Influence of perioestrous suprabasal progesterone levels on cycle length,oestrous behaviour and ovulation in heifers

In order to induce suprabasal plasma concentrations of progesterone after luteolysis and to determine their effect on oestrous behaviour and ovulation, heifers subcutaneously received silicone implants containing 2.5 (n = 4), 5 (n = 4), 6 (n = 3), 7.5 (n = 3) or 10 (n = 4) g of progesterone, or an empty implant (controls, n = 5) between days 8 and 25 of the cycle (ovulation designated Day 0). Growth of dominant follicles and time of ovulation were determined by ultrasound, and signs of oestrus were recorded and scored. Blood was collected at 2–4 h intervals from Days 15 to 27 and assayed for progesterone concentration. In all heifers, plasma concentrations of progesterone sharply decreased during Days 16–18. Control heifers had their lowest progesterone levels on Days 20.5 and 21, standing oestrus on Day 19.5 ± 0.4 (mean ± SEM), and ovulated on Day 20.7 ± 0.4. A similar pattern was observed in heifers treated with 2.5 and 5 g progesterone. Heifers treated with 6, 7.5 and 10 g of progesterone showed an extended (P < 0.05) interovulatory interval. Onset of prooestrus and time of maximum expression of signs of oestrus were not significantly different from those in controls. However, there was an absence of standing oestrus in most of the cases, signs of oestrus lasted longer (P < 0.05) and were weaker in intensity when doses increased. In these groups, the lowest progesterone concentrations were attained shortly after implant removal. Some heifers treated with 6 and 7.5 g of progesterone had standing oestrus and post oestrous bleeding as seen in the controls but ovulation occurred from Days 24.5 to 27. When plasma progesterone concentrations were over 1 nmol 1⁻¹, disturbed oestrus and delayed ovulation occurred. The extended period of prooestrus and oestrus and delayed ovulation were similar to that described in cases of repeat breeding. It is suggested that suprabasal plasma concentrations of progesterone, after luteolysis, may lead to asynchrony between onset of oestrus and ovulation and consequently be a cause of repeat breeding in cattle.     

Effect of induced suprabasal progesterone levels around estrus on plasma concentrations of progesterone, estradiol-17beta and LH in heifers

A controlled study was carried out to investigate the effects of suprabasal plasma progesterone concentrations on blood plasma patterns of progesterone, LH and estradiol-17beta around estrus. Heifers were assigned to receive subcutaneous silicone implants containing 2.5 g (n=4), 5 g (n=4), 6 g (n=3), 7.5 g (n=3) or 10 g (n=4) of progesterone, or implants without hormone (controls, n=5). The implants were inserted on Day 8 of the cycle (Day 0=ovulation) and left in place for 17 d. The time of ovulation was determined by ultrasound scanning. Blood was collected daily from Days 0 to 14 and at 2 to 4-h intervals from Days 15 to 27. Control heifers had the lowest progesterone concentrations on Days 20.5 to 21 (0.5 +/- 0.1 nmol L(-1)); a similar pattern was observed in heifers treated with 2.5 and 5 g of progesterone. In the same period, mean progesterone concentrations in the heifers treated with 6, 7.5 and 10 g were larger (P < 0.05) than in the controls, remaining between 1 and 2.4 nmol L(-1) until implant removal. A preovulatory estradiol increase started on Days 16.4 to 18.4 in all the animals. In the controls and in heifers treated with 2.5 and 5 g of progesterone, estradiol peaked and was followed by the onset of an LH surge. In the remaining treatments, estradiol release was prolonged and increased (P < 0.05), while the LH peak was delayed (P < 0.05) until the end of the increase in estradiol concentration. The estrous cycle was consequently extended (P < 0.05). In all heifers, onset of the LH surge occurred when progesterone reached 0.4 to 1.2 nmol L(-1). The induction of suprabasal levels of progesterone after spontaneous luteolysis caused endocrine asynchronies similar to those observed in cases of repeat breeding. It is suggested that suprabasal concentrations of progesterone around estrus may be a cause of disturbances oestrus/ovulation.     

Pregnancy rates relating to plasma progesterone levels in recipient heifers at day of transfer

A group of Holstein heifers (n=223), weighing approximately 454 kg, were used to determine pregnancy rates in relation to plasma progesterone concentrations in recipients on the day of embryo transfer. All recipients were in estrus within +/- 12 hours of the donor cows. These data showed a cubic trend by regression analysis. Chi-square test revealed that there was a significant (P<0.0001) relationship between plasma progesterone concentrations and resulting pregnancies. Pregnancy rates were low when plasma progesterone concentrations were below 2.00 ng/ml. Actual number of pregnancies relating to specific plasma progesterone groups were 12 61 (20%) for <2.00 ng/ml, 94 127 (74%) for concentrations between 2.00 and 5.00 ng/ml, and 21 35 (60%) for >5.00 ng/ml. Corpora lutea were classified as good, poor, or cystic by both manual and visual observation. These observations revealed that manual palpation of the corpus luteum was not a valid criterion of the corpus luteum function as measured by plasma progesterone concentrations. Further observation revealed no significant relationship between plasma progesterone and whether the corpus luteum was on the left or right ovary. Hence, pregnancy rate was not significantly associated with the left or right ovary. Pregnancies were determined by rectal palpation at 60 days.     

Studies on oestrous symptoms of buffalo heifers

Studies based on frequent daily observations for nine months, encompassing 92 oestrous periods in 31 Murrah buffalo heifers, revealed that the vulval discharge of clear mucus in varying quantities in a recumbent animal, even in silent heat, was the most reliable single sign of heat in buffalo heifers. Of the other signs observed, wall walking (segregation) and bellowing confirmed oestrus in 83.69% and 80.43%, respectively, while placid response of the animal to the placing of palm of hand on the rump ano response to light massage of vulval lips were seen in 86.95% and 83.69%, respectively. Based upon the degree of manifestation of oestrous symptoms, intensity of oestrus was divided into four categories. Four daily observations of the animal for important symptoms of heat a few days before the expected oestrus could make oestrous detection a sure success.     

Effect of low levels of exogenous progesterone on puberty in beef heifers

Twenty eight prepuberal Charolais-Angus cross heifers approximately 15 months old and averaging 334 kg were implanted intravaginally with either a placebo (control, 9 heifers) or progesterone containing implant (treated, 19 heifers). Implants were left in place 3 days. Seventeen heifers (8 controls and 9 treated) retained implants. Plasma progesterone concentrations were < .4 ng/ml in control heifers and 1.5 +/- .59 ng/ml in treated heifers while implants were in place. Seven heifers, all in the treated group, were observed in estrus within 4 days after implant removal. All but one heifer observed in estrus had elevated plasma progesterone concentrations 12 days after implant removal. None of the heifers not observed in estrus had elevated progesterone levels at this time. This study indicates that low levels of exogenous progesterone (1 to 2 ng/ml plasma for 3 days) will induce estrus in prepuberal heifers following its withdrawal.     

Ovarian response to hCG treatment during the oestrous cycle in heifers

The aims of this study were to investigate whether treatment with a single ovulatory dose of hCG, between the day of oestrus and the end of the luteal phase, could induce extra ovulations in heifers and whether the presence of an existing corpus luteum (CL) affected the response. Heifers (N = 32) were injected with 1500 i.u. hCG or saline on a given day of the oestrous cycle. Treatments were repeated during subsequent cycles to provide a total of 71 observations, 57 of which followed an injection of hCG, given between Day 0 (oestrus) and Day 16, and 14 of which followed saline injections as controls. Ovulatory responses were noted by laparoscopy 2 days after hCG treatment. No heifers injected with saline produced additional CL. Of the hCG-treated cycles, 23 resulted in the formation of an additional CL, and this was significantly affected by the stage of the oestrous cycle when hCG was given; a greater response was observed during the early (Days 4-7) and late (Days 14-16) stages of the luteal phase than at the mid-luteal phase of the oestrous cycle. Two heifers were also treated with hCG on Days 17 or 18 of the oestrous cycle, but before oestrus; both had induced CL. There were no significant differences between the left-right orientation of the existing CL or the hCG-induced CL. These results demonstrate that the large, luteal-phase follicle of the cow is capable of ovulating in response to hCG and that the induced CL is not affected by the presence of an existing CL.     

Reproductive performance of prepubertal Bos indicus heifers after progesterone-based treatments

The objective was to evaluate the effects of exogenous progesterone (P4) on reproductive performance of prepubertal Bos indicus heifers. Prepubertal Nelore heifers (n = 589; 24.0 ± 1.13 mo; 298.0 ± 1.89 kg; body condition score of 3.2 ± 0.26; mean ± SEM) were randomly assigned to receive, between experimental Days −12 and 0: no treatments (CIDR0; n = 113); a new intravaginal insert (CIDR) containing 1.9 g of P4 (CIDR1; n = 237); or a similar insert previously used three times, with each use occurring for 9 d (CIDR4; n = 239). An additional treatment group was pubertal heifers given 12.5 mg dinoprost tromethamine im on Day 0 (PGF; n = 346), and used as controls for evaluation of conception rates. On Day 0, transrectal palpation was done for uterine score evaluation (UtS; 1-3 scale), blood samples were taken for serum P4 concentrations, and follicle diameter (FD) was measured. The breeding season started on Day 1 and consisted of AI after detection of estrus between Days 1 and 45, and exposure to bulls between Days 46 and 90. There were effects of treatment (P < 0.05) on serum concentrations of P4 on Day 0 (0.37 ± 0.16, 2.31 ± 0.11, and 1.20 ± 0.11 ng/mL for CIDR0, CIDR1, and CIDR4, respectively; mean ± SEM), FD on Day 0 (9.45 ± 0.24, 9.72 ± 0.17, and 11.42 ± 0.16 mm), UtS on Day 0 (1.49 ± 0.06, 1.88 ± 0.04, and 2.24 ± 0.04), estrus detection rates at 7 d (19.5, 42.6, and 38.3%) and 45 d (52.2, 72.1, and 75.3%) of the breeding season, and on pregnancy rates at 7 d (5.3, 14.3, and 18.4%), 45 d (27.4, 39.2, and 47.7%) and 90 d (72.6, 83.5, and 83.7%) of the breeding season. Conception rate 7 d after the start of the breeding season was greater (P < 0.05) in heifers from the CIDR4 (46.8%) and PGF (43.8%) groups than in the CIDR0 (27.3%) and CIDR1 (33.7%) groups. In conclusion, exogenous P4 hastened puberty and improved pregnancy rates at the beginning of the breeding season in prepubertal Bos indicus heifers. Furthermore, previously used CIDR inserts were better than new inserts.     

Peripheral progesterone levels in pregnant and non-pregnant heifers following use of HCG.

Progesterone concentration in jugular blood of bred beef heifers was determined on days 9 and 16 in two trials. Human chorionic gonadotrophin (HCG) was administered to some of the heifers in each trial in an attempt to improve pregnancy percentage.In Trial 1, 183 heifers were divided into a control group and three groups of animals which were subjected to a 9-day estrous synchronization treatment prior to breeding. The treatment consisted of an ear implant containing 17 α acetoxy-11-beta-methyl 17 nor preg 4-ene 3, 20 dione (norgestomet) left in place for 9 days and an injection of 5 mg estradiol valerate (EV) and 3 mg of norgestomet given at the time of implantation. The heifers in one group received .25 mg estradiol-17β at time of implant removal; heifers in the 2nd group received 1500 IU of HCG in 5% beeswax and 95% sesame oil at breeding time, while heifers in the 3rd group received a placebo injection containing 5% beeswax and 95% sesame oil at breeding time. No differences in serum levels of progesterone were observed (P>0.5) between treatments or between pregnant and non-pregnant heifers on day 9 or 16 (P>.05). Pregnancy percentage in heifers receiving HCG was similar to that noted in the control heifers or the placebo injected heifers while injection of estradiol 17β decreased the proportion of heifers which became pregnant.In trial 2, 58 heifers which had been bred 1 or 2 times without becoming pregnant were divided into a control group and a group in which heifers received 1000 IU of HCG 96 hr. after observed estrus. In heifers receiving HCG, serum levels of progesterone were higher (P<.01), on day 9 and 16 post estrus than in controls but no difference in serum progesterone was noted (P>.05) between pregnant and non-pregnant heifers on day 9 or 16. The proportion pregnant did not differ (P>.05) between heifers receiving HCG and control heifers.     

Effect of ACTH-challenge on progesterone and cortisol levels in ovariectomised repeat breeder heifers

In order to investigate the potential influence of stress as a component of the repeat breeding syndrome, the adrenocortical capacity for steroid production was evaluated in ovariectomised dairy heifers. In repeat breeder heifers (RBH), marginally elevated plasma progesterone levels during oestrus, so-called suprabasal progesterone levels, have earlier been measured and are believed to impair fertility. The aim was to distinguish if this progesterone could be of extra-gonadal or in this case, adrenal origin. Baseline levels of plasma cortisol and progesterone were determined as well as the corresponding response after induced acute stress in the form of an adrenocorticotropin (ACTH)-challenge. Comparisons were made between strictly selected RBH, n=5 and virgin heifers (VH), n=5 of the Swedish Red and White breed. The heifers were used as their own pre-challenge controls in a 2-day trial. On the control day, saline was injected i.v. and on the treatment day, a synthetic analogue of ACTH (60 microg Synachten(R)). Via a jugular vein catheter, blood samples were collected every 30 min for 6 h each day of the experiment. Analyses for plasma progesterone and cortisol were made. RBH had a significantly higher (P<0.01) pretreatment baseline cortisol level (10.1+/-2.3 nmol l(-1)) than VH (2.6+/-0.2 nmol l(-1)). Moreover, the cortisol response after stimuli was stronger in RBH than VH, especially concerning total hormone production (P<0. 001), but there was also a tendency towards higher peak values (P=0. 06) and longer duration of significantly increased hormone concentrations (P=0.08). Progesterone concentrations, however, did not differ between the groups. Both baseline levels (P=0.25) and posttreatment production (P=0.45) were of the same magnitude in RBH and VH. In conclusion, the study could not confirm that suprabasal progesterone concentrations during oestrus in RBH derive from the adrenal glands. Still, apparent differences were found in adrenocortical activity when ovariectomised heifers, VH and RBH, were subjected to an ACTH-challenge. It is suggested that a sustained adrenal stimulation associated with environmental or social stress could be one factor in the repeat breeding syndrome.     

Embryo yield and plasma progesterone profiles in superovulated dairy cows and heifers.

This study was conducted to compare the superovulatory (SOV) response of dairy cows (n=172) and heifers (n=172), with two SOV treatments started at the mid-luteal-phase of the estrus cycle. Donors were randomly treated either with equine chorionic gonadotrophin (eCG) plus neutra-eCG serum (eCG+N group, n=167) or follicle stimulating gonadotrophin (FSH-P group, n=177).No significant differences were observed among groups in the percentage of superovulatory responsive donors (SR donors; corpora lutea (CL) >/=2), the mean number of total ova, fertilized ova and viable embryos recovered. Cows yielded significantly less total ova and less fertilized ova (P<0.05) and tended to yield less viable embryos (P<0.06) than heifers.Plasma progesterone (P4) concentrations (n=135 donors) on the day of PGF(2alpha) (PGF) injection and on the day of SOV estrus were significantly higher (P<0.01) in eCG+N than in FSH-P donors and, the increase between those 2 days was also significantly higher (P<0.05) in group eCG+N than in group FSH-P, suggesting a higher luteotrophic effect of eCG than FSH-P. SR donors had P4 levels significantly higher (P<0.001) than non-SR donors only on day 5 after the SOV estrus and on the day of embryo recovery. Plasma P4 concentrations at 5 days after the SOV estrus and at embryo recovery correlated significantly (r=0.76, P<0.001).Heifers had significantly higher P4 levels than cows at gonadotrophin injection (P<0.01), PGF injection (P<0.001), 5 days (P<0.01) and 7 days (P<0.001) after the SOV estrus. At day 7 after the SOV estrus, P4 concentrations per ova recovered were significantly higher in heifers than in cows (P<0.01). The increase of plasma P4 per ova recovered, between days 5 and 7 after the SOV estrus, was significantly (P<0.01) higher in heifers than in cows. Also, the increase of plasma P4 between injections of gonadotrophin and PGF was significantly higher (P<0.05) in heifers than in cows.These results suggest that heifers have higher plasma P4 concentrations at diestrus (either before or after the SOV treatment) and this is associated with a higher embryo yield and quality, as compared to lactating cows. These higher plasma P4 concentrations reflect not only differences in ovulation rate as well as the competence of the corpus luteum, which is potentialized by gonadotrophin stimulation.     

Profiles of plasma progesterone before and at the onset of puberty in yak heifers

Sixty yak heifers were closely observed to determine their ages at sexual maturity and 15 heifers were used to analyze the plasma progesterone by radioimmunoassay before and at the attainment of puberty. Yak heifers began cyclic activity at a mean (+/-S.D.) age of 33 +/- 6.7 months, but with wild variation. Fifteen heifers used to determine plasma progesterone were divided into three age groups: group I (10-14 months, n = 5), group II (20-24 months, n = 5) and group III (30-36 months, n = 5). Group I yak heifers were found to have two progesterone profiles: inactive ovary (IO) profile and low progesterone short cycle (LPSC) profile; group II had three profiles: IO profile, LPSC profile and LPNC (low progesterone normal cycle) profile; group III had three profiles: LPSC profile, LPNC profile and a normal oestrous cycle profile. It would be concluded from the present study that one or two, or even more brief rise(s) in circulating progesterone presented in yak heifers. These rises, however, were not followed by a normal luteal phase except two yak heifers that came to heat. This characteristics found in yak was obviously different with that reported in other animals.     

Social ranking and plasma progesterone levels in goats

Progesterone is essential for maintaining pregnancy in goats, and embryonic losses may be a consequence of the reduction in circulating progesterone levels close to the time of implantation. Some evidence exists regarding social dominance affecting the plasma progesterone levels in several species—where dominant females conceive earlier. The objective of this research was to determine whether serum progesterone levels differ in goats of different social status. A behavioural study was conducted for 10 days in a herd of 57 does and an individual success index (SI) was calculated according to the result of aggressive interactions. Goats were classified as high (SI: 1–0.67), medium (SI: 0.66–0.34) and low-ranking (SI: 0.33–0.0). Ovulation was synchronized using two injections of prostaglandin 11 days apart, and the plasma progesterone levels determined daily for a period of 20 days. The area under the plasma progesterone curve during the entire study was greater in the high than in the medium and low-ranking does (96.2 ± 5.8, 79.5 ± 5.3 and 81.3 ± 5.3 ng/ml, respectively, P < 0.05). During days 11–17 following prostaglandin synchronization, the plasma progesterone levels were higher in the high-ranking (P < 0.05), compared to the low-ranking does. Plasma progesterone levels were significantly correlated with SI at days 14 and 15 (r = 0.26; P < 0.05). Results suggest a relationship between social ranking of goats and the plasma progesterone production from the corpus luteum and other possible sources.