproduction in 3 seasonal calving dairy herds. Recently calved lactating dairy cows were paired on herd, age, calving date and previous production Index. One cow in each of the 196 pairs received a single intramuscular injection of 25 mg of the prostaglandin analogue, dinoprost, between 14 and 28 days after caivlng. Subsequent reproductionwas monitored.Within each herd and overall, there was no significant effect of treatment on the Intervalsfrom calving to first service, mating start date to first service, calving to conception, mating start date to conception and first service to conception. Treatment also had no significant effect on 21-day submission and pregnancy rates, on the proportion of each group not pregnant at the end of mating, and on first service pregnancy rates. Responses to treatment did not vary between cows calving within 50 days of matlngstart date and earlier caivlng cows or betweencows aged lessthan 5 years and older cows. Aust Vet J 69: 158 - 160
Introduction The duration of elevated prostaglandin metabolite levels in plasma in recently calved cows has been inversely associated with time required for complete uterine involution Gindell et a1 1982; Madej et ul1984) and with the interval from parturition to fist ovulation (Madej et ul 1984). However, reproductive responses of cows to exogenous prostaglandin treatments administered between 14 and 40 days postpartum have been variable (Etherington et a1 1984, Young et a1 1984; Benmrad and Stevenson 1986; Young and Anderson 1986; Etherington et a1 1988; Armstrong et ul1989; McClary et a1 1989; Young 1989). Variation in the response to treatment does not appear to be due to the use of different prostaglandin analogues. Positive
responses have been reported following treatment with cloprostenol (Etherington et ul1984, 1988) and dinoprost (Young et ul 1984;Benmrad and Stevenson 1986), while other trials have not detected a significant effect of treatment with dinoprost (Macmillanet a1 1987) and fenprostalene(Armstronget al1989). The response to treatment has also varied in cows with abnormal parturitions (Macmillan et a1 1987; Archbald et al1990, White and Dobson 1990; Glanvill and Dobson 1991). Postpartum prostaglandin treatments may have wick application in seasonal calving dairy herds in Australia if effective in improving fertility. This trial assessed reproductive responses after a single injection of the prostaglandin analogue, dinoprost, administered to cows 14 to 28 days after calving in 3 Victorian dairy herds.
~
Department of Food and Agriculture, 78 Henna Street, Warrnambool, Victoria 3280 Victorian Institute of Animal Science, 475-485 Mickleham Road, Westmeadows, Victoria 3049 Department of Food and Agriculture, 1-3 McCallum Street, Swan Hill, Victoria 3585 8 Department of Food and Agriculture, 70 Smith Street, Warragul, Victoria 3820
*
158
Materials and Methods The trial was conducted in 3 commercial dairy herds, which were selected on the basis of excellent management, accurate cow identification and record keeping, moderately large herd size, availability of herd testing recofds and owner co-operation. Each herd had a seasonal calving pattern and was fed pasture primarily, although supplements of silage and/or hay were fed at
some times of the year in all herds. Herd 1 was located in western Victoria, had a planned start of calving date of 15 July 1986, a herd size of about 340 cows and an annual production level of over 400 kg milkfat per hectare (total annual milkfat production divided by the area available for grazing by lactating cows). A portion of the farm was spray irrigated during summer and autumn. Herds 2 and3 were locatedinwest andcentral Gippsland and had planned start of calving dates of 11July 1986and 10July 1986 respectively, herd sizes of 150 and 134 cows and annual production levels of 460 and 430 kg milkfat per hectare. Neither of these farms practised irrigation. Calving inherd 1was spread over about 14weeks; 95% of cows had calved within 85 days of the planned start of calving. In previous years, herd calving rate to first service had ranged from 44% to 49%, with cows over 4 years having a lower calving rate to first service than younger cows. In herds 2 and 3, calving patterns were more compact; over 95% of cows had calved in the f i t 55 and 65 days respectively, in 1986. Reproductive management in herd 2 was assisted by participation in a herd health program run by a private veterinarian. In each herd, for at least 6 weeks commencing at the start of mating, cows observed in oestrus were artificially inseminated. Bulls were run with all herds for the remainder of the mating period. During calving in 1986 each herd was visited weekly or fortnightly and the calved cows were paired according to age, calving date and average milk production index for all previous lactations. The production index was calculated by the Herd Improvement Organisation of Victoria for each lactation after assessing eachcow's milkfat productionfor the lactation relative to the average production per cow for the herd, with adjustment for age, breed and calving date. Between 14 and 28 days after calving, one cow of each pair received a single intramuscular injection of 25 mg of dinoprostn as the trometamol salt. The other cow in the pair received no treatment. Within each herd, treated and untreated cows were managed as one group throughout the trial. Records of cow identity, age, 1986 calving date, insemination and service dates, 1987 calving date and use of induced calving in 1986and 1987were kept. Conceptiondate was assessedusing service date, the result of manual rectal pregnancy testing performed 7 to 18 weeks after the last service and, for cows that calvedwithoutinductionin 1987, the 1987calvingdate. All cows with neither a record of the subsequent calving date nor a pregnancy test result (and the remaining cow in the respective pair) were excluded from the trial. Binomial variables were analysed using McNemar's chi square test without correctionfor continuity. Continuous variables were analysed by anal sis of variance with blocking for pair and herd using Genstat a statistical analysis package. Analysis of variance was also used to assess interaction between treatment and reproductive responses in early and late calving cows (cows calved more than 50 days or 50 days and less before mating start date) and in young and old cows (cows aged less than 5 years or 5 years and older at 1986calving) for each herd. Calculations of power were performed before the trial using estimated means, standard deviations and proportions. Power for all reproductive intervals and rates was recalculated after the trial using the data and statisticsobserved in the trial assisted by computerpackages (PC-SIZE:Consultant and STPLAN). The power of a trial is the likelihood that the trial will correctly identify a true treatment effect (Martinet a1 1987).
Results The numbers of pairs of cows initially included in the trial in herds 1,2 and 3 were 1 1 8 , s and 41, respectively. Nine pairs in herd 1 and 8 pairs in herd 2 were excluded from the trial when at least one cow in each pair was sold or died before pregnancy testing. There were 109.46 and 41 pairs of cows finally included in the trial in herds 1,2 and 3, respectively. N o significant differences were found between treated and untreated cows for any reproductive variable within each herd and overall. Overall mean values for intervals from calving to first service, mating start date to first service, calving to conception, mating start date to conception and fnst service to conception are shown in Table 1. The proportions of each group that were inseminated at least once during the first 21 days of mating, that conceived during the first 21 days of mating, and that were not pregnant at the end of the mating period are shown in Table 2. The proportions of fsst services that resulted in pregnancy in each group are shown in Table 3. The results were not influenced by age of cows nor by the date of calving relative to the start of mating date. Table 4 shows the differences between treated and untreated groups required for this trial to have had a 0.80 probability of detecting a signifcant difference at the 0.05 level.
TABLE 1 Reproductive performance in cows treated and not treated with prostaglandin 14 to 28 days postpartum Interval
Number of pairs
Mean(days)
Difference
95% confidence intervals for difference'
Not Treated treated Calving to first service
196
71.8
72.0
0.2
3.2, 3 .6
Mating start 196 date to first service
19.8
20.4
0.6
-2.8, 4.0
Calving to conception
17Et
88.5
88.0
-0.5
4.6,5.6
Mating start 17Et date to conception
35.8
36.3
0.5
-6.6,6.6
Firstservice 17Et to conception
16.3
16.8
0.5
-4.4, 5.4
' 95% confidence intervals that include 0 days difference between groups are not significant at the 0.05 level Eighteen pairs of cows were excluded from conception interval analysis when one or both cows in the pair failedto conceiveduring the mating period
3,
TABLE 2 Twentyoneday submission and pregnancy rates and not-incalf rates in cows treated and not treated with prostaglandin14 to 28 days postpartum Rate
Proportion (%) Nottreated Treated
Significance of difference
~~
21day submission rate'
1491196 (76.0) 142/196 (72.4) p00.6
21day pregnancy ratet
88/196 (44.9) 87/196 (44.4)
p=l.O
Not-incalf rate*
101196 (5.1)
p=1.0
111196 (5.6)
~_____
Lawes Agricultural Trust (Rothamsted Experimental Station), Harpenden, Hertfordshire, UK Lutalysee), Upjohn Pty Ltd, Rydalmere, New South Wales Australian veterinary Journal, vol69, No 7, July 1992
*
proportion of group that was inseminated at least once during the first 21 days of mating proportion of group that conceivedduringthe first 21 days of mating proportion of group that was not pregnant at end of mating period
159
Discussion No significant differences were associated with prostaglandin treatment in any of thereproductivei n t e r v a l s andrates examined. 7'hedesignhad sufficient power to detect differencessmallerthan those reported elsewhere (Young et al 19W. Etherington et al 1984, 1988; Benmrad and Stevenson 1986). Differences in all reproductive variables were small and inconsistent between herds. There were no consistent trends in favour of treatment for any variable. Treatment could be profitable in seasonal calving herds in Australia even if it results in only small effects on reproductive performance. However, trials involving much larger numbers of replicates than used in this study are necessary to have a high probability of demonstrating very small differences in reproductive variables. The effect of treatment varies between herds. Macmillan et al (1987) and Young (1989) have suggested that responses to treatment may be much smaller in herds with high fiist service pregnancy rates. Two of the 3 herds in this trial had first service pregnancy rates above the average obtained from a sample of randomly selected Gippsland herds (SJ Hides personal communication) and herds participating in veterinary herd health/reproductive management programs in western Victoria (CD Hibburt personal communication, MC Hamblin personal communication). The fmt service pregnancy rate in herd 1 was lower but was similar to the average obtainedfrom a group of 22 herds from the same district, whosemating records for 1986were subjected to veterinary analysis (CD Hibburt personal
communication). Responses to prostaglandin treatment in herds with lower first service pregnancy rates have not been assessed in this trial. Bonnett et al(1990) reported smaller diameter uterine horns, less vaginal discharge and less endometritis and endometrial fibrosis in cows treated with a Prostaglandin analogue on day 26 postpartum and assessed on day 40 postpartum in a commercial dairy herd. Althoughnot specificallyrecorded in the current trial, a low proportion of cows more than 2 weeks postpartum were detected with abnormal vaginal discharges. Delayed uterine involutionandpostpartumuterineinflammationmaynot have been limitingreproductiveperformancesignificantlyin the trial herds. The interval between calving and treatment may also affect the reproductive responses. Macmillan et a1 (1987) reported a response to treatment in a small group of cows induced to calve prematurely. Treatment was given between 28 and 34 days postpartum. No response was detected in another much larger trial reported in the same paper in which induced cows were treated around day 20. Other reported positive responses (Etherington et al 1984, 1988; Benmrad and Stevenson 1986) were detected incows treated later than 14 to 28 days postpartum, the interval used in this trial. Further research should be directed towards clarifying the effects of treatment on reproductivephysiology and pathology and in assessing responses to treatment in herds with ahigh incidence of postpartum vaginal discharges and with conception rates that are unexpectedly low after all other factors that influence conception rates are taken into account. This may explain the variation in responses to treatment that have been reported and may aid in the selection of herds that are most likely to respond to treatment.
TABLE 3 First service pregnancy rates. In cows treated and not treated wlth prostaglandin 14 to 28 days postpartum In 3 herds
Acknowledgments
1
50/109 (45.9)
50/109 (45.9)
p = 1.0
We would like to acknowledge the assistance andinterest of the 3 participating herd owners, Dr Bill Darmody for providing reproductiverecords and results of reproductiveexaminations in one of the trial herds, and Garry Anderson for assistance with statistical analysis. LutalyseB was kindly provided by Upjohn
2
35146 (76.1)
28/46 (60.9)
p = 0.8
Ply Ltd.
3
25/41 (61.0)
25/41 (61.0)
p = 1.0
110/196 (56.1)
103/196 (52.6)
p = 0.5
Herd
Proportion ("A) Not treated
Total
Treated
Significance of difference
References
21day submission rate ("10)
10.0
21day pregnancy rate (70)
12.0
First service pregnancy rate (YO)
14.0
Amhbald LF, Tran T,Thomas PGA and Lyle SK (1990) Theriogenology 3 4 1025 Amstrong JD,O'Gorman J and Roche JF (1989) Ver Rec 125597 Benmrad M and Stevenson JS (1986) JDuiry Sci 69800 Bonnett BN. Etherington WG, Martin SW and Johnson WH (1990) Theriogenology33:Wl Etherington WG, Bosu WTK, Martin SW, Cote JF,Doig PA and Leslie KE (1984) Can J CompMed 48245 EtheringtonWG,Martin SW, Bonnett B. JohnsonWH,MillerRB er a1 (1988) Theriogenology29565 Glanvill SF and Dobson H (1991) Vet Rec 128374 Lindell J-0, Kindahl H, Jansson L and Edqvist L-E (1982) Theriogenology 17237 M a d a n KL, Day AM, Taufa VK, Henderson HV and Allison PA (1987) Proc Nz Soc A n h Prod 4165 McClary DG, Putnam MR, Wright JC and Sartin JL (1989) Theriogenology 31565 Madej A, Kindahl H. Woyno W, Edqvist L-E and Stupnicki R (1984) Theriogenology21279 Ma& SW, Meek AH and Willeberg P (1987) VeterinuryEpidemiology, Iowa State Universiq Press, Ames. p 181 White AJ and Dobson H (1990) Vet Rec 127588 Young IM.Anderson DB and Plenderleith RWJ (1984) Vet Rec 11S429 Young IM and Anderson DB (1986) Vet Rec 118212 Young IM (1989) Ver Rec 124511
7.0
(Accepted for publication 29 April 1992)
Proportion of first services that resultedin pregnancy,as assessed by manual rectal pregnancy testing and confirmed for most cows with subsequent calving date
TABLE 4 Required dlfferences In reproductive intervals and rates between cows treated and not treated with prostaglandin 14 to 28 days postpartum for 0.80 power of detectlon (wlth a probability of Incorrectly relecting the null hypothesls of 0.05) Reproductive variable
Difference
Calving to first service interval (days)
5.0
Mating start date to first service interval (days)
4.9
Calving to conception interval (days)
8.8
Mating start date to conception interval (days)
8.8
First service to conception interval (days)
7.0
Not-in-calf rate (%)
160
Australian VeterinaryJownal, Vol69, No 7, July 1992
Morgan lR (1989) Chemical Residues in Agricultwal Products, Research Report Series No 89. Depament of Agriculture, Melbourne Nash RG (1%8)JAgronomy 60:217 Peny TW. EversonRJ. Hendrix KS, Peterson RC and Robinson FR (1984) J Dairy Sci 67224 Platonow NS. SaschenbreckerPW andFunnellHS (1971)Con VetJl2:llS RichardsonBJ and Waid JS (1979)PCBsin the Port Phillip Region, Ministry for Conservation, Melbourne Safe S. Safe L and Mullin M (1987) In Environmental Toxin Series 1 Polychlorinated Biphenyls (PCBs): Mammalian and Environmental Toxicology,edited by Safe S and Hutzinger 0,Springer-Verlag,Berlin, p 1 SaschenbreckerPW, Funnell HS and Platonow NS (1972) Vet Rec 9O:lOO Sax NI and Lewis RJ (1989)Dangerous Properties of Industrial Materials, 7th edn. VanNostrand Reinland, New York Spence SA. McDougall KW and Deamann EB (1990)Aw Vet J67:383 (Accepted for publication 8 April 1992)
Failure of a single postpartum prostaglandin treatment to improve the reproductive performance of dairy cows JM MORTON*, JD ALLENt' DJ HARRIS' and GT MILLERB SUMMARY: A study was conducted to evaluate the effects of postpartum prostaglandin treatment on reproduction in 3 seasonal calving dairy herds. Recently calved lactating dairy cows were paired on herd, age, calving date and previous production Index. One cow in each of the 196 pairs received a single intramuscular injection of 25 mg of the prostaglandin analogue, dinoprost, between 14 and 28 days after caivlng. Subsequent reproductionwas monitored.Within each herd and overall, there was no significant effect of treatment on the Intervalsfrom calving to first service, mating start date to first service, calving to conception, mating start date to conception and first service to conception. Treatment also had no significant effect on 21-day submission and pregnancy rates, on the proportion of each group not pregnant at the end of mating, and on first service pregnancy rates. Responses to treatment did not vary between cows calving within 50 days of matlngstart date and earlier caivlng cows or betweencows aged lessthan 5 years and older cows. Aust Vet J 69: 158 - 160
Introduction The duration of elevated prostaglandin metabolite levels in plasma in recently calved cows has been inversely associated with time required for complete uterine involution Gindell et a1 1982; Madej et ul1984) and with the interval from parturition to fist ovulation (Madej et ul 1984). However, reproductive responses of cows to exogenous prostaglandin treatments administered between 14 and 40 days postpartum have been variable (Etherington et a1 1984, Young et a1 1984; Benmrad and Stevenson 1986; Young and Anderson 1986; Etherington et a1 1988; Armstrong et ul1989; McClary et a1 1989; Young 1989). Variation in the response to treatment does not appear to be due to the use of different prostaglandin analogues. Positive
responses have been reported following treatment with cloprostenol (Etherington et ul1984, 1988) and dinoprost (Young et ul 1984;Benmrad and Stevenson 1986), while other trials have not detected a significant effect of treatment with dinoprost (Macmillanet a1 1987) and fenprostalene(Armstronget al1989). The response to treatment has also varied in cows with abnormal parturitions (Macmillan et a1 1987; Archbald et al1990, White and Dobson 1990; Glanvill and Dobson 1991). Postpartum prostaglandin treatments may have wick application in seasonal calving dairy herds in Australia if effective in improving fertility. This trial assessed reproductive responses after a single injection of the prostaglandin analogue, dinoprost, administered to cows 14 to 28 days after calving in 3 Victorian dairy herds.
~
Department of Food and Agriculture, 78 Henna Street, Warrnambool, Victoria 3280 Victorian Institute of Animal Science, 475-485 Mickleham Road, Westmeadows, Victoria 3049 Department of Food and Agriculture, 1-3 McCallum Street, Swan Hill, Victoria 3585 8 Department of Food and Agriculture, 70 Smith Street, Warragul, Victoria 3820
*
158
Materials and Methods The trial was conducted in 3 commercial dairy herds, which were selected on the basis of excellent management, accurate cow identification and record keeping, moderately large herd size, availability of herd testing recofds and owner co-operation. Each herd had a seasonal calving pattern and was fed pasture primarily, although supplements of silage and/or hay were fed at
some times of the year in all herds. Herd 1 was located in western Victoria, had a planned start of calving date of 15 July 1986, a herd size of about 340 cows and an annual production level of over 400 kg milkfat per hectare (total annual milkfat production divided by the area available for grazing by lactating cows). A portion of the farm was spray irrigated during summer and autumn. Herds 2 and3 were locatedinwest andcentral Gippsland and had planned start of calving dates of 11July 1986and 10July 1986 respectively, herd sizes of 150 and 134 cows and annual production levels of 460 and 430 kg milkfat per hectare. Neither of these farms practised irrigation. Calving inherd 1was spread over about 14weeks; 95% of cows had calved within 85 days of the planned start of calving. In previous years, herd calving rate to first service had ranged from 44% to 49%, with cows over 4 years having a lower calving rate to first service than younger cows. In herds 2 and 3, calving patterns were more compact; over 95% of cows had calved in the f i t 55 and 65 days respectively, in 1986. Reproductive management in herd 2 was assisted by participation in a herd health program run by a private veterinarian. In each herd, for at least 6 weeks commencing at the start of mating, cows observed in oestrus were artificially inseminated. Bulls were run with all herds for the remainder of the mating period. During calving in 1986 each herd was visited weekly or fortnightly and the calved cows were paired according to age, calving date and average milk production index for all previous lactations. The production index was calculated by the Herd Improvement Organisation of Victoria for each lactation after assessing eachcow's milkfat productionfor the lactation relative to the average production per cow for the herd, with adjustment for age, breed and calving date. Between 14 and 28 days after calving, one cow of each pair received a single intramuscular injection of 25 mg of dinoprostn as the trometamol salt. The other cow in the pair received no treatment. Within each herd, treated and untreated cows were managed as one group throughout the trial. Records of cow identity, age, 1986 calving date, insemination and service dates, 1987 calving date and use of induced calving in 1986and 1987were kept. Conceptiondate was assessedusing service date, the result of manual rectal pregnancy testing performed 7 to 18 weeks after the last service and, for cows that calvedwithoutinductionin 1987, the 1987calvingdate. All cows with neither a record of the subsequent calving date nor a pregnancy test result (and the remaining cow in the respective pair) were excluded from the trial. Binomial variables were analysed using McNemar's chi square test without correctionfor continuity. Continuous variables were analysed by anal sis of variance with blocking for pair and herd using Genstat a statistical analysis package. Analysis of variance was also used to assess interaction between treatment and reproductive responses in early and late calving cows (cows calved more than 50 days or 50 days and less before mating start date) and in young and old cows (cows aged less than 5 years or 5 years and older at 1986calving) for each herd. Calculations of power were performed before the trial using estimated means, standard deviations and proportions. Power for all reproductive intervals and rates was recalculated after the trial using the data and statisticsobserved in the trial assisted by computerpackages (PC-SIZE:Consultant and STPLAN). The power of a trial is the likelihood that the trial will correctly identify a true treatment effect (Martinet a1 1987).
Results The numbers of pairs of cows initially included in the trial in herds 1,2 and 3 were 1 1 8 , s and 41, respectively. Nine pairs in herd 1 and 8 pairs in herd 2 were excluded from the trial when at least one cow in each pair was sold or died before pregnancy testing. There were 109.46 and 41 pairs of cows finally included in the trial in herds 1,2 and 3, respectively. N o significant differences were found between treated and untreated cows for any reproductive variable within each herd and overall. Overall mean values for intervals from calving to first service, mating start date to first service, calving to conception, mating start date to conception and fnst service to conception are shown in Table 1. The proportions of each group that were inseminated at least once during the first 21 days of mating, that conceived during the first 21 days of mating, and that were not pregnant at the end of the mating period are shown in Table 2. The proportions of fsst services that resulted in pregnancy in each group are shown in Table 3. The results were not influenced by age of cows nor by the date of calving relative to the start of mating date. Table 4 shows the differences between treated and untreated groups required for this trial to have had a 0.80 probability of detecting a signifcant difference at the 0.05 level.
TABLE 1 Reproductive performance in cows treated and not treated with prostaglandin 14 to 28 days postpartum Interval
Number of pairs
Mean(days)
Difference
95% confidence intervals for difference'
Not Treated treated Calving to first service
196
71.8
72.0
0.2
3.2, 3 .6
Mating start 196 date to first service
19.8
20.4
0.6
-2.8, 4.0
Calving to conception
17Et
88.5
88.0
-0.5
4.6,5.6
Mating start 17Et date to conception
35.8
36.3
0.5
-6.6,6.6
Firstservice 17Et to conception
16.3
16.8
0.5
-4.4, 5.4
' 95% confidence intervals that include 0 days difference between groups are not significant at the 0.05 level Eighteen pairs of cows were excluded from conception interval analysis when one or both cows in the pair failedto conceiveduring the mating period
3,
TABLE 2 Twentyoneday submission and pregnancy rates and not-incalf rates in cows treated and not treated with prostaglandin14 to 28 days postpartum Rate
Proportion (%) Nottreated Treated
Significance of difference
~~
21day submission rate'
1491196 (76.0) 142/196 (72.4) p00.6
21day pregnancy ratet
88/196 (44.9) 87/196 (44.4)
p=l.O
Not-incalf rate*
101196 (5.1)
p=1.0
111196 (5.6)
~_____
Lawes Agricultural Trust (Rothamsted Experimental Station), Harpenden, Hertfordshire, UK Lutalysee), Upjohn Pty Ltd, Rydalmere, New South Wales Australian veterinary Journal, vol69, No 7, July 1992
*
proportion of group that was inseminated at least once during the first 21 days of mating proportion of group that conceivedduringthe first 21 days of mating proportion of group that was not pregnant at end of mating period
159
Discussion No significant differences were associated with prostaglandin treatment in any of thereproductivei n t e r v a l s andrates examined. 7'hedesignhad sufficient power to detect differencessmallerthan those reported elsewhere (Young et al 19W. Etherington et al 1984, 1988; Benmrad and Stevenson 1986). Differences in all reproductive variables were small and inconsistent between herds. There were no consistent trends in favour of treatment for any variable. Treatment could be profitable in seasonal calving herds in Australia even if it results in only small effects on reproductive performance. However, trials involving much larger numbers of replicates than used in this study are necessary to have a high probability of demonstrating very small differences in reproductive variables. The effect of treatment varies between herds. Macmillan et al (1987) and Young (1989) have suggested that responses to treatment may be much smaller in herds with high fiist service pregnancy rates. Two of the 3 herds in this trial had first service pregnancy rates above the average obtained from a sample of randomly selected Gippsland herds (SJ Hides personal communication) and herds participating in veterinary herd health/reproductive management programs in western Victoria (CD Hibburt personal communication, MC Hamblin personal communication). The fmt service pregnancy rate in herd 1 was lower but was similar to the average obtainedfrom a group of 22 herds from the same district, whosemating records for 1986were subjected to veterinary analysis (CD Hibburt personal
communication). Responses to prostaglandin treatment in herds with lower first service pregnancy rates have not been assessed in this trial. Bonnett et al(1990) reported smaller diameter uterine horns, less vaginal discharge and less endometritis and endometrial fibrosis in cows treated with a Prostaglandin analogue on day 26 postpartum and assessed on day 40 postpartum in a commercial dairy herd. Althoughnot specificallyrecorded in the current trial, a low proportion of cows more than 2 weeks postpartum were detected with abnormal vaginal discharges. Delayed uterine involutionandpostpartumuterineinflammationmaynot have been limitingreproductiveperformancesignificantlyin the trial herds. The interval between calving and treatment may also affect the reproductive responses. Macmillan et a1 (1987) reported a response to treatment in a small group of cows induced to calve prematurely. Treatment was given between 28 and 34 days postpartum. No response was detected in another much larger trial reported in the same paper in which induced cows were treated around day 20. Other reported positive responses (Etherington et al 1984, 1988; Benmrad and Stevenson 1986) were detected incows treated later than 14 to 28 days postpartum, the interval used in this trial. Further research should be directed towards clarifying the effects of treatment on reproductivephysiology and pathology and in assessing responses to treatment in herds with ahigh incidence of postpartum vaginal discharges and with conception rates that are unexpectedly low after all other factors that influence conception rates are taken into account. This may explain the variation in responses to treatment that have been reported and may aid in the selection of herds that are most likely to respond to treatment.
TABLE 3 First service pregnancy rates. In cows treated and not treated wlth prostaglandin 14 to 28 days postpartum In 3 herds
Acknowledgments
1
50/109 (45.9)
50/109 (45.9)
p = 1.0
We would like to acknowledge the assistance andinterest of the 3 participating herd owners, Dr Bill Darmody for providing reproductiverecords and results of reproductiveexaminations in one of the trial herds, and Garry Anderson for assistance with statistical analysis. LutalyseB was kindly provided by Upjohn
2
35146 (76.1)
28/46 (60.9)
p = 0.8
Ply Ltd.
3
25/41 (61.0)
25/41 (61.0)
p = 1.0
110/196 (56.1)
103/196 (52.6)
p = 0.5
Herd
Proportion ("A) Not treated
Total
Treated
Significance of difference
References
21day submission rate ("10)
10.0
21day pregnancy rate (70)
12.0
First service pregnancy rate (YO)
14.0
Amhbald LF, Tran T,Thomas PGA and Lyle SK (1990) Theriogenology 3 4 1025 Amstrong JD,O'Gorman J and Roche JF (1989) Ver Rec 125597 Benmrad M and Stevenson JS (1986) JDuiry Sci 69800 Bonnett BN. Etherington WG, Martin SW and Johnson WH (1990) Theriogenology33:Wl Etherington WG, Bosu WTK, Martin SW, Cote JF,Doig PA and Leslie KE (1984) Can J CompMed 48245 EtheringtonWG,Martin SW, Bonnett B. JohnsonWH,MillerRB er a1 (1988) Theriogenology29565 Glanvill SF and Dobson H (1991) Vet Rec 128374 Lindell J-0, Kindahl H, Jansson L and Edqvist L-E (1982) Theriogenology 17237 M a d a n KL, Day AM, Taufa VK, Henderson HV and Allison PA (1987) Proc Nz Soc A n h Prod 4165 McClary DG, Putnam MR, Wright JC and Sartin JL (1989) Theriogenology 31565 Madej A, Kindahl H. Woyno W, Edqvist L-E and Stupnicki R (1984) Theriogenology21279 Ma& SW, Meek AH and Willeberg P (1987) VeterinuryEpidemiology, Iowa State Universiq Press, Ames. p 181 White AJ and Dobson H (1990) Vet Rec 127588 Young IM.Anderson DB and Plenderleith RWJ (1984) Vet Rec 11S429 Young IM and Anderson DB (1986) Vet Rec 118212 Young IM (1989) Ver Rec 124511
7.0
(Accepted for publication 29 April 1992)
Proportion of first services that resultedin pregnancy,as assessed by manual rectal pregnancy testing and confirmed for most cows with subsequent calving date
TABLE 4 Required dlfferences In reproductive intervals and rates between cows treated and not treated with prostaglandin 14 to 28 days postpartum for 0.80 power of detectlon (wlth a probability of Incorrectly relecting the null hypothesls of 0.05) Reproductive variable
Difference
Calving to first service interval (days)
5.0
Mating start date to first service interval (days)
4.9
Calving to conception interval (days)
8.8
Mating start date to conception interval (days)
8.8
First service to conception interval (days)
7.0
Not-in-calf rate (%)
160
Australian VeterinaryJownal, Vol69, No 7, July 1992
