Evaluation of the lytic response of prostaglandin F2 alpha in Zebu cattle based on serum progesterone

To evaluate by means of blood progesterone levels and estrous expression the effect of the injection of 25 mg of PGF2alpha in Zebu cows, 17 Indobrazil cows with a palpable corpus luteum (CL) were injected with PGF2alpha and blood samples taken every 6 h in Experiment I. In Experiment II, 15 cows from the previous experiment at the same stage of diestrus were injected with PGF2alpha and bled every 4 h for 5 d. Progesterone levels had declined by 50% 6 h after injection in all cows and dropped to below 1 ng/ml by 30 h. Estrus was observed in 47% of the animals in Experiment I and 60% in Experiment II. Ovulation was detected accurately in 29% of the animals at 33.6 +/- 11.6 h after the onset of estrus. The correlation between finding a CL by rectal palpation and levels of progesterone higher than 1 ng/ml of blood was 86 and 93% in Experiments I and II, respectively. These studies indicate that the injection of 25 mg of PGF2alpha is sufficient to produce luteolysis in Zebu cattle, although estrous expression is poor.     

Serum progesterone concentration in pyometritic and normal postpartum dairy cows

Two studies were conducted to evaluate the concentration of serum progesterone in pyometritic cows and relate it to palpation of ovarian structures per rectum . In Trial 1, serum samples from 34 pyometritic cows were assayed for progesterone. Mean serum progesterone concentrations were 6.8 +/- 0.7 ng/ml. In Trial 2, each of 54 pyometritic cows was paired with a control cow on the basis of days post partum (18-50 days). Mean concentration of progesterone was 9.7 +/- 1.0 ng/ml for the pyometritic cows and 5.7 +/- 0.8 ng/ml in control cows (P<0.005). Progesterone concentration was greater (P<0.005) in both groups of cows with palpable corpora lutea (CLs). Ninety-six percent of the pyometritic cows had palpable CLs compared to 57% of the control group. Comparing serum progesterone only in cows with a palpable CL, the mean concentration was still greater (P<0.005) in the pyometritic group (10.6 +/- 1.0 ng/ml) than the control group (6.6 +/- 1.0 ng/ml). Compatability of rectal palpation findings and concentrations of serum progesterone were 92.6% for the pyometritic group and 72.2% for the control group. Progesterone concentration increased (P<0.05) by increased days post partum in Trial 2 (n=54) but not in Trial 1 (n=23). In both Trials 1 and 2, uterine size due to pyometra increased (P<0.05) with increased days post partum. No other associations were found.     

Concentrations of progesterone in milk as a monitor of early pregnancy diagnosis in dairy cows

The objectives of the experiment were to evaluate the efficacy of using progesterone concentrations in milk and palpation per rectum on days 21 or 22 postbreeding to estimate pregnancy and evaluate management practices; and to investigate physiological occurrences leading to incorrect diagnosis of pregnancy when serial samples of milk were collected. Of particular interest were indications of early embyronic death and insemination of cows not in estrus. Milk samples were collected at the afternoon milking of days 0 or 1 (day 0 = day of estrus), 9 or 10, 21 or 22 and 27 or 28 following breeding in 200 lactating dairy cows. Tentative diagnosis of pregnancy was made based on concentrations of progesterone in milk on days 21 and 22 alone and on days 21 or 22 and 27 or 28. In addition all cows were palpated per rectum on days 21 or 22 postbreeding and a tentative pregnancy diagnosis was made. Pregnancy was confirmed by examination of the genital tract per rectum between 35 and 50 days after breeding. Values of 4 ng/ml or greater and/or the presence of a mature corpus luteum were considered positive signs of pregnancy. Progesterone in milk ranged from 0.1 to 18 ng/ml. On days 0 or 1, 9 or 10, 21 or 22 and 27 or 28 concentrations of progesterone in milk averaged 1.5 +/- 0.3, 11.1 +/- 0.5, 12.0 +/- 0.4 12.5 +/- 0.5 ng/ml for pregnant cows. Corresponding samples from nonpregnant cows averaged 1.2 +/- 0.2, 10.3 +/- 0.4, 3.0 +/- 0.4, 6.8 +/- 0.6 ng/ml, respectively. Ninety-six and 104 cows were classified as pregnant and nonpregnant on days 21 or 22 as compared to 78 and 118 cows diagnosed as pregnant and nonpregnant on days 21 or 22 and 27 or 28 combined. Pregnancy detection by progesterone in milk on days 21 or 22 with pregnancy determined via rectal palpation 35 to 50 days postbreeding was 77 and 100% accurate for positive and negative diagnosis, respectively. The percent agreement using progesterone in milk on days 21 or 22 and 27 or 28 combined was 95 and 100%, respectively, for positive and negative diagnosis. Diagnosis based on rectal palpation 21 or 22 days postbreeding was 63 92 (69%) and 76 88 (87%) for pregnant and nonpregnant cows, respectively. Ten of the 200 cows had progesterone concentratins in milk of > 4 ng/ml at the time of breeding. Six of these cows were pregnant from a previous insemination. The other four cows were nonpregnant and were inseminated during the luteal phase of the cycle. In conclusion, measurement of progesterone in milk is a useful tool in early detection of pregnant and nonpregnant cows and may be useful in detecting reproductive problems in a dairy herd. It will probably be most useful when used in combination with later pregnancy diagnosis per rectum .     

Plasma progesterone levels during the estrous cycle of Holstein and Brahman cows, Carora type and cross-bred heifers

Daily plasma progesterone (P(4)) was determined during one estrous cycle of 19 cows and 18 heifers of four different breeds: Holstein (H), Brahman (B), Carora-type (C) and crossbred (CB) females. Estrus detection was made by visual observation and using a teaser bull with a chin-ball marker. The P(4) profiles showed no differences among groups. In Group 1 (H), P(4) levels ranged from 0.5 ng/ml plasma on the day of estrus (Day 0) to 5.1 ng/ml at the luteal phase peak (Day 13). In Group 2 (B), P(4) levels ranged from 0.5 ng/ml on Day 0 to 9.2 ng/ml on Day 13. In Groups 3 (C) and 4 (CB), P(4) levels ranged from 0.5 ng/ml, on Day 0, to 13.7 ng/ml on Day 12 and 8.8 ng/ml on Day 13. These last two groups were moved to the same location and then compared. It was found that P(4) concentrations were significantly higher (P < 0.025) in Group 3 between Days 7 and 14 of the estrous cycle. In all groups, P(4) levels were lower than 1 ng/ml one day before the next estrus, and levels of 0.4, 0.5, 0.4 and 0.4 ng/ml were obtained the day of estrus in Groups 1 to 4, respectively. Results indicated that the pattern of P(4) for each one of the groups was similar to those reported by other investigators.     

Repeatability of blood serum progesterone levels in dairy heifers on day 7 of the estrous cycle

Thirty normally cycling dairy heifers were used to determine the repeatability of blood serum progesterone levels on Day 7 ± 0.25 d of the estrous cycle. The experimental group consisted of 16 Holsteins and 14 dairy crossbreds ranging in age from 18 to 24 months. Day of the estrous cycle was determined from twice daily observations for standing heat (Day 0). Serum progesterone levels for Day 7 ± 0.25 d were determined by radioimmunoassay from blood samples collected by jugular venipuncture over three to four consecutive estrous cycles. Levels of blood serum progesterone for Day 7 ± 0.25 d ranged from 0.57 to 6.03 ng/ml. Least square means for the Holstein (2.74 ng/ml) and dairy crossbred (3.38 ng/ml) groups were different (P<0.006). The repeatability for levels of blood serum progesterone on Day 7 of the estrous cycle was low (0.0115).     

Post partum ovarian activity and uterine involution in the suckled swamp buffalo (Bubalus bubalis)

Ovarian activity and uterine involution were monitored by rectal palpation, oestrus detection and plasma progesterone analysis from 3 to 4 days to approximately 150 days post partum in 38 suckled swamp buffaloes (Bubalus bubalis). The intervals from parturition to regression of the corpus luteum (CL) of pregnancy and involution of the uterus were 10 and 28 ± 6 (S.D.) days respectively. First detected oestrus and first elevation of plasma progesterone (> 0.7 ng/ml) occurred at 88 ± 26 and 96 ± 22 days in 8 and 12 buffaloes respectively. During the first 150 days post partum, 26 of 38 suckling buffaloes (68%) were acyclic (anoestrus) and of 12 animals (32%) exhibiting ovarian cycles, 4 were not detected in oestrus. The tentative diagnosis, based on rectal palpation, that CL were present between days 30 and 90 after parturition (without concurrent luteal levels of progesterone in plasma) suggests that confirmation should be by laparoscopy. It is concluded that a delay in the resumption of ovarian cyclicity post partum represents an important factor contributing to the prolonged calving to conception interval in the suckled swamp buffalo.     

Levels of prostaglandin F (PGF) in bovine endometrium uterine venous, ovarian arterial and jugular plasma during the estrous cycle (38789).

Prostaglandins F (PGF) were measured in uterine vein, ovarian artery, and jugular vein plasma and in the endometrial tissues at various times during the bovine estrous cycle, and were compared to peripheral plasma progesterone levels. Four groups of heifers at days 1-5, 10-14, 15-17 and 20-0 of the estrous cycle were studied. Low levels of PGF (48 plus or minus 12 ng/g dry tissue were measured in the endometrium on days 1-14 of the cycle. Higher values (131 plus or minus 9.0) were found at days 15 until the day of estrus (p less than 0.001). Similarly, very low levels of PGF were observed in the uterine vein plasma at days 1-14 (0.162) plus or minus 0.044) ng/mlM plus or minus S.E.), whereas on days 15 until the day of estrus the levels ranged from 1.5 to 3.0 ng/ml. The increases in uterine vein PGF on day 15 occurred even while peripheral plasma progesterone levels were still high. However, PGF was not elevated in either the ovarian artery or the jugular vein at any time during the cycle, even when uterine vein levels were greatly elevated. No differences in PGF content were detected in endometrial tissue from uterine horns adjacent or opposite to the functional corpus luteum.     

Relationship between plasma progesterone concentrations and pregnancy rates in cattle receiving either fresh or previously frozen embryos

Blood samples were collected for the measurement of progesterone concentrations from 320 Holstein-Friesian heifers on Days 7 and 21 post-estrus. All animals were the recipients of either a fresh or previously frozen embryo on Day 7 and were palpated for pregnancy on Day 60 post-estrus. At the time of transer, progesterone levels were highly variable and were not strongly related to subsequent pregnancy status. There was a tendency for lower pregnancy rates in heifers receiving fresh embryos if progesterone levels were less than 1 ng/ml (33 vs 64% overall), and for previously frozen embryos when progesterone concentrations were less than 3 ng/ml (34 vs 44% overall). Progesterone concentrations were not related to subjective evaluation of corpus luteum quality by palpation per rectum. No heifers which maintained pregnancy had progesterone levels less than 1 ng/ml on Day 21. Only 41% of 247 heifers receiving either fresh or previously frozen embryos that were not pregnant on Day 60 had progesterone concentrations less than 1 ng/ml on Day 21. These data suggest that many recipients that do not maintain a pregnancy will experience an extended estrous cycle after transfer.     

Effect of PGF-2 alpha on serum progesterone levels in the swamp buffalo (Bubalus bubalis)

Induction of some oestrous phenomena was achieved. Treatment with 25 mg PGF-2 alpha cuased mucous discharge, within 48-72 h after injection, which lasted for 4-5 days. Rectal palpation indicated rapid regression of the CL, and in 9 treatments of 6 buffaloes serum progesterone levels declined from 1.76 +/- 0.01 (s.d.) ng/ml before treatment to less than 0.25 ng/ml within 24 h after injection. Concentrations increased at about Day 11 and reached a peak of 1.78 +/- 0.62 ng/ml on Day 18.50 +/- 2.45.     

Do high progesterone concentrations decrease pregnancy rates in embryo recipients synchronized with PGF2alpha and eCG?

The objective of this study was to evaluate the effects of equine chorionic gonadotropin (eCG) treatment on the number of induced accessory corpora lutea (CL), plasma progesterone concentrations and pregnancy rate in cross-bred heifers after transfer of frozen-thawed (1.5M ethylene glycol) embryos. All recipients received 500 microg PGF2alpha (dl-cloprostenol, i.m.) at random stages of the estrous cycle (Day 0) and were observed for estrus for 7 days. On Day 14, heifers detected in estrus between 2 and 7 days after PGF2alpha treatment were randomly allocated to four groups ( n=83 per group) and given 0 (control), 200, 400, or 600 IU of eCG. Two days later (Day 16), these recipients were given PGF2alpha and observed for estrus. Six to eight days after detection of estrus, plasma samples were collected to determine progesterone concentration and ultrasonography was performed to observe ovarian structures. Heifers with multiple CL or a single CL >15 mm in diameter received an embryo by direct transfer. Embryos of excellent and good quality were thawed and transferred to the recipients by the same veterinarian. Pregnancy was diagnosed by ultrasonography and confirmed by transrectal palpation 21 and 83 days after embryo transfer (ET), respectively. Plasma progesterone concentrations on the day of transfer (Day 7 of the estrous cycle) were 3.9+/-0.7, 4.2+/-0.4,6.0+/-0.4 and 7.8+/-0.6 ng/ml for groups Control, 200, 400, and 600, respectively (Control versus treated groups P=0.009; 200 versus 400 and 600 groups P=0.0001; and 400 versus 600 P=0.012 ). Conception rates 83 days after ET were 41.9, 50.0, 25.0, and 20.9% for groups Control, 200, 400, and 600, respectively (200 versus 400 and 600 groups P=0.0036 ). In conclusion, an increase in progesterone concentration, induced by eCG treatment, did not improve pregnancy rates in ET recipients. Conversely, there was a decline in conception rates in the animals with the highest plasma progesterone concentrations.     

Comparison of ovarian palpation, milk progesterone and plasma progesterone in the cow

Holstein cows were examined twice weekly, beginning at 13 to 18 days after parturition, using palpation per rectum and milk progesterone (P4) assay to determine the functional status of the corpus luteum (CL). These results were then compared with P4 concentrations in the plasma to determine which test was the more accurate in detecting functional luteal tissue, or if both tests were needed for optimal accuracy. The tests were found to be comparable except when the plasma P4 concentration was <1. 0 ng/ml. At this level, errors due to palpation occurred more frequently than those due to milk P4 concentrations since the still palpable CL of pregnancy could be mistaken for a functional CL at 14 to 21 days after parturition. However, at all the other concentrations including when plasma P4 was <1.0 ng/ml and the cows were more than 21 days post partum, neither the milk P4 assay nor palpation per rectum could be considered the better indicator of luteal status. Therefore, we conclude that the combined use of both tests does not afford better assessment of luteal function than either test alone.     

Induction of luteal activity and progesterone secretion in the nonpregnant one-humped camel (Camelus dromedarius)

Corpora lutea (n = 20) were detected in 5 one-humped female camels studied during a period of 4 months. Complete mating by a vasectomized male, male introduction into the pen of females without mating, or a progesterone decrease from a previous corpus luteum were followed by a similar progesterone pattern. A maximal plasma concentration of 4.5 +/- 1.5 ng progesterone/ml (2.7-8.8 ng/ml) occurred 8.55 +/- 1.32 days (6-11 days) after the inducing stimulus. Luteal regression, beginning 8.65 +/- 1.18 days after the stimulus, was completed at Day 11.55 +/- 1.05. Morphological development of ovarian structures, detected by rectal palpation, was in synchrony with the progesterone increase, but there was a prolonged period of regression. Females accepted mating up to 7 days after the ovulatory stimulus, when progesterone levels were as high as 3.5 ng/ml. This study establishes the absence of pseudopregnancy in the one-humped female camel, and offers opportunities for improving the management of reproduction. It also shows that ovulatory stimuli other than mating can be effective in these animals.     

Pregnancy rates relative to recipient plasma progesterone levels on the day of nonsurgical transfer of frozen/thawed bovine embryos

A total of 71 synchronized dairy heifers (Holstein Friesian x German Black Pied) were used as recipients of seven-day old frozen/thawed bovine embryos. Plasma progesterone concentrations and corpus luteum quality on the day of nonsurgical transfer (= day 7) were determined and related to pregnancy rates or estrus intervals in nonpregnant recipients. A total of 32 recipients (45.1 %) maintained pregnancy; 39 recipients (54.9 %) did not. No significant differences could be detected between progesterone levels in recipients that remained pregnant (3.14 +/- 0.24 ng/ml; x +/- SEM ) and those that did not maintain pregnancy (3.23 +/- 0.28 ng/ml). Optimal progesterone levels were between 2 and 5 ng/ml coinciding with a pregnancy rate of 51.1 % (24 47 ). Pregnancy rates apparently were decreased when progesterone levels were below 2 ng/ml (35.3 %; 6 17 ) or above 5 ng/ml (28.6 %; 2 7 ). Hence, optimal progesterone levels were identical to those for freshly collected embryos reported previously by Remsen et al. (1). Bovine corpus luteum quality graded by rectal palpation was related to some extent to progesterone levels but not to pregnancy rates. Out of 39 nonpregnant recipients seven animals (17.9 %) with a mean plasma progesterone level of 3.76 +/- 0.72 ng/ml showed an extended estrus interval of more than 55 days, probably indicating early embryonic mortality. Progesterone levels did not significantly differ between nonpregnant recipients with estrus intervals of various length. Plasma progesterone levels at the time of transfer are of limited diagnostic value for screening recipients prior to transfer of frozen/thawed embryos.     

Effect of repeated laparoscopic surgery on the bovine estrous cycle

The effects of repeated laparoscopic surgery on the length of the bovine estrous cycle, estrus, ovulation and corpus luteum function were determined after one estrous cycle of normal duration (18 to 24 days). Five, Angus x Hereford cows were subjected to laparoscopy on days 5, 13, 18 and 20 (estrus = day 0) of the subsequent cycle. Blood was collected daily during the cycle in which laparoscopy was performed (surgical cycle) and during the next cycle (postsurgical cycle). Lengths of the surgical and postsurgical cycles (22.3 +/- .5 days and 21.5 +/- .6 days, respectively) did not differ (P>.05) from that of the presurgical cycle (21.8 +/- .2 days). Average concentrations (ng/ml) of LH and progesterone in serum were similar during the surgical and postsurgical cycles (1.2 +/- .1, 2.2 +/- .2 vs 1.3 +/- .2 and 2.3 +/- .1). Progesterone concentrations remained above 1 ng/ml for 17 and 16 days during the surgical and postsurgical cycles, respectively. A pre-ovulatory rise in LH, along with estrus and ovulation was confirmed in all animals. Follicular development, characterized by follicular volume, increased progressively from days 5 to 20, with the largest increase occurring between days 13 and 18. These results indicate that laparoscopy, used at the times and frequency specified, does not alter reproductive function of cyclic cows and can provide information on ovarian activity.     

Serum progesterone changes in luteal cyclicity and duration of estrous cycle in Formosan sika deer (Cervus nippon taiouanus) hinds

A study was conducted to investigate the serum progesterone (SP(4)) profiles and duration of estrous cycles in the farmed Formosan sika deer (FSD; Cervus nippon taiouanus) during the major breeding season. Five parous, open and non-milking hinds were allotted to collect peripheral blood samples twice weekly for P(4) measurement by radioimmunoassay beginning at the initiation of the rutting season indicated by rutting behaviors of the sexually mature stags. The hinds were polyestrous as proved by cyclic changes of SP4 levels. After the presumptive estrus shown by the lowest concentration of SP(4) (0.20+/-0.01 ng/ml), this ovarian hormone markedly elevated on day 7 of the cycle (1.67+/-0.11 ng/ml), reached plateau (3.15+/-0.16 ng/ml, P<0.01) during days 11 to 18, and then declined to the basal levels in the subsequent estrus. It is concluded that mean duration of the estrous cycle in FSD during the major rutting season is 19.3 days with a range of 17 to 21 days, and that the patterns of circulating progesterone profiles during the estrous cycles of the FSD are similar to those of other deer species so far investigated.     

Estrogen and progesterone concentrations in bovine milk during the estrous cycle

Estrogen and progesterone concentrations in milk during the estrous cycle were estimated in 18 normally cycling Holstein dairy cows. The estrogen and progesterone concentrations in milk during the estrous cycle followed the pattern described for them in blood in the corresponding period. During most of the estrous cycle, estrogen concentration remained at approximately 200 pg/ml and reached a proestrous peak of 360 +/- 127 pg/ml on day 19. The progesterone concentration in milk during the estrous cycle increased to a peak on day 13 (45.5 +/- 6.6 ng/ml) and thereafter declined towards estrus. Estrus detection/prediction based on milk progesterone concentrations appears feasible in view of the significant differences in milk progesterone concentrations between the early luteal (post-ovulatory), luteal and rapid follicular growth periods of the estrous cycle.     

Uterine involution and postpartum ovarian activity in Nili-Ravi buffaloes

Uterine involution and postpartum ovarian activity were studied in 53 Nili-Ravi buffaloes. Mean intervals to uterine involution (26 days), regression of the corpus albicans of pregnancy (22 days), resumption of follicular activity (21 days) and first postpartum estrus (56 days) were not affected by the month of calving or age. Mean interval to formation of first corpus luteum (CL) after calving as indicated by progesterone in plasma (>/= 1.5 ng/ml) was 23.8 +/- 1.7 days, but only 52% of these CL were palpable. The number of CL formed before first postpartum estrus ranged from zero to five per buffalo; mean values based upon progesterone and palpation were 1.6 +/- 1.3 and 0.8 +/- 0.2, respectively. Based upon either progesterone or palpation, length of first postpartum luteal phase (7.9 or 6.6 days) was shorter than the luteal phase immediately preceeding the first estrus (12.1 or 8.9 days). Intervals from regular cyclic ovarian activity was not established until first estrus and intervals from the end of one luteal phase to the onset of the next were as long as three weeks. High concentrations of progesterone (>/= 1.5 ng/ml) on the day of behavioral estrus were seen in 23% of the buffaloes studied.     

Manipulation of estrous cycle in dwarf goat (Capra hircus) using estrumate under different management conditions

A study was conducted to elucidate the effectiveness of exogenous estrumate (prostaglandin F(2alpha)) treatment as a synchronizing agent for Dwarf goats and to establish the progesterone levels at different reproductive stages under two different environmental and nutritional conditions. Female Dwarf goats of various ages were raised, 10 each at two sites, viz. the Bio-Saline Research Substation (BSRS), Lahore and at the Nuclear Institute for Agriculture and Biology (NIAB), Faisalabad. The animals at the NIAB farm were reared on non-saline soil under normal grazing conditions, while the other animal lot was raised on salt-affected lands at the BSRS, Lahore and was fed on non-conventional fodders produced by salt-affected lands. The animals received two intramuscular doses (0.5 ml each) of estrumate (125 microg/ml) at 10 days interval. Nineteen of the 20 animals exhibited estrus after 56-72 h of the second injection of estrumate. The mean progesterone concentration in the NIAB and BSRS lots was 2.8 and 2.4 ng/ml, respectively, at the time of second injection and declined to the basal level (estrus) within 48 h. A gradual increase in the progesterone level occurred during the metestrus, reaching maximum during the luteal phase when it was 6.3 and 6.7 ng/ml in NIAB-lot and BSRS-lot, respectively. During the proestrous phase, the progesterone level decreased to the basal level (0.1 ng/ml) at the onset of the next estrus after 22 days. The length of the induced or natural estrous cycle (20+/-1 days) was not affected by the estrumate treatment, nor by the environmental and nutritional conditions. Breeding was allowed after the natural estrous cycle at the onset of third estrus and a high fertility rate (95%) was achieved. The progesterone concentrations remained at higher level (4.5-9.4 ng/ml) throughout the gestation period, declined gradually in the prepartum period, and dropped to the basal level at the completion of parturition. The results suggested that estrumate is an efficient synchronizing agent for the Dwarf goats kept under different environmental-nutritive conditions and that the progesterone profile is a useful indicator to assess the reproductive status of the goats.     

The influence of the corpus luteum on ovarian follicular dynamics during estrous synchronization in goats

Ovarian follicular dynamics and fertility are unaffected by the presence or absence of a corpus luteum during synchronization of estrus with progestins in goats. On day 5 of the estrous cycle (estrus= day 0), a gestagen-containing sponge was inserted in the vagina for 11 days. To remove corpora lutea, one group of goats (CL-, n=41) received 7.5 mg of luprostiol on days 7 and 8 of the estrous cycle. The second group of goats retained the CL (CL+, n=38). Growth and development of follicles > or =4 mm in diameter were measured daily from onset of estrus to 2 days after subsequent ovulation in seven goats from each group, using rectal ultrasonography. Estrus was detected by the use of a reproductively sterilized buck and estrous does were subsequently mated. The number of waves of follicular development (CL- =3.57+/-0.2 versus CL+ =3.14+/-0.14; P>0.05) did not differ between groups. The second wave of follicular development was present at the time of progesterone decline in the CL- group and neither its duration (CL- =4.8+/-0.4 versus CL+=5.6+/-0.7 days; P>0.05) nor the day of commencement of the third wave of follicular development (CL -=11.6+/-0.7 versus CL+=11.8+/-0.6; P>0.05) were altered by the concentration of endogenous progesterone. The pregnancy rate was similar between the two groups. (CL-=68.29% versus CL+=65.79%; P>0.05). Thus, in goats, ovarian follicular dynamics and fertility were not altered by the presence or absence of a corpus luteum during estrous synchronization.     

Characteristics of the oestrous cycle of Iberian red deer (Cervus elaphus hispanicus) assessed by progesterone profiles

This study examines the length of the oestrous cycle in 16 Iberian red deer females assessed by means of changes in progesterone concentrations, along with the changes in the profile of this hormone. Samples were collected three occasions per week from the week after calving (15 May to 15 June) up to May of the following year. The oestrous cycle lasted 19.57+/-0.29 days (range 10-27 d) calculated in 130 oestrous cycles examined. Progesterone titres did not rise above 0.5 ng/ml in the follicular phase, except in four samples. The maximum peak in progesterone concentration during the luteal phase remained above 1 ng/ml in most cases. Twenty-five percent of the individuals studied (4 out of 16) showed an oestrous cycle lasting shorter than the mean (15.2+/-0.30 days) before the start of the reproductive season, followed by a period of sexual inactivity. The standard progesterone profile in natural oestrous cycles rose from basal levels to those above 0.5 ng/ml four days after onset of oestrus, reached a peak of 1.71+/-0.07 ng/ml and then declined to less than 0.2 ng/ml after day 20. Following the rapid decline of progesterone after day 14, the concentration remained around the baseline level of 0.1 to 0.2 ng/ml during the immediate pre- and post-ovulatory phase of the cycle.