First Postpartum Luteal Function In Dairy Cows After Ovulation Induced by Progestogen and Gonadotropin-Releasing Honnone1 MICHAEL O. MEE, JEFFREY S. STEVENSON,2 and J. ERNEST MINTON Department of Animal SCiences and Iniffercot from progestogen-treated cows (P < .OS). from progestogen-treated cows (P < .10). lCows were implanted with a blank or 6 mg of oorgestomet for 6 do begiDDi.Dg 2 to S d postpartum. Cows
boiffercnt SO
~
were
given
of GnRH 72 h after implant removal.
tions of PGFM were lower (P < .05) in cows previously treated with progestogen implants (578 ± 21 pg/mI) than in control cows (753 ± 21 pg/ml) (Figure 4). Response to GnRH·lnduced Ovulation and Luteal Function
Apparently 43 of 55 cows ovulated after GnRH because they had elevated concentrations of progesterone in serum 3 to 5 d after GnRH injection. All cows that failed to ovulate in response to GnRH (no rise in progesterone in serum within 3 to 5 d after injection) spontaneouslyovulated 10 to 20 d later. The proportion of cows that responded to GnRH tended (P = .12) to be higher after progestogen (24 of 28) than after blank (19 of 27) implants (FIgure 5). A greater (P < .10) proportion of control cows that received blank implants had short luteal phases (3 to 10 d in duration; 7 of 19) than those given progestogen implants (3 of 22). Similarly, more cows (P < .05) that ovulated in response to GnRH had short luteal phases than cows that failed to respond to GnRH (10 of 31 vs. 0 of 10; Figure 5). Intervals to first ovulation after GnRH and duration of the first luteal phase are summaJournal of Dairy Science Vol 74, No. S, 1991
rized in Table 2. Fourteen cows with extended luteal phases (Figure 5) were excluded from this analysis because their first luteal phase was associated with possible uterine pathology, resulting in retained CL. The interval to first ovulation occurred earlier (by definition) in cows that responded to GnRH (3.8 ± .5 d) than in those failing to respond (20.2 ± .9 d). In addition, there was an effect of lactation number with days to first ovulation occurring earlier (P < .Ol) after GnRH injection for primiparous than multiparous cows (4.8 ± 1.2 versus 9.4 ± 1.2 d, respectively). The duration of the first luteal phase in control cows with elevated concentrations of progesterone in serum 3 to 5 dafter GnRH injection was shorter (P < .10) than that of cows receiving progestogen but with elevated progesterone after GnRH (10.2 ±.9 versus 13.2 ± .8 d). In fact, normal luteal phases (12 to 16 d) were observed in cows failing to have elevated progesterone after GnRH whether or not they were previously treated with progestogen (14.5 ± 1.7 and 14.6 ± 1.4 d, respectively). Primiparous control cows had shorter first luteal phases (12.0 ± 1.5 d) than did multiparous control cows (17.2 ± 1.5 d) or primiparous cows receiving progestogen implants (15.6 ± 1.5 d).
1577
FlRST POSlPARnJM LUTEAL FUNCTION
Serum LH and FSH after Removal of Implants 3
3
LH (ng/ml)
Blank --+-
LH (ng/ml)
(n-8)
Blank --+- Progestogen (n·8)
Progestogen (n·8)
2
2
o
-----.--------,----,-.~,-~~~
o
2
4
6
24 to 30 h
'I
8
10
12
14
18
18 20 22 24
66 to 72 h 3
FSH (ng/mll
Blank
FSH (ng/ml)
(n-8)
--+- Progestogen (n·8)
Blank
(n·8)
Progestogen (n-8)
2
21 1
o~~~~~-~~-,-~~-~~~
024
88m
~
~
w w
~
~
M
15-min Intervals
o
--.--r-------.---,-~~~-
o
2
4
8
8
10
12
14
16
18 20 22 24
15-min Intervals
Figure 1. Concentrations of PSH (USDA-PSH-BP3) BDd LH (USDA-bLH-I-l) in serum of dairy cows from 24 to 30 h BDd 66 to 72 h after implant removal. Concentrations represent an average of eight cows per group [progestogen (+) versus blank implant (.»). Cows were implanted previonsly with either 6 mg of progcstogen (IlOIgcstomet) or a blank implant (control) for 6 Ii, beginning 2 to 5 d postpartum.
DISCUSSION
This study demonstrated that progestogen treatment for 6 d before a GnRH injection reduced the proportion of short luteal phases in periparturient milked cows that had elevated concentrations of progesterone in serum 3 to 5 dafter GnRH injection. Our findings agree with previous work with suckled beef cows when progestogen treatment (administered at much later postpartum intervals), begun either at weaning (18, 19) or prior to a gonadotropininduced ovulation (6, 7), decreased the proportion of cows determined to have a short luteal phase. Garcia-Winder et al. (6, 7) observed that treatment with progestogen enhanced the lifespan of the induced CL by increasing the frequency of LH pulses during progestogen
treatment and thereby influencing maturation of ovarian follicles. In our study, as well as in others (8, 19), an increase in frequency of LH was not observed; however, our period of blood collection occurred after removal of the progestogen implant and not during progestogen treatment. In other studies, progestogen treatment failed to alter pre- or postovulatory gonadotropin concentrations, which led those authors to conclude that occurrence of short luteal phases was probably not a result of inadequate gonadotropin stimulation (3, 8). A recent report provided evidence that low level physiological concentrations of progesterone administered by a progesterone-releasing intravaginal device increased pulse frequency of LH in cows during the estrous cycle (20). In Journal of Dairy SCience Vol. 74, No.5, 1991
1578
MEE ET AL.
TABLE 2. Luteal function in dairy cows: response 10 progestogen implants and GnRH. 1 Implant treatment Item
Progestogen
Progestogen
Control
Control
GnRH-induced ovulation2 Number of cowSJ
Yes 18
No 4
Yes 13
No 6
X Days to first ovulationa Duration of first luteal phase,b d
X
SE
3.8 13.2
.4 .8
X
SE 1.1 1.7
20.0 14.5
3.7 10.2
SE
X
SE
.5
20.3 14.6
.8 1.4
.9
&QnRH effect (P < .05).
~gestogen by GnRH interaction (P < .10). 1All cows were treated with 6 mg of progestogen or a blank implant (control) for 6 d beginning 2 to 5 d postpartum. 2All cows were administered 50 J18 of GnRH 72 h after implant removal. Cows were assumed 10 have responded 10 GnRH if progesterone in serum was greater than .5 ngIml for 3 consecutive d within 3 10 5 d after GnRH administration. ~cludes cows with abnonnally long luteal phases (>16 d).
our study, the magnitude of LH release after GnRH injection was greater in cows pretreated with progestogen. Results observed in anestrous beef cows were similar (25). Because ovarian follicles of milked cows respond to LH pulses by secreting pulses of estradiol early postpartum (17), progestogen-induced pulses of LH possibly induced higher concentrations of estradiol, which further enhanced the ability of GnRH to release LH after GnRH injection.
Other research has shown that short luteal phases may be due, in part, to altered follicular development (1, 10, 11), which might lead to the premature release of uterine PGFza observed in suckled or nonsuckled cows with first short luteal phases (2, 3, 33). These alterations in follicular function are observed in cows expected to have a short luteal phase in which their follicular cells had fewer receptors for LH and FSH and lower follicular concentrations of estradiol than corresponding follicles examined
Serum Concentrations of LH and FSH B-i-ng~/m:.:..:.:..-1
-----, Blank
6
. ~
pg/ml
(n-B)
18-r-=-------------------,
-+- Progutogen (n-B)
6
3
Serum Concentrations of Estradiol
LH
7
ant-~
1m
14 12 10
r".-... . . . .~--~~~"='h"'"""""J
0+----,---,----.----.--------.---'
o
1
2
3
..
6
8
Hours after 50 J.l.Q GnRH
8 8
4
2 O-'---,---.----.--,----r-----,,---r-----.-~_.---'
~
Figure 2. Concentrations of FSH (USDA-FSH-BP3) and LH (USDA-bLH-I-l) in serum of dairy cows after 50 J18 GnRH given 72 h after implant removal. CoDCeDtrations represent an average of eight cows pa' group [progestogen (+) vs. blank implant (.)]. Cows were implanted previously with either 6 mg of progestogen (norgestotnet) or a blank implant (control) for 6 d, beginDiDg 2 10 5 d postpartum. Standard errors for concentrations of FSH were ± .2 ngIml and for concentrations of LH were ± oS ngIml. Journal of Dairy Science Vol. 74, No.5, 1991
4
~
~
~
~
~
~
0
1
2
3
Days from GnRH Injection Figure 3. Concentrations of estradiol-17~ in serum of dairy cows collected from the beginning of the implant period until 3 d after a 5O-J18 injection of GnRH. Cows
were implanted with 6 mg of progestogen (norgestomet) or a blank implant (control) for 6 d, beginning 2 10 5 d postpartum. Standard errors for average concentrations of estradiol-17~ were ± 1.7 pgIml.
1579
FIRST POSTPARTIJM LUTEAL FUNCTION
Duration of Luteal Phases
Serum Concentrations of PGFM
18 Frequency
pg/ml 2600. -~.. ~
Imj:l1llnJ.J
2000 1600
18
Blank
---+-- Progeatogen
12
_
~
10
_
8
1000
16
14
12-:-1
Short
(e
Normal
(12-18 d)
I
Extended (> 18 d) 7
6 4 2
600 0.L--,--~~~-,--~--.---,---.----r--.---r--,.---.J
-8 -6 -4 -2 0 2 4 6 8 10 12 14 16 16 20
Days from GnRH Injection Figure 4. Concentrations of 13,14-dihydro, 15-ketoprostaglandin F2o: (PGFM) collected from the beginning of the implant period until 20 d after 50 J.1g of GnRH. Cows were implanted with 6 mg of progestogen (norgestomet) or a blank implant (control) for 6 d, beginning 2 to 5 d postpartum. Standard errors for average concentrations of PGFM were ± 20 pg/mJ.
in nonnally cycling COWS (1). Inskeep et al. (10) also observed that follicles from progestogen-treated cows had increased receptors for LH in both granulosa! and thecal cells and higher estradiol concentrations in follicular fluid than corresponding follicles of control cows. Furthennore, progestogen treatment of suckled cows for 9 d altered maturation of the largest follicle, which produced more estradiol and established the dominance of a single follicle (7). In addition, Day et aI. (4) reported that the incidence of short luteal phases was lower in cows receiving an estradiol-17(3 implant from 2 to 40 d postpartum than in untreated controls. Hysterectomy prevented regression of the CL in cycling ewes (11), anestrous ewes (26), and postpartum suckled cows (3) anticipated to have a short luteal lifespan, and luteal lifespan was prolonged with uterine administration of indomethacin in suckled cows induced to ovulate with GnRH (29). We observed prolonged luteal function after the GnRH-induced first ovulation in 12 of our periparturient milked cows with suspected uterine pathology. Active immunization of anestrous beef cows against PGF2a also extended the lifespan of CL anticipated to be short-lived (3). Thus, shortlived CL do not have an inherently short lifespan (2, 3, 11, 26, 29) because the uterus plays an important role in determining the
o
*-Yea Yea-No No-Yea No-No Progestogen - GnRH Response
Figure 5. Frequency of either short, normal, or extended luteal phases in response to treatment with 6 mg of progestogen or a blank implant (control) for 6 d, beginning 2 to 5 d postpartum. The GnRH (SO J.1g) was injected (i.III.) 72 h after removal of implants.
lifespan of the first postpartum CL, Prostaglandin F2a. which is secreted from the uterus, is considered to be the major luteolysin responsible for demise of the CL of the short luteal phase (2, 3, 33). The early demise of the CL induced by premature release of PGF2a might be associated, in part, with deficiencies in the preovulatory follicle that formed the CL of the short luteal phase (1, 10, 11). Recently, CL anticipated to be short-lived were not observed to be more responsive to PGF2a than CL anticipated to have a nonnal lifespan (2). This finding is consistent with the fact that although most of the receptors for PGF2a are found in large luteal cells of the CL (5), there was no difference observed in the properties of large and small luteal cells in short-lived compared with nonnal CL (21). Furthermore, Zollers et aI. (33) reported that oxytocin induced a release of PGF2a on d 5 (d o = estrus) in cows anticipated to have shortlived CL but not in cows pretreated with progestogen that had nonnal luteal phases. They aIso reported that the oxytocin-induced release of PGF2a on d 5 was similar to oxytocin-induced release of PGF2a on d 16 of a nonnaI estrous cycle. It is not known how progestogen treatment affects oxytocin release or what its relationship is to the subsequently lower concentrations of PGF2a. In our study. concentrations of PGFM were lower for 12 d Journal of Dairy Science Vol. 74, No.5, 1991
1580
MEE BT AL.
after GnRH injection in progestogen-treated cows, which substantiated the belief of Troxel and Kesler (30) that the mechanism associated with progestogen treatment involved a reduction in PGF2a secretion mediated by the ovary rather than by the pituitary. Perhaps the higher concentrations of serum estradiol observed in progestogen-treated cows induced uterine progesterone receptors as reported in sheep (32), and when bound to its receptor, progestogen interferes with the induction of oxytocin receptors (13). H this is true, the overall result would be reduced secretion of PGF2a and less probability of a short luteal phase. CONCLUSION
This study provides evidence that pretreatment with progestogen before a GnRH-induced ovulation reduced the incidence of short luteal phases in postpartum milked cows, even when treatment began as early as 2 to 5 d postpartum. These findings and others (6, 7, 10, 11, 18) indicated that pretreatment with progestogen enhances the lifespan and function of the first CL formed after ovulation. However, our progestogen treatment was not as effective in preventing short luteal phases as in earlier studies, perhaps due to a shorter duration of treatment (6 d), beginning much sooner postpartum than in earlier studies. In our study, periparturient milked cows exposed to progestogen before GnRH injection had increased concentrations of estradiol and UI after GnRH and lower concentrations of PGFM in serum, resulting in fewer short luteal phases. It appeared that progestogen had a priming effect on hypothalamic-pituitary function, resulting in increased LH release followed by increased secretion of estradiol by preovulatory follicles that was associated with prolonged postovulatory luteal function relative to controls. ACKNOWLEDGMENTS
We express appreciation to Tammi DelCurto, Karla Parsons, and Betty Hensley for their assistance in the laboratory; to SANOFI Animal Health, Overland Parle, KS for donation of the norgestomet and blank implants; and to Brenda Diederich and Val Stillwell for typing this manuscript. We thank K. Kirton, The Upjohn Company, Kalamazoo, MI for donating Journal of Dairy Science Vol. 74, No.5, 1991
the antiserum to 13,I4-dihydro-15-keto-prostaglandin F2a, Norman Mason, Eli Lilly and Company, Indianapolis, IN for donating the estradiol antiserum; and Doug Bolt, USDAARS, Beltsville, MD, and the Hormone Distribution Office, National Institute of Diabetes and Digestive and Kidney Diseases, Bethesda. MD for donating the pituitary hormone preparations. REFERENCES
1 Braden, T. D., M. E. King, K. G. Odde, and G. D. Niswender. 1989. Development of preovulatory follicles expected to form short-lived corpora lutea in beef cow. J. Reprod. FertiI. 85:97. 2 Copelin, J. P., M. F. Smith, D. H. Keisler, and H. A. Garverick. 1989. Effect of active immunization of prepartum and post-partum cows against prostaglandin F2a on lifespan and progesterone secretion of shortlived corpora lutea. J. Reprod. Fertil. 87: 199. 3 Copelin, J. P., M. F. Smith, and R. S. Youngquist 1987. Effect of the uterus on subnormal luteal function in anestrous beef cows. J. Anim. Sci. 64: 1506. 4 Day, M. L., R. M. Dyer, G. W. Wilson, and W. F. Pope. 1990. Influence of estradiol on duration of anestrus and incidence of short estrus cycles in postpartum cows. Domest Anim. Endocrinol. 7:19. 5 Fritz, T. A., M. H. Mayan, H. R. Sawyer, and G. D. N.iswcDder. 1982. Characterization of two steroidogeDic cell types in ovine corpus luteum. BioI. Reprod.
'1:1:703. 6 Garcia-Winder, M., P. B. Lewis, D. R. Deaver. V. G. Smith, G. S. Lewis, and E. K. Inskeep. 1986. Endocrine profiles associated with lifespan of induced corpora lutea in postpartum beef cows. J. Anim. Sci. 62:
1353. 7 Garcia-Winder, M., P. B. Lewis, E. C. Townsend, and E. K. Inskeep. 1987. Effects of norgestomet on follicular development in postpartum beef cows. J. Anim. Sci 64:1099. 8 Garverick, H. A., J. R. Parfet, C. N. Lee, J. P. Copelin, R. S. Youngquist, and M. F. Smith. 1988. Relationship of pre- and post-ovuIatory gonadotropin concentrations to suboorma11uteal function in postpartum beef cattle. J. Anim. Sci. 66:104. 9 Garverick, H. A., IIIJd M. F. Smith. 1986. Mechanism 8I8OCiated with suboorma1 luteal function. J. Anim. Sci. 62(Suppl. 2):92. 10 Inskeep, E. K., T. D. Braden, P. B. Lewis, M. GarciaWinder, and G. D. Niswender. 1988. Receptors for luteinizing hormone and follicle-stimulating hormone in 1argest follicles of postpartum beef cows. BioI. Reprod. 38:587. 11 Keisler, D. H., IIIJd L. W. Keisler. 1989. Formation and function of GnRH-induced subnormal corpora lutea in cyclic ewes. J. Reprod. Fertil. 87:265. 12 Marion, G. B., and H. T. Gier. 1986. FactoIS affecting bovine ovarian activity after parturition. J. Anim. Sci. 27:1621.
13 McCracken, J. A, W. Schramm, and W. C. Oku1icz.
FIRST POSTPARlUM LUTEAL FUNCTION 1984. Hormone receptor control of pulsatile secretion of PGF2a. from the ovine uterus during luteolysis and its abrogation in early pregnancy. Anim. Reprod. Sci. 7:31. 14 National ReseaJCh Council. 1978. Nutrient requirements of dairy cattle. Natl. Acad. Sci., Washington, DC. 15 Newton, E. A, J. S. Stevenson, J. E. Minton, and D. L. Davis. 1987. Endocrine changes before and after weaning in response to boar exposure and altered suckling in sows. J. Reprod. Fer1il. 81:599. 16 Odde, K. G., H. S. Ward, G. H. Kiracofe, R. M. McKee, and R. J. Kittok. 1980. Short estrous cycles and associated serum progesterone levels in beef cows. Theriogenology 14:105. 17 Peters, A. R., and BM.A.O. Perera. 1989. Pulsatile secretion of oestradiol-1713 in post-partwn dairy cows. Anim. Prod. 49:335. 18 Ramirez-Godinez, J. A., G. H. Kiracofe, R. M McKee, R. R. Schalles, and R. J. Kittok. 1981. Reducing the incidence of short estrous cycles in beef cows with norgestomet. Theriogenology 15:613. 19 Ramirez-Godinez, J. A., G. H. Kiracofe, R. R. Schalles, and G. D. Niswender. 1982. Endocrine patterns in the postpartum beef cow associated with weaning. A comparison of the short and subsequent normal cycles. J. AninI. Sci. 55:153. 20 Roberson, MS., M. W. Wolfe, T. T. Stumpf, R. J. Kittok, and J. E. Kinder. 1989. Luteinizing hormone secretion and corpus luleum function in cows receiving two levels of progesterone. BioI. Reprod. 41:991. 21 Rutter, L. M, T. D. Carruthers, and J. G. Manns. 1985. The postpartum induced corpus luteum: functional differences from that of cycling cows and the effects of progesterone pretreatment. BioI. Reprod. 33:560. 22 SAS$ User's Guide: Statistics, Version 5 Edition. 1982. SAS Inst., Inc., Cary, NC. 23 Skaggs, C. L., B. V. Able, and J. S. Stevenson. 1986. Pulsatile or continuous infusion of luteinizing hormone-releasing hormone and hormonal concentrations in prepubertal beef heifers. J. Anim. Sci. 62:1034.
1581
24 Smith, M F. 1986. Recent advances in corpus luteum physiology. J. Dairy Sci. 69:911. 25 Smith, M. F., A. W. Lishman, G. S. Lewis, P. G. Harms, M R. Ellersieck, E. K. Inskeep, J. N. Wiltbank, and M S. Amos. 1983. Pituitary and ovarian responses to gonadotropin-releasing hormone, calf removal and progestogen in anestrus beef cows. J. AninI. Sci. 57:418. 26 Soulhee, J. A., M G. Hunter, A. S. Law, and W. Haresign. 1988. Effect of hysterectomy on the short life-cycle corpus luteum produced after GnRH-induced ovulation in the anestrous ewe. J. Reprod. Fertil. 84: 149. 27 Stevenson, J. S., and E. P. Call. 1983. Influence of early estIus, ovulation, and insemination on fertility in postpartum Holstein cows. Theriogenology 19:367. 28 Stewart, R. E., and J. S. Stevenson. 1987. Hormonal, estrual, ovulatory and milk traits in postpartum dairy cows following multiple daily injections of oxytocin. J. Anim. Sci 65:1585. 29 Troxel, T. R., and D. J. Kesler. 1984. Ability of indomethacin to alter prostaglandin metabolite concentrations and to enhance the function of corpora lutea induced in postpartum suckled beef cows. J. Anim. Sci. 59:177. 30 Troxel, T. R., and D. J. Kesler. 1984. The effect of progestin and GnRH treatments on ovarian function and reproductive hormone secretions of anestrous postpartum suckled beef cow. Theriogenology 21:699. 31 Wettemann, R. P. 1980. Postpartum endocrine function of cattle, sheep, and swine. J. Anim. Sci. 51(Suppl. 2):
2. 32 Zelinski, M B., N. A. Hirota, E. J. Keenan, and F. Stormshak. 1980. Influence of exogenous estradiol-17/i on endometrial progesterone and estrogen receptors during the luteal phase of the ovine estrous cycle. BioI. Reprod. 23:743. 33 Zollers, Jr., W. G., H. A. Garverick, aud M. F. Smith. 1989. Oxytocin-induced release of prostaglandin F2a. in postpartum beef cows: comparison of short versus normal luteal phases. BioI. Reprod. 41:262.
Journal of Dairy Science Vol. 74, No.5, 1991
boiffercnt SO
~
were
given
of GnRH 72 h after implant removal.
tions of PGFM were lower (P < .05) in cows previously treated with progestogen implants (578 ± 21 pg/mI) than in control cows (753 ± 21 pg/ml) (Figure 4). Response to GnRH·lnduced Ovulation and Luteal Function
Apparently 43 of 55 cows ovulated after GnRH because they had elevated concentrations of progesterone in serum 3 to 5 d after GnRH injection. All cows that failed to ovulate in response to GnRH (no rise in progesterone in serum within 3 to 5 d after injection) spontaneouslyovulated 10 to 20 d later. The proportion of cows that responded to GnRH tended (P = .12) to be higher after progestogen (24 of 28) than after blank (19 of 27) implants (FIgure 5). A greater (P < .10) proportion of control cows that received blank implants had short luteal phases (3 to 10 d in duration; 7 of 19) than those given progestogen implants (3 of 22). Similarly, more cows (P < .05) that ovulated in response to GnRH had short luteal phases than cows that failed to respond to GnRH (10 of 31 vs. 0 of 10; Figure 5). Intervals to first ovulation after GnRH and duration of the first luteal phase are summaJournal of Dairy Science Vol 74, No. S, 1991
rized in Table 2. Fourteen cows with extended luteal phases (Figure 5) were excluded from this analysis because their first luteal phase was associated with possible uterine pathology, resulting in retained CL. The interval to first ovulation occurred earlier (by definition) in cows that responded to GnRH (3.8 ± .5 d) than in those failing to respond (20.2 ± .9 d). In addition, there was an effect of lactation number with days to first ovulation occurring earlier (P < .Ol) after GnRH injection for primiparous than multiparous cows (4.8 ± 1.2 versus 9.4 ± 1.2 d, respectively). The duration of the first luteal phase in control cows with elevated concentrations of progesterone in serum 3 to 5 dafter GnRH injection was shorter (P < .10) than that of cows receiving progestogen but with elevated progesterone after GnRH (10.2 ±.9 versus 13.2 ± .8 d). In fact, normal luteal phases (12 to 16 d) were observed in cows failing to have elevated progesterone after GnRH whether or not they were previously treated with progestogen (14.5 ± 1.7 and 14.6 ± 1.4 d, respectively). Primiparous control cows had shorter first luteal phases (12.0 ± 1.5 d) than did multiparous control cows (17.2 ± 1.5 d) or primiparous cows receiving progestogen implants (15.6 ± 1.5 d).
1577
FlRST POSlPARnJM LUTEAL FUNCTION
Serum LH and FSH after Removal of Implants 3
3
LH (ng/ml)
Blank --+-
LH (ng/ml)
(n-8)
Blank --+- Progestogen (n·8)
Progestogen (n·8)
2
2
o
-----.--------,----,-.~,-~~~
o
2
4
6
24 to 30 h
'I
8
10
12
14
18
18 20 22 24
66 to 72 h 3
FSH (ng/mll
Blank
FSH (ng/ml)
(n-8)
--+- Progestogen (n·8)
Blank
(n·8)
Progestogen (n-8)
2
21 1
o~~~~~-~~-,-~~-~~~
024
88m
~
~
w w
~
~
M
15-min Intervals
o
--.--r-------.---,-~~~-
o
2
4
8
8
10
12
14
16
18 20 22 24
15-min Intervals
Figure 1. Concentrations of PSH (USDA-PSH-BP3) BDd LH (USDA-bLH-I-l) in serum of dairy cows from 24 to 30 h BDd 66 to 72 h after implant removal. Concentrations represent an average of eight cows per group [progestogen (+) versus blank implant (.»). Cows were implanted previonsly with either 6 mg of progcstogen (IlOIgcstomet) or a blank implant (control) for 6 Ii, beginning 2 to 5 d postpartum.
DISCUSSION
This study demonstrated that progestogen treatment for 6 d before a GnRH injection reduced the proportion of short luteal phases in periparturient milked cows that had elevated concentrations of progesterone in serum 3 to 5 dafter GnRH injection. Our findings agree with previous work with suckled beef cows when progestogen treatment (administered at much later postpartum intervals), begun either at weaning (18, 19) or prior to a gonadotropininduced ovulation (6, 7), decreased the proportion of cows determined to have a short luteal phase. Garcia-Winder et al. (6, 7) observed that treatment with progestogen enhanced the lifespan of the induced CL by increasing the frequency of LH pulses during progestogen
treatment and thereby influencing maturation of ovarian follicles. In our study, as well as in others (8, 19), an increase in frequency of LH was not observed; however, our period of blood collection occurred after removal of the progestogen implant and not during progestogen treatment. In other studies, progestogen treatment failed to alter pre- or postovulatory gonadotropin concentrations, which led those authors to conclude that occurrence of short luteal phases was probably not a result of inadequate gonadotropin stimulation (3, 8). A recent report provided evidence that low level physiological concentrations of progesterone administered by a progesterone-releasing intravaginal device increased pulse frequency of LH in cows during the estrous cycle (20). In Journal of Dairy SCience Vol. 74, No.5, 1991
1578
MEE ET AL.
TABLE 2. Luteal function in dairy cows: response 10 progestogen implants and GnRH. 1 Implant treatment Item
Progestogen
Progestogen
Control
Control
GnRH-induced ovulation2 Number of cowSJ
Yes 18
No 4
Yes 13
No 6
X Days to first ovulationa Duration of first luteal phase,b d
X
SE
3.8 13.2
.4 .8
X
SE 1.1 1.7
20.0 14.5
3.7 10.2
SE
X
SE
.5
20.3 14.6
.8 1.4
.9
&QnRH effect (P < .05).
~gestogen by GnRH interaction (P < .10). 1All cows were treated with 6 mg of progestogen or a blank implant (control) for 6 d beginning 2 to 5 d postpartum. 2All cows were administered 50 J18 of GnRH 72 h after implant removal. Cows were assumed 10 have responded 10 GnRH if progesterone in serum was greater than .5 ngIml for 3 consecutive d within 3 10 5 d after GnRH administration. ~cludes cows with abnonnally long luteal phases (>16 d).
our study, the magnitude of LH release after GnRH injection was greater in cows pretreated with progestogen. Results observed in anestrous beef cows were similar (25). Because ovarian follicles of milked cows respond to LH pulses by secreting pulses of estradiol early postpartum (17), progestogen-induced pulses of LH possibly induced higher concentrations of estradiol, which further enhanced the ability of GnRH to release LH after GnRH injection.
Other research has shown that short luteal phases may be due, in part, to altered follicular development (1, 10, 11), which might lead to the premature release of uterine PGFza observed in suckled or nonsuckled cows with first short luteal phases (2, 3, 33). These alterations in follicular function are observed in cows expected to have a short luteal phase in which their follicular cells had fewer receptors for LH and FSH and lower follicular concentrations of estradiol than corresponding follicles examined
Serum Concentrations of LH and FSH B-i-ng~/m:.:..:.:..-1
-----, Blank
6
. ~
pg/ml
(n-B)
18-r-=-------------------,
-+- Progutogen (n-B)
6
3
Serum Concentrations of Estradiol
LH
7
ant-~
1m
14 12 10
r".-... . . . .~--~~~"='h"'"""""J
0+----,---,----.----.--------.---'
o
1
2
3
..
6
8
Hours after 50 J.l.Q GnRH
8 8
4
2 O-'---,---.----.--,----r-----,,---r-----.-~_.---'
~
Figure 2. Concentrations of FSH (USDA-FSH-BP3) and LH (USDA-bLH-I-l) in serum of dairy cows after 50 J18 GnRH given 72 h after implant removal. CoDCeDtrations represent an average of eight cows pa' group [progestogen (+) vs. blank implant (.)]. Cows were implanted previously with either 6 mg of progestogen (norgestotnet) or a blank implant (control) for 6 d, beginDiDg 2 10 5 d postpartum. Standard errors for concentrations of FSH were ± .2 ngIml and for concentrations of LH were ± oS ngIml. Journal of Dairy Science Vol. 74, No.5, 1991
4
~
~
~
~
~
~
0
1
2
3
Days from GnRH Injection Figure 3. Concentrations of estradiol-17~ in serum of dairy cows collected from the beginning of the implant period until 3 d after a 5O-J18 injection of GnRH. Cows
were implanted with 6 mg of progestogen (norgestomet) or a blank implant (control) for 6 d, beginning 2 10 5 d postpartum. Standard errors for average concentrations of estradiol-17~ were ± 1.7 pgIml.
1579
FIRST POSTPARTIJM LUTEAL FUNCTION
Duration of Luteal Phases
Serum Concentrations of PGFM
18 Frequency
pg/ml 2600. -~.. ~
Imj:l1llnJ.J
2000 1600
18
Blank
---+-- Progeatogen
12
_
~
10
_
8
1000
16
14
12-:-1
Short
(e
Normal
(12-18 d)
I
Extended (> 18 d) 7
6 4 2
600 0.L--,--~~~-,--~--.---,---.----r--.---r--,.---.J
-8 -6 -4 -2 0 2 4 6 8 10 12 14 16 16 20
Days from GnRH Injection Figure 4. Concentrations of 13,14-dihydro, 15-ketoprostaglandin F2o: (PGFM) collected from the beginning of the implant period until 20 d after 50 J.1g of GnRH. Cows were implanted with 6 mg of progestogen (norgestomet) or a blank implant (control) for 6 d, beginning 2 to 5 d postpartum. Standard errors for average concentrations of PGFM were ± 20 pg/mJ.
in nonnally cycling COWS (1). Inskeep et al. (10) also observed that follicles from progestogen-treated cows had increased receptors for LH in both granulosa! and thecal cells and higher estradiol concentrations in follicular fluid than corresponding follicles of control cows. Furthennore, progestogen treatment of suckled cows for 9 d altered maturation of the largest follicle, which produced more estradiol and established the dominance of a single follicle (7). In addition, Day et aI. (4) reported that the incidence of short luteal phases was lower in cows receiving an estradiol-17(3 implant from 2 to 40 d postpartum than in untreated controls. Hysterectomy prevented regression of the CL in cycling ewes (11), anestrous ewes (26), and postpartum suckled cows (3) anticipated to have a short luteal lifespan, and luteal lifespan was prolonged with uterine administration of indomethacin in suckled cows induced to ovulate with GnRH (29). We observed prolonged luteal function after the GnRH-induced first ovulation in 12 of our periparturient milked cows with suspected uterine pathology. Active immunization of anestrous beef cows against PGF2a also extended the lifespan of CL anticipated to be short-lived (3). Thus, shortlived CL do not have an inherently short lifespan (2, 3, 11, 26, 29) because the uterus plays an important role in determining the
o
*-Yea Yea-No No-Yea No-No Progestogen - GnRH Response
Figure 5. Frequency of either short, normal, or extended luteal phases in response to treatment with 6 mg of progestogen or a blank implant (control) for 6 d, beginning 2 to 5 d postpartum. The GnRH (SO J.1g) was injected (i.III.) 72 h after removal of implants.
lifespan of the first postpartum CL, Prostaglandin F2a. which is secreted from the uterus, is considered to be the major luteolysin responsible for demise of the CL of the short luteal phase (2, 3, 33). The early demise of the CL induced by premature release of PGF2a might be associated, in part, with deficiencies in the preovulatory follicle that formed the CL of the short luteal phase (1, 10, 11). Recently, CL anticipated to be short-lived were not observed to be more responsive to PGF2a than CL anticipated to have a nonnal lifespan (2). This finding is consistent with the fact that although most of the receptors for PGF2a are found in large luteal cells of the CL (5), there was no difference observed in the properties of large and small luteal cells in short-lived compared with nonnal CL (21). Furthermore, Zollers et aI. (33) reported that oxytocin induced a release of PGF2a on d 5 (d o = estrus) in cows anticipated to have shortlived CL but not in cows pretreated with progestogen that had nonnal luteal phases. They aIso reported that the oxytocin-induced release of PGF2a on d 5 was similar to oxytocin-induced release of PGF2a on d 16 of a nonnaI estrous cycle. It is not known how progestogen treatment affects oxytocin release or what its relationship is to the subsequently lower concentrations of PGF2a. In our study. concentrations of PGFM were lower for 12 d Journal of Dairy Science Vol. 74, No.5, 1991
1580
MEE BT AL.
after GnRH injection in progestogen-treated cows, which substantiated the belief of Troxel and Kesler (30) that the mechanism associated with progestogen treatment involved a reduction in PGF2a secretion mediated by the ovary rather than by the pituitary. Perhaps the higher concentrations of serum estradiol observed in progestogen-treated cows induced uterine progesterone receptors as reported in sheep (32), and when bound to its receptor, progestogen interferes with the induction of oxytocin receptors (13). H this is true, the overall result would be reduced secretion of PGF2a and less probability of a short luteal phase. CONCLUSION
This study provides evidence that pretreatment with progestogen before a GnRH-induced ovulation reduced the incidence of short luteal phases in postpartum milked cows, even when treatment began as early as 2 to 5 d postpartum. These findings and others (6, 7, 10, 11, 18) indicated that pretreatment with progestogen enhances the lifespan and function of the first CL formed after ovulation. However, our progestogen treatment was not as effective in preventing short luteal phases as in earlier studies, perhaps due to a shorter duration of treatment (6 d), beginning much sooner postpartum than in earlier studies. In our study, periparturient milked cows exposed to progestogen before GnRH injection had increased concentrations of estradiol and UI after GnRH and lower concentrations of PGFM in serum, resulting in fewer short luteal phases. It appeared that progestogen had a priming effect on hypothalamic-pituitary function, resulting in increased LH release followed by increased secretion of estradiol by preovulatory follicles that was associated with prolonged postovulatory luteal function relative to controls. ACKNOWLEDGMENTS
We express appreciation to Tammi DelCurto, Karla Parsons, and Betty Hensley for their assistance in the laboratory; to SANOFI Animal Health, Overland Parle, KS for donation of the norgestomet and blank implants; and to Brenda Diederich and Val Stillwell for typing this manuscript. We thank K. Kirton, The Upjohn Company, Kalamazoo, MI for donating Journal of Dairy Science Vol. 74, No.5, 1991
the antiserum to 13,I4-dihydro-15-keto-prostaglandin F2a, Norman Mason, Eli Lilly and Company, Indianapolis, IN for donating the estradiol antiserum; and Doug Bolt, USDAARS, Beltsville, MD, and the Hormone Distribution Office, National Institute of Diabetes and Digestive and Kidney Diseases, Bethesda. MD for donating the pituitary hormone preparations. REFERENCES
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13 McCracken, J. A, W. Schramm, and W. C. Oku1icz.
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24 Smith, M F. 1986. Recent advances in corpus luteum physiology. J. Dairy Sci. 69:911. 25 Smith, M. F., A. W. Lishman, G. S. Lewis, P. G. Harms, M R. Ellersieck, E. K. Inskeep, J. N. Wiltbank, and M S. Amos. 1983. Pituitary and ovarian responses to gonadotropin-releasing hormone, calf removal and progestogen in anestrus beef cows. J. AninI. Sci. 57:418. 26 Soulhee, J. A., M G. Hunter, A. S. Law, and W. Haresign. 1988. Effect of hysterectomy on the short life-cycle corpus luteum produced after GnRH-induced ovulation in the anestrous ewe. J. Reprod. Fertil. 84: 149. 27 Stevenson, J. S., and E. P. Call. 1983. Influence of early estIus, ovulation, and insemination on fertility in postpartum Holstein cows. Theriogenology 19:367. 28 Stewart, R. E., and J. S. Stevenson. 1987. Hormonal, estrual, ovulatory and milk traits in postpartum dairy cows following multiple daily injections of oxytocin. J. Anim. Sci 65:1585. 29 Troxel, T. R., and D. J. Kesler. 1984. Ability of indomethacin to alter prostaglandin metabolite concentrations and to enhance the function of corpora lutea induced in postpartum suckled beef cows. J. Anim. Sci. 59:177. 30 Troxel, T. R., and D. J. Kesler. 1984. The effect of progestin and GnRH treatments on ovarian function and reproductive hormone secretions of anestrous postpartum suckled beef cow. Theriogenology 21:699. 31 Wettemann, R. P. 1980. Postpartum endocrine function of cattle, sheep, and swine. J. Anim. Sci. 51(Suppl. 2):
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Journal of Dairy Science Vol. 74, No.5, 1991
