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Characterization of short luteal cycles in the early post-partum period and their relation to reproductive performance of dairy cows
Animal Reproduction Science, 16 (1988) 215-224
215
Elsevier Science Publishers B.V., Amsterdam - - Printed in The Netherlands
Characterization of Short Luteal Cycles in the Early P o s t - P a r t u m P e r i o d and Their Relation to R e p r o d u c t i v e P e r f o r m a n c e of D a i r y Cows* S. EGER', M. SHEMESH ~, H. SCHINDLER '~'**,S. AMIR 3 and R.H. FOOTE 4
'Advisory Service, Ministry of Agriculture (Israel) "-The Kimrom Veterinary Institute (Israel) :~Institute of Animal Science, Agricultural Research Organization, Bet Dagan 50250 (Israel) 4Department of Animal Science, Cornell University, Ithaca, N Y (U.S.A.) *Contribution from the Agricultural Research Organization, The Volcani Center, Bet Dagan, Israel. No. 1749-E, 1986 series. **Address for correspondence. (Accepted 26 November 1987)
ABSTRACT
Eger, S., Shemesh, M., Schindler, H., Amir, S. and Foote, R.H., 1988. Characterization of short luteal cycles in the early post-partum period and their relation to reproductive performance of dairy cows. Anim. Reprod. Sci., 16: 215-224. The ovarian activity of primiparous and multiparous Israeti-Friesian dairy cows was monitored by progesterone (P4) determination in fat-free milk twice weekly, beginning at calving and continuing until pregnancy was confirmed by palpation, but not later than 150 days post partum. The cows were observed for standing oestrus, thrice daily. Based on the distribution of progesterone concentrations concurrent with inseminations at behavioral oestrus resulting in conceptions or not, 0.5 ng/ml was taken as the dividing value between luteal and non-luteal origins of progesterone. Resumption of luteal activity occurred by 35 days post partum in 99% and 93% of the primiparous and multiparous cows, respectively. The rate of short luteal cycles ( < 11 days) was about 54% in the first, 24% in the second and 20% in the third-fifth luteal cycles post partum. The duration of first luteal cycles was associated with post partum interval. Neither length nor maximum progesterone concentration of the cycle preceding insemination was associated with conception rate. The results indicate that short luteal cycles ( < 11 days), whenever they occur, can be attributed to a functional corpus luteum and not to ovary malfunction.
INTRODUCTION
A post-partum elevation of plasma progesterone (Pt) concentration is generally accepted as indication of resumption of ovarian activity (Lamming, 1978). The time of its occurrence is determined by the minimal level of P4 which is considered to be of luteal origin, i.e., follows an ovulation. Thus, Lam-
0378-4320/88/$03.50
© 1988 Elsevier Science Publishers B.V.
216 ming and Bulman (1976) used a concentration of at least 3 n g / m l in whole milk as being indicative of luteal activity, whereas Mather et al. (1978) used a level of 2 n g / m l in cream as the criterion. Henricks et al. (1972), using blood plasma as substrate, considered any rise in P4 following an oestrogen peak as being of luteal origin. Robertson (1972) found a basal level of <0.5 ng/ml during the immediate post-partum period and considered a rise above this level as originating from luteal tissue. He, however, realized that some of the early post-partum progesterone peaks could have been associated with follicle luteinization rather than with ovulation. The resumption of ovarian activity has been reported to be initiated at various intervals post partum: < 20-40 days (Lamming and Bulman, 1976), < 1035 days (Henricks et al., 1972), 12-56 days (Mather et al., 1978). Lamming et al. (1981) and Schams et al. (1978) reported that about 50% of the first increases of progesterone concentration are of short duration and that there are different opinions as to their causes. Short luteal phases in second or later oestrous cycles have apparently not yet been studied. It would appear that the short luteal cycles, whenever they occur, deserve additional study. This paper presents data characterizing first and later short luteal cycles in relation to post-partum interval, behavioral oestrus and other luteal cycles, their durations and progesterone concentrations, and their relation to reproductive performance and management. MATERIALSAND METHODS Seventy-four calving cycles of primiparous and 163 calving cycles of multiparous Israeli-Friesian cows of the experimental herd were analyzed in this study. The 163 cycles included 90 cycles of either primiparous or multiparous cows, recurring during the experimental period. The cows were housed in free stall barns and milked three times a day. They were observed for behavioral oestrus (standing when being mounted by other cows) during 30 min at 06.00, 14.00 and 18.00 h. During the greater part of the experimental period a penisdeviated teaser bull was also used. Animals exhibiting behavioral oestrus were inseminated once, at 08.00 h, with semen of one of three bulls known for high fertility. Ovarian activity was monitored by P4 determination in fat-free milk samples. Milk samples were taken twice weekly, i.e., at 3- and 4-day intervals directly from the weigh jar at the end of the morning milking, beginning at calving and continuing during 150 days post partum, or until pregnancy was confirmed by palpation. Fat-free samples were prepared by centrifuging at 1000 r.p.m, for 20 min at room temperature. P4 was determined by radioimmunoassay described by Shemesh and Hansel (1975) and Shemesh et al. (1978), who used an antibody raised against progesterone-ll-hemisuccinate-BSA and showing less than 0.01% cross-reaction
217
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PARTUM
Fig. 1. Post-partumprogesteronelevels. 0, Behavioraloestrus; LC, first luteai cyclepost partum; AI, artificial insemination. Note: the first luteal cycleis precededand followedby behavioral oestrus. The consecutivecyclesstart at days 26, 41, 54, 61, 68, 104, 122, 138. with cortisol, estradiol-17fl, testosterone, cholesterol, 17a-hydroxyprogesterone, estrone, corticosterone, androstendione. In this procedure the intraassay coefficient of variation within pairs of samples was 7.9% and the interassay coefficient of variation was 10.2%. Progesterone values were computerized and individual curves were obtained after converting sampling dates to days post partum. The duration of a luteal phase or cycle was defined as the period from the time when P4 concentration rose continuously from a lowest value ( _<0.5 ng/ ml) to above 0.5 ng/ml until the following abrupt decrease to 0.5 ng/ml or below (Fig. 1 ). Due to the twice-a-week sampling procedure, allowance must be made for the possibility that the actual rise in the P4 curve may have occurred 1 or 2 days later, whereas the actual end of the phase may have occurred 1 or 2 days earlier. The definition of short luteal cycles as < 11 days was adopted from Lamming et al. (1981). Differences between groups were analyzed by chi-square procedure. RESULTS Progesterone concentration in milk samples concurrent with inseminations at behavioral oestrus was taken as being of non-luteal origin. As shown in Table 1, P4 values in 98% of the conceiving and in 92% of the non-conceiving cows did not exceed 0.3 ng/ml at standing oestrus. There were no values between 0.31 and 0.5 ng/ml. Based on these findings, concentrations exceeding 0.5 ng/ml were assumed to originate from a corpus luteum. The first rise of P4 above 0.5 ng/ml was considered to be the beginning of luteal activity, and representing the start of the first post-partum cycle irrespective of its duration or the interval to the consecutive cycle. The distribution of the beginning of the luteal activity is shown in Table 2. Luteal activity occurred within 35 days of calving in 99 % of the primiparous and in 93 % of the
218 TABLE 1 Progesterone level at insemination of cows and heifers during fertile and non-fertile behavioral estrus Progesterone (ng/ml)
Non-fertile oestrus*
Fertile oestrus No. of insem.
To of all insem.
No. of insem.
Toof all insem.
0.0 0.01-0.3 0.31-0.5 0.51-0.7
59 8 -1
86.7 11.7 -1.6
83 11 -6
81.4 10.8
Total
68
100.0
102
100.0
5.8
*Two cows in the non-fertile oestrus group had P4 values of 1.4 and 1.8 ng/ml. TABLE 2 Initiation of luteal activity after calving Days after calving $5 6-10 11-15 16-20 21-25 26-30 31-35 36-56 Total
Primiparous
Multiparous
No. of cows
Cum. To
6 20 16 15 4 7 5 1
8 35 57 77 82 92 99 100
74
No. of cows 20 29 34 28 21 13 7 11
Cum. To 12 30 51 68 81 89 93 100
163
m u l t i p a r o u s cows. T h e m e a n i n t e r v a l w a s 15.5 ___9.4 a n d 17.5 ___11.1 d a y s for p r i m i p a r o u s a n d m u l t i p a r o u s cows, respectively. S e c o n d cycles s t a r t e d a t 3.9 + 5.6 d a y s a n d 4.9 +_ 7.2 d a y s a f t e r t h e t e r m i n a t i o n of t h e first cycle in p r i m i p a r o u s a n d m u l t i p a r o u s cows, respectively. I n b o t h groups, a b o u t 73% of t h e 2 n d luteal cycles w e r e r e s u m e d w i t h i n 5 d a y s of t h e e n d o f t h e first one. All t h e r e s t w e r e r e s u m e d w i t h i n 6 - 2 5 d a y s in p r i m i p a r o u s a n d 6 - 3 5 d a y s in m u l t i p a r o u s cows. I n o u r m a t e r i a l , a m o n g 237 first, 209 s e c o n d a n d 404 t h i r d - f i f t h cycles, t h e i n c i d e n c e o f t h e s h o r t cycles ( < 11 d a y s ) d e c l i n e d s i g n i f i c a n t l y ( P < 0.001) f r o m 53.6% in t h e f i r s t to 23.9% in t h e second, a n d 20.2% in t h e s u b s e q u e n t cycles. T h e r e f o r e , we w e r e i n t e r e s t e d in c o m p a r i n g m a x i m u m P4 c o n c e n t r a t i o n s in s h o r t cycles o f d i f f e r e n t o r d e r n u m b e r w i t h e a c h o t h e r a n d w i t h t h a t
219 TABLE 3 Distribution of short luteal cycles ( < 11 days long) by maximum progesterone concentration and post-partum order number Maximum progesterone concentration (ng/ml)
Cycle* First <11d
>12d
30a 37 12 9 12
65 20 21 17 36
0.51-1.0 1.1 -2.0 2.1 -3.0 3.1 -4.0 24.1 Total
127
106
Second
Third-Fifth
<11 d
<11 d
17c 49 18 6 10
32d 26 19 8 15
49
80
abp < 0.001; ~ P < 0.05; ~ P < 0.001. *Percent of all cycles. IO0
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DAYS POST PARTUM Fig. 2. Length distribution of first luteal cycles in relation to post-partum interval. The curves represent the cumulative percentages of the cycles in each length class during the post-partum period. Length classes (days): ~<7 ( n = 7 8 ) , 8-11 ( n = 4 9 ) , 12-16 ( n = 3 0 ) , 17-21 ( n = 4 9 ) , 22-26 (n=14).
220 TABLE 4 Incidence of behavioral oestrus preceding first luteal cycles of different durations Length of first luteal cycle (days)
Primiparous
Multiparous
Oestruses (no.)
11 12-16 17-21 22-26 227 Total
1 0 6 2 1
Oestruses
%
Luteal cycles (no.)
(no.)
%
10 00 60 20 10
37 8 16 5 8
11 2 8 1 3
44 8 32 4 12
74
25
10
Luteal cycles (no.) 90 22 32 9 9 163
TABLE 5 Conception rates from first inseminations* at behavioral oestrus following luteal cycles of different durations Duration of luteal cycle (days)
No. of inseminations
Conception rate (%)
11 12-15 16-18 19-21 22-28 229
52** 73 50 49 31 16
52 40 38 59 58 62
*Oestruses at inseminations were of different order number post partum. **Including about one-third of re-inseminationsat the following oestrus. TABLE 6 Conception rates from first inseminations at behavioral estrus following luteal cycles with differ. ent progesterone peaks Maximum progesterone concentration preceding insemination
No. of inseminations
Conception rate (%)
0.6-1.0 1.1-2.0 2.1-3.0 3.1-4.0 >-4.1
3 15 47 27 93
33 47 47 63 48
221
of first longer cycles ( > 12 days) (Table 3). Distribution of Pt concentrations was similar among short cycles of different order numbers, but it was different between short and long cycles, with the latter distinctly having higher P4 concentration ( P < 0.001). As shown in Fig. 2 the duration of first luteal cycles is associated with postpartum interval. Thus, within 15 days post partum, about 70% of the 7 day, 60% of the 8-11 day, 50% of the 12-16 day, 30% of the 17-21 day and almost none of the 22-26 day cycles had started ( P < 0.01 ). We next examined the occurrence of behavioral oestrus in relation to a consecutive first luteal cycle. As can be seen from Table 4, about 15% of the first luteal cycles in both primiparous and multiparous cows were preceded by behavioral oestrus. In primiparous cows, a tendency appeared for the long cycles to be preceded by a behavioral oestrus. However, multiparous cows were as likely to display oestrus preceding cycles of any length. We compared conception rates from insemination during behavioral oestrus preceded by luteal cycles of different durations (Table 5 ) and of different maximum P4 concentrations (Table 6). The conception rate from inseminations after a short luteal cycle (52%) was not significantly different from the rates from inseminations after the longer cycles., Also, the level of maximum progesterone concentration in the cycle preceding insemination was not significantly associated with conception rate. DISCUSSION
The very early resumption of luteal activity post partum which appeared in our data, is in accord with Schallenberger et al. (1984) who found that by 5 days post partum pulsatile release of physiological levels of LH and FSH was established. They stated that "also the first luteal phase was preceded by ovulation". Castenson et al. (1976), too, have shown by visual and histological examination that first post-partum luteal activity, without special reference to its length, may result from ovulation and formation of a corpus luteum. On the other hand, Schams et al. (1978) suggest that the first short luteal cycles derive from an inadequate formation of the corpus luteum. This inadequacy is, according to Niswender et al. (1976), a result of insufficient blood supply for the first corpus luteum, or insufficient LH availability. Manns et al. (1983) clearly demonstrated in beef cows that in eight out of nine animals short luteal activities originated from a histologically typical corpus luteum preceded by ovulation. They assumed that such corpora lutea lost their ability to secrete P4, because they were not responsive to gonadotrophic stimulation. Kindahl et al. (1982) suggested that post-partum prostaglandin release may be the cause of the higher incidence of short luteal phases when the first ovulation occurs relatively early post partum. However, secretion of P4 by the adrenal gland (Balfour et al., 1957) cannot be disregarded especially when
222 interpreting P4 levels which are only moderately above basal. Donaldson et al. (1970) and Robertson (1972) suggested that first luteal cycles post partum which are characterized by a high rate of short cycles, may originate, in part, from luteinization of follicles. However, the incidence of this process seems to be low, as indicated by the observations of Castenson et al. (1976) in which luteinization occurred in only one out of eight heifers. The fact that short first luteal cycles were preceded by standing oestrus (Table 4, Fig. 1 ) in our study is in agreement with Ramirez-Godinez et al. ( 1982 ) who demonstrated, by means of oviductal flushings, that previously unoestrous beef cows ovulated at their first post-weaning oestrus, followed by a short luteal cycle. This may show that short luteal cycles preceded by oestrus are controlled by a corpus luteum. The fact that the frequency distribution of maximum P4 concentration is similar in all short cycles independent of their order number {Table 3) also points to this conclusion. Our data showed no effect of the magnitude of maximum progesterone concentration on the effectiveness of the subsequent insemination, although its variation was rather extreme. This finding is in agreement with Bulman and Lamming (1978) using milk and with Stevenson et al. (1985) using serum as substrate who found that P4 levels were similar during about 20 days before insemination among cows that conceived or failed to conceive. The results of the latter also indicate that the lack of association is not bound to the substrate. However, Folman et al. (1973) determining plasma P4 levels, Fonseca et al. (1983) determining P4 levels in serum, and Carstairs et al. (1980) who determined peak concentration of serum progesterone during the oestrous cycle preceding insemination, did find an association between progesterone concentrations and conception rates. Also, the variations in the length of luteal cycles in our study could not clearly be associated with subsequent conception rates. We have no explanation for the relatively low conception rates from inseminations after luteal cycles of 12-15 and 16-18 days, which seem to be the most frequent ones in our data. In summary, it appears that the first post-partum luteal cycles, irrespective of their length, can be attributed to a functional corpus luteum, and that short luteal cycles, if they occur in healthy cows, should not be considered as ovarian malfunction and the consecutive oestrus can be utilized for inseminations when its timing fits the respective reproductive management program. ACKNOWLEDGEMENTS This research was supported by a grant from the United States-Israel Binational Agricultural Research and Development Fund - BARD. The authors are grateful to Mrs. Miriam Zarchi, Department of Statistics and Experimental Design, for programming the computer output.
223 REFERENCES Balfour, W.E., Comline, R.S. and Short, R.V., 1957. Secretion of progesterone by adrenal gland. Nature (London), 180: 1480-1481. Bulman, D.C. and Lamming, G.E., 1978. Milk progesterone levels in relation to conception, repeat breeding and factors influencing acyclicity in dairy cows. J. Reprod. Fertil., 54: 447-458. Carstairs, J.A., Morrow, D.A. and Emery, R.S., 1980. Postpartum reproductive function of dairy cows as influenced by energy and phosphorus status. J. Anim. Sci., 51: 1122-1130. Castenson, P.E., Sorensen, A.M., Jr., Cobos, C.R. and Fleeger, J.L., 1976. Source of postpartum P and 20fl-OHP preceding estrus in heifers. J. Anim. Sci., 43:277 (Abstract). Donaldson, L.E., Basset, J.M. and Thorburn, G.D., 1970. Peripheral plasma progesterone concentration of cows during puberty, estrous cycles, pregnancy and lactation and the effects of undernutrition or exogenous oxytocin on progesterone concentration. J. Endocrinol., 48: 599614. Folman, Y., Rosenberg, M., Herz, Z. and Davidson, M., 1973. The relationship between plasma progesterone concentration and conception in postpartum dairy cows maintained on two levels of nutrition. J. Reprod. Fertil., 34: 267-278. Fonseca, F.A., Britt, J.H., McDaniel, B.T., Wilk, J.C. and Rakes, A.H., 1983. Reproductive traits of Holsteins and Jerseys. Effects of age, milk yield, and clinical abnormalities on involution of cervix and uterus, ovulation, estrous cycles, detection of estrus, conception rate, and days open. J. Dairy Sci., 6: 1128-1147. Henricks, D.M., Dickey, J.F., Hill, J.R. and Johnston, W.E., 1972. Plasma estrogen and progesterone levels after mating and during late pregnancy and postpartum in cows. Endocrinology, 90: 1336-1342. Kindahl, H., Edqvist, L.E., Larsson, K. and Malmqvist, A., 1982. Influence of prostaglandins on ovarian function post partum. In: H. Karg and E. Schallenberger (Editors), Factors Influencing Fertility in the Postpartum Dairy Cow. Martinus-Nijhoff Publishers, The Hague, pp. 173196. Lamming, G.E., 1978. Reproduction during lactation. In: D.B. Crighton, N.B. Haynes, C.R. Foxcroft and G.E. Lamming (Editors), Control of Ovulation. Butterworths, London, pp. 335-353. Lamming, G.E. and Bulman, D.C., 1976. The use of progesterone radioimmunoassay in the diagnosis and treatment of subfertility in dairy cows. Br. Vet. J., 132: 507-517. Lamming, G.E., Wathes, D.C. and Peters, A.R., 1981. Endocrine patterns of the post-partum cow. J. Reprod. Fertil., Suppl., 30: 155-170. Manns, J.G., Humphrey, W.D., Flood, P.F., Mapletoft, R.J., Rawlings, N. and Cheng, K.W., 1983. Endocrine profiles and functional characteristics of corpora lutea following onset of postpartum ovarian activity in beef cows. Can. J. Anim. Sci., 63: 331-347. Mather, E.C., Camper, P.M., Vahdat, F., Whitmore, H.L. and Gustafsson, B.G., 1978. Assessment of' ovarian activity in the postpartum dairy cow by use of milk progesterone assay. Theriogenology, 10: 119-129. Niswender, G.D., Reimers, T.J., Diekman, M.A. and Nett, T.M., 1976. Blood flow: a mediator of ovarian function. Biol. Reprod., 14: 64-81. Ramirez-Godinez, J.A., Kiracofe, G.H., Carnahan, D.L., Spire, M.F., Beeman, K.B., Stevenson, J.S. and Schalles, R.R., 1982. Evidence for ovulation and fertilization in beef cows with short estrous cycles. Theriogenology, 17: 409-414. Robertson, H.A., 1972. Sequential changes in plasma progesterone in the cow during the estrous cycle, pregnancy, at parturition and postpartum. Can. J. Anita. Sci., 52: 645-658. Schallenberger, E., Waiters, D.L., Oschmann, S.J. and Meyer, H.H.D., 1984. Endocrine changes during the early postpartum period in dairy cattle. In: Proc. 10th Int. Congr. Animal Reproduction and Artificial Insemination (Urbana-Champaign), Vol. 4, pp. III-9-III-16. Schams, D., Schallenberger, E., Menzer, Ch., Stangl, J., Zottmeier, K., Hoffmann, B. and Karg,
224 H., 1978. Profiles of LH, FSH and progesterone in postpartum dairy cows and their relationship to commencement of cyclic functions. Theriogenology, 10: 453-467. Shemesh, M. and Hansel, W., 1975. Levels of prostaglandin F {PGF) in bovine endometrium, uterine venous, ovarian arterial and jugular plasma during the estrous cycle. Proc. Soc. Exp. Biol. Med., 148: 123-126. Shemesh, M., Ayalon, N., Shalev, E., Nerya, A. Schindler, H. and Milguir, F., 1978. Milk progesterone measurement in dairy cows: correlation with estrus and pregnancy determination. Theriogenology, 9: 343-351. Stevenson, J.S., Lucy, M.C. and Call, E.P., 1985. Serum progesterone before and after insemination and gonadotropin-releasing hormone (GnRH) in Holstein cows. J. Anim. Sci., 61 {Suppl. 1): 114 {Abstract).
215
Elsevier Science Publishers B.V., Amsterdam - - Printed in The Netherlands
Characterization of Short Luteal Cycles in the Early P o s t - P a r t u m P e r i o d and Their Relation to R e p r o d u c t i v e P e r f o r m a n c e of D a i r y Cows* S. EGER', M. SHEMESH ~, H. SCHINDLER '~'**,S. AMIR 3 and R.H. FOOTE 4
'Advisory Service, Ministry of Agriculture (Israel) "-The Kimrom Veterinary Institute (Israel) :~Institute of Animal Science, Agricultural Research Organization, Bet Dagan 50250 (Israel) 4Department of Animal Science, Cornell University, Ithaca, N Y (U.S.A.) *Contribution from the Agricultural Research Organization, The Volcani Center, Bet Dagan, Israel. No. 1749-E, 1986 series. **Address for correspondence. (Accepted 26 November 1987)
ABSTRACT
Eger, S., Shemesh, M., Schindler, H., Amir, S. and Foote, R.H., 1988. Characterization of short luteal cycles in the early post-partum period and their relation to reproductive performance of dairy cows. Anim. Reprod. Sci., 16: 215-224. The ovarian activity of primiparous and multiparous Israeti-Friesian dairy cows was monitored by progesterone (P4) determination in fat-free milk twice weekly, beginning at calving and continuing until pregnancy was confirmed by palpation, but not later than 150 days post partum. The cows were observed for standing oestrus, thrice daily. Based on the distribution of progesterone concentrations concurrent with inseminations at behavioral oestrus resulting in conceptions or not, 0.5 ng/ml was taken as the dividing value between luteal and non-luteal origins of progesterone. Resumption of luteal activity occurred by 35 days post partum in 99% and 93% of the primiparous and multiparous cows, respectively. The rate of short luteal cycles ( < 11 days) was about 54% in the first, 24% in the second and 20% in the third-fifth luteal cycles post partum. The duration of first luteal cycles was associated with post partum interval. Neither length nor maximum progesterone concentration of the cycle preceding insemination was associated with conception rate. The results indicate that short luteal cycles ( < 11 days), whenever they occur, can be attributed to a functional corpus luteum and not to ovary malfunction.
INTRODUCTION
A post-partum elevation of plasma progesterone (Pt) concentration is generally accepted as indication of resumption of ovarian activity (Lamming, 1978). The time of its occurrence is determined by the minimal level of P4 which is considered to be of luteal origin, i.e., follows an ovulation. Thus, Lam-
0378-4320/88/$03.50
© 1988 Elsevier Science Publishers B.V.
216 ming and Bulman (1976) used a concentration of at least 3 n g / m l in whole milk as being indicative of luteal activity, whereas Mather et al. (1978) used a level of 2 n g / m l in cream as the criterion. Henricks et al. (1972), using blood plasma as substrate, considered any rise in P4 following an oestrogen peak as being of luteal origin. Robertson (1972) found a basal level of <0.5 ng/ml during the immediate post-partum period and considered a rise above this level as originating from luteal tissue. He, however, realized that some of the early post-partum progesterone peaks could have been associated with follicle luteinization rather than with ovulation. The resumption of ovarian activity has been reported to be initiated at various intervals post partum: < 20-40 days (Lamming and Bulman, 1976), < 1035 days (Henricks et al., 1972), 12-56 days (Mather et al., 1978). Lamming et al. (1981) and Schams et al. (1978) reported that about 50% of the first increases of progesterone concentration are of short duration and that there are different opinions as to their causes. Short luteal phases in second or later oestrous cycles have apparently not yet been studied. It would appear that the short luteal cycles, whenever they occur, deserve additional study. This paper presents data characterizing first and later short luteal cycles in relation to post-partum interval, behavioral oestrus and other luteal cycles, their durations and progesterone concentrations, and their relation to reproductive performance and management. MATERIALSAND METHODS Seventy-four calving cycles of primiparous and 163 calving cycles of multiparous Israeli-Friesian cows of the experimental herd were analyzed in this study. The 163 cycles included 90 cycles of either primiparous or multiparous cows, recurring during the experimental period. The cows were housed in free stall barns and milked three times a day. They were observed for behavioral oestrus (standing when being mounted by other cows) during 30 min at 06.00, 14.00 and 18.00 h. During the greater part of the experimental period a penisdeviated teaser bull was also used. Animals exhibiting behavioral oestrus were inseminated once, at 08.00 h, with semen of one of three bulls known for high fertility. Ovarian activity was monitored by P4 determination in fat-free milk samples. Milk samples were taken twice weekly, i.e., at 3- and 4-day intervals directly from the weigh jar at the end of the morning milking, beginning at calving and continuing during 150 days post partum, or until pregnancy was confirmed by palpation. Fat-free samples were prepared by centrifuging at 1000 r.p.m, for 20 min at room temperature. P4 was determined by radioimmunoassay described by Shemesh and Hansel (1975) and Shemesh et al. (1978), who used an antibody raised against progesterone-ll-hemisuccinate-BSA and showing less than 0.01% cross-reaction
217
AJ 2 0.~ 0
-0 8
0 0 20
40
0 50
I00 DAYS P O S T
.
A_ ~__i.
.
.
.
.
.
_
150
PARTUM
Fig. 1. Post-partumprogesteronelevels. 0, Behavioraloestrus; LC, first luteai cyclepost partum; AI, artificial insemination. Note: the first luteal cycleis precededand followedby behavioral oestrus. The consecutivecyclesstart at days 26, 41, 54, 61, 68, 104, 122, 138. with cortisol, estradiol-17fl, testosterone, cholesterol, 17a-hydroxyprogesterone, estrone, corticosterone, androstendione. In this procedure the intraassay coefficient of variation within pairs of samples was 7.9% and the interassay coefficient of variation was 10.2%. Progesterone values were computerized and individual curves were obtained after converting sampling dates to days post partum. The duration of a luteal phase or cycle was defined as the period from the time when P4 concentration rose continuously from a lowest value ( _<0.5 ng/ ml) to above 0.5 ng/ml until the following abrupt decrease to 0.5 ng/ml or below (Fig. 1 ). Due to the twice-a-week sampling procedure, allowance must be made for the possibility that the actual rise in the P4 curve may have occurred 1 or 2 days later, whereas the actual end of the phase may have occurred 1 or 2 days earlier. The definition of short luteal cycles as < 11 days was adopted from Lamming et al. (1981). Differences between groups were analyzed by chi-square procedure. RESULTS Progesterone concentration in milk samples concurrent with inseminations at behavioral oestrus was taken as being of non-luteal origin. As shown in Table 1, P4 values in 98% of the conceiving and in 92% of the non-conceiving cows did not exceed 0.3 ng/ml at standing oestrus. There were no values between 0.31 and 0.5 ng/ml. Based on these findings, concentrations exceeding 0.5 ng/ml were assumed to originate from a corpus luteum. The first rise of P4 above 0.5 ng/ml was considered to be the beginning of luteal activity, and representing the start of the first post-partum cycle irrespective of its duration or the interval to the consecutive cycle. The distribution of the beginning of the luteal activity is shown in Table 2. Luteal activity occurred within 35 days of calving in 99 % of the primiparous and in 93 % of the
218 TABLE 1 Progesterone level at insemination of cows and heifers during fertile and non-fertile behavioral estrus Progesterone (ng/ml)
Non-fertile oestrus*
Fertile oestrus No. of insem.
To of all insem.
No. of insem.
Toof all insem.
0.0 0.01-0.3 0.31-0.5 0.51-0.7
59 8 -1
86.7 11.7 -1.6
83 11 -6
81.4 10.8
Total
68
100.0
102
100.0
5.8
*Two cows in the non-fertile oestrus group had P4 values of 1.4 and 1.8 ng/ml. TABLE 2 Initiation of luteal activity after calving Days after calving $5 6-10 11-15 16-20 21-25 26-30 31-35 36-56 Total
Primiparous
Multiparous
No. of cows
Cum. To
6 20 16 15 4 7 5 1
8 35 57 77 82 92 99 100
74
No. of cows 20 29 34 28 21 13 7 11
Cum. To 12 30 51 68 81 89 93 100
163
m u l t i p a r o u s cows. T h e m e a n i n t e r v a l w a s 15.5 ___9.4 a n d 17.5 ___11.1 d a y s for p r i m i p a r o u s a n d m u l t i p a r o u s cows, respectively. S e c o n d cycles s t a r t e d a t 3.9 + 5.6 d a y s a n d 4.9 +_ 7.2 d a y s a f t e r t h e t e r m i n a t i o n of t h e first cycle in p r i m i p a r o u s a n d m u l t i p a r o u s cows, respectively. I n b o t h groups, a b o u t 73% of t h e 2 n d luteal cycles w e r e r e s u m e d w i t h i n 5 d a y s of t h e e n d o f t h e first one. All t h e r e s t w e r e r e s u m e d w i t h i n 6 - 2 5 d a y s in p r i m i p a r o u s a n d 6 - 3 5 d a y s in m u l t i p a r o u s cows. I n o u r m a t e r i a l , a m o n g 237 first, 209 s e c o n d a n d 404 t h i r d - f i f t h cycles, t h e i n c i d e n c e o f t h e s h o r t cycles ( < 11 d a y s ) d e c l i n e d s i g n i f i c a n t l y ( P < 0.001) f r o m 53.6% in t h e f i r s t to 23.9% in t h e second, a n d 20.2% in t h e s u b s e q u e n t cycles. T h e r e f o r e , we w e r e i n t e r e s t e d in c o m p a r i n g m a x i m u m P4 c o n c e n t r a t i o n s in s h o r t cycles o f d i f f e r e n t o r d e r n u m b e r w i t h e a c h o t h e r a n d w i t h t h a t
219 TABLE 3 Distribution of short luteal cycles ( < 11 days long) by maximum progesterone concentration and post-partum order number Maximum progesterone concentration (ng/ml)
Cycle* First <11d
>12d
30a 37 12 9 12
65 20 21 17 36
0.51-1.0 1.1 -2.0 2.1 -3.0 3.1 -4.0 24.1 Total
127
106
Second
Third-Fifth
<11 d
<11 d
17c 49 18 6 10
32d 26 19 8 15
49
80
abp < 0.001; ~ P < 0.05; ~ P < 0.001. *Percent of all cycles. IO0
--
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90
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DAYS POST PARTUM Fig. 2. Length distribution of first luteal cycles in relation to post-partum interval. The curves represent the cumulative percentages of the cycles in each length class during the post-partum period. Length classes (days): ~<7 ( n = 7 8 ) , 8-11 ( n = 4 9 ) , 12-16 ( n = 3 0 ) , 17-21 ( n = 4 9 ) , 22-26 (n=14).
220 TABLE 4 Incidence of behavioral oestrus preceding first luteal cycles of different durations Length of first luteal cycle (days)
Primiparous
Multiparous
Oestruses (no.)
11 12-16 17-21 22-26 227 Total
1 0 6 2 1
Oestruses
%
Luteal cycles (no.)
(no.)
%
10 00 60 20 10
37 8 16 5 8
11 2 8 1 3
44 8 32 4 12
74
25
10
Luteal cycles (no.) 90 22 32 9 9 163
TABLE 5 Conception rates from first inseminations* at behavioral oestrus following luteal cycles of different durations Duration of luteal cycle (days)
No. of inseminations
Conception rate (%)
11 12-15 16-18 19-21 22-28 229
52** 73 50 49 31 16
52 40 38 59 58 62
*Oestruses at inseminations were of different order number post partum. **Including about one-third of re-inseminationsat the following oestrus. TABLE 6 Conception rates from first inseminations at behavioral estrus following luteal cycles with differ. ent progesterone peaks Maximum progesterone concentration preceding insemination
No. of inseminations
Conception rate (%)
0.6-1.0 1.1-2.0 2.1-3.0 3.1-4.0 >-4.1
3 15 47 27 93
33 47 47 63 48
221
of first longer cycles ( > 12 days) (Table 3). Distribution of Pt concentrations was similar among short cycles of different order numbers, but it was different between short and long cycles, with the latter distinctly having higher P4 concentration ( P < 0.001). As shown in Fig. 2 the duration of first luteal cycles is associated with postpartum interval. Thus, within 15 days post partum, about 70% of the 7 day, 60% of the 8-11 day, 50% of the 12-16 day, 30% of the 17-21 day and almost none of the 22-26 day cycles had started ( P < 0.01 ). We next examined the occurrence of behavioral oestrus in relation to a consecutive first luteal cycle. As can be seen from Table 4, about 15% of the first luteal cycles in both primiparous and multiparous cows were preceded by behavioral oestrus. In primiparous cows, a tendency appeared for the long cycles to be preceded by a behavioral oestrus. However, multiparous cows were as likely to display oestrus preceding cycles of any length. We compared conception rates from insemination during behavioral oestrus preceded by luteal cycles of different durations (Table 5 ) and of different maximum P4 concentrations (Table 6). The conception rate from inseminations after a short luteal cycle (52%) was not significantly different from the rates from inseminations after the longer cycles., Also, the level of maximum progesterone concentration in the cycle preceding insemination was not significantly associated with conception rate. DISCUSSION
The very early resumption of luteal activity post partum which appeared in our data, is in accord with Schallenberger et al. (1984) who found that by 5 days post partum pulsatile release of physiological levels of LH and FSH was established. They stated that "also the first luteal phase was preceded by ovulation". Castenson et al. (1976), too, have shown by visual and histological examination that first post-partum luteal activity, without special reference to its length, may result from ovulation and formation of a corpus luteum. On the other hand, Schams et al. (1978) suggest that the first short luteal cycles derive from an inadequate formation of the corpus luteum. This inadequacy is, according to Niswender et al. (1976), a result of insufficient blood supply for the first corpus luteum, or insufficient LH availability. Manns et al. (1983) clearly demonstrated in beef cows that in eight out of nine animals short luteal activities originated from a histologically typical corpus luteum preceded by ovulation. They assumed that such corpora lutea lost their ability to secrete P4, because they were not responsive to gonadotrophic stimulation. Kindahl et al. (1982) suggested that post-partum prostaglandin release may be the cause of the higher incidence of short luteal phases when the first ovulation occurs relatively early post partum. However, secretion of P4 by the adrenal gland (Balfour et al., 1957) cannot be disregarded especially when
222 interpreting P4 levels which are only moderately above basal. Donaldson et al. (1970) and Robertson (1972) suggested that first luteal cycles post partum which are characterized by a high rate of short cycles, may originate, in part, from luteinization of follicles. However, the incidence of this process seems to be low, as indicated by the observations of Castenson et al. (1976) in which luteinization occurred in only one out of eight heifers. The fact that short first luteal cycles were preceded by standing oestrus (Table 4, Fig. 1 ) in our study is in agreement with Ramirez-Godinez et al. ( 1982 ) who demonstrated, by means of oviductal flushings, that previously unoestrous beef cows ovulated at their first post-weaning oestrus, followed by a short luteal cycle. This may show that short luteal cycles preceded by oestrus are controlled by a corpus luteum. The fact that the frequency distribution of maximum P4 concentration is similar in all short cycles independent of their order number {Table 3) also points to this conclusion. Our data showed no effect of the magnitude of maximum progesterone concentration on the effectiveness of the subsequent insemination, although its variation was rather extreme. This finding is in agreement with Bulman and Lamming (1978) using milk and with Stevenson et al. (1985) using serum as substrate who found that P4 levels were similar during about 20 days before insemination among cows that conceived or failed to conceive. The results of the latter also indicate that the lack of association is not bound to the substrate. However, Folman et al. (1973) determining plasma P4 levels, Fonseca et al. (1983) determining P4 levels in serum, and Carstairs et al. (1980) who determined peak concentration of serum progesterone during the oestrous cycle preceding insemination, did find an association between progesterone concentrations and conception rates. Also, the variations in the length of luteal cycles in our study could not clearly be associated with subsequent conception rates. We have no explanation for the relatively low conception rates from inseminations after luteal cycles of 12-15 and 16-18 days, which seem to be the most frequent ones in our data. In summary, it appears that the first post-partum luteal cycles, irrespective of their length, can be attributed to a functional corpus luteum, and that short luteal cycles, if they occur in healthy cows, should not be considered as ovarian malfunction and the consecutive oestrus can be utilized for inseminations when its timing fits the respective reproductive management program. ACKNOWLEDGEMENTS This research was supported by a grant from the United States-Israel Binational Agricultural Research and Development Fund - BARD. The authors are grateful to Mrs. Miriam Zarchi, Department of Statistics and Experimental Design, for programming the computer output.
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224 H., 1978. Profiles of LH, FSH and progesterone in postpartum dairy cows and their relationship to commencement of cyclic functions. Theriogenology, 10: 453-467. Shemesh, M. and Hansel, W., 1975. Levels of prostaglandin F {PGF) in bovine endometrium, uterine venous, ovarian arterial and jugular plasma during the estrous cycle. Proc. Soc. Exp. Biol. Med., 148: 123-126. Shemesh, M., Ayalon, N., Shalev, E., Nerya, A. Schindler, H. and Milguir, F., 1978. Milk progesterone measurement in dairy cows: correlation with estrus and pregnancy determination. Theriogenology, 9: 343-351. Stevenson, J.S., Lucy, M.C. and Call, E.P., 1985. Serum progesterone before and after insemination and gonadotropin-releasing hormone (GnRH) in Holstein cows. J. Anim. Sci., 61 {Suppl. 1): 114 {Abstract).