Plasma hormone profliles and fertility in ewe lambs given progestagen supplementation after mating

Clun Forest ewe lambs (n = 124) were used to investigate the effects of post-mating progestagen supplementation on fertility. The animals were assigned to 1 of 3 three treatments: Group A (n = 41) served as the controls, Group B (n = 42) received 3 weekly injections of 6 mg of medroxyprogesterone acetate (MAP), while Group C (n = 41) was treated with intravaginal sponge containing 60 mg of MAP; all treatments were administered from Day 5 to Day 26 post mating. Supplementation did not increase the percentage of animals pregnant or those lambing: Group A, 72.2 and 66.6%; Group B, 57.5 and 50.0%; and Group C, 67.5 and 60.0%, respectively. Furthermore, there was no effect of supplementation on plasma progesterone, prolactin, cortisol, growth hormone, insulin, or glucose concentrations (P>0.05). However, pre- and post- mating hormone profiles differed significantly between the animals that lambed or aborted and the animals which were found to be barren at lambing. In the barren animals, progesterone concentrations were lower 4 days before and 9 to 33 days after mating (P<0.01), while overall prolactin concentrations were higher throughout the trial (P<0.01). But there was no difference between barren and fertile lambs in cortisol, growth hormone, insulin or glucose concentrations (P>0.05). These results indicate that progestagen supplementation does not increase the reproductive performance of ewe lambs. However, infertility is associated with reduced luteal function and increased prolactin concentration before and after mating.     

Synchronization of estrus with short- and long-term progestagen treatments and the use of GnRH prior to short-term progestagen treatment in ewes

The objective of the present study was to determine the efficacy of the synchronization of estrus using short- and long-term progestagen treatments in ewes at the onset of the breeding season, and to evaluate the effect of the exogenous GnRH administration immediately prior to short-term progestagen treatment on the reproductive performance. A total of 240 Tahirova cross-bred ewes, aged 18–24 months, and 40 rams, aged 2–4 years-old, were used in the trial. Ewes were divided equally into 3 groups (n = 80 per group). Intravaginal progestagen sponges containing FGA (30 mg) were inserted in the ewes for 7 d in the FGA1 (short-term) and GnRH treatment groups, and for 12 d in the FGA2 group (long-term). The ewes in the GnRH group received 10.5 μg busereline acetate i.m. at the time of sponge insertion. Tiaprost tromethamol (PGF_2α; 0.294 mg) and eCG (400 IU) were injected i.m. on the 6th day of progestagen treatment in the GnRH and FGA1 groups, and on the 11th day in the FGA2 group following sponge insertion. All ewes were hand-mated once at the detection of estrus. The estrous response, fertility rate, multiple birth rate and litter size recorded was 88.7, 87.3, 51.6% and 1.6 in the FGA1 group, 92.5, 71.6, 50.9% and 1.5 in the FGA2 group, and 96.2, 89.6, 71.0% and 1.8 in the GnRH group, respectively. No significant difference in estrous response between the groups was recorded, but the fertility rate in the FGA1 and GnRH groups was significantly (P < 0.05) higher than in the FGA2 group. The occurrence of multiple births and litter sizes were significantly (P < 0.05) higher in the GnRH group, compared to both the FGA1 and FGA2 groups, with the number of single lambs being significantly (P < 0.05) higher in the FGA1 (48.4%) and FGA2 (49.0%) groups than in the GnRH (29.0%) group. However, the differences recorded between any of the groups in terms of the number of twin and triplet lambs were insignificant. In conclusion, it can be said that estrous synchronization using the 12-d-FGA-eCG-PGF_2α regimen could be replaced with the 7-d-FGA-eCG-PGF_2α regime in sheep at the onset of the breeding season. However, the combination of GnRH with the latter regimen (7-d-GnRH-FGA-eCG-PGF_2α) increased the multiple birth rate and litter size in the ewes.     

Oestrous behaviour in relation to fertility and fecundity of gilts

The reproductive performance of 2484 gilts was recorded over a 12-month period at a large intensive piggery in southern Australia. Between 29 and 35 weeks of age, gilts were examined daily for response to the back-pressure test (BPT). Those subjectively assessed as showing a moderate or high response were taken to a boar for mating. Gilts that had showed a moderate response to the BPT on their first day of mating had lower average litter size than gilts showing a high BPT response (9.05 and 9.35 piglets, respectively; P < 0.05). A quantitative assessment of sexual receptivity was made while the gilt was with the boar. Gilts that were mated while showing low sexual receptivity on the first day of mating had poorer farrowing rate (78.1 vs. 83.1%, respectively; P < 0.05), as well as lower litter size (9.03 vs. 9.35 piglets, respectively; P < 0.05) than gilts that were mated when showing high sexual receptivity. A moderate BPT response was followed by either low sexual receptivity or failure to mate on 81.4% of occasions, compared with 12.8% for a high BPT response. Since 75% of gilts that showed a moderate BPT response on the first day of mating showed a high response on the following day, it was concluded that mating should only be attempted when gilts exhibit a high response to the BPT. The mean farrowing rate and litter size for gilts at their first farrowing was 82.4% and 9.31 piglets (8.62 alive and 0.69 dead), respectively.     

Effects of chronic treatment with a GnRH agonist on oestrous behaviour and on the secretion of LH and progesterone in the ewe

A study was carried out to investigate a novel approach to oestrus synchronization in the ewe by treatment with a gonadotrophin releasing hormone (GnRH) agonist. Groups of ewes were initially treated on Day 2, 10 or 14 of the oestrous cycle with 10 mug GnRH analogue (D-Ser(Bu(t)) 6 des Gly GnRH ethylamide) per ewe per day for 14 days. Behavioural oestrus was inhibited during GnRH agonist treatment and recurred from 8 to 38 days after the treatment in an unsynchronized manner. Luteal activity during treatment was not impaired but reduced progesterone concentrations occurred in cycles after the treatment. The rhythm of ovarian function, generally characterized by prolonged follicular development, was impaired. During the treatment and subsequent recovery period, integrity of pituitary function was examined by measuring luteinizing hormone (LH) after GnRH agonist was injected, and after stimulation test doses of 150 ng natural GnRH were administered. During treatment there was, with time, a decline in pituitary response to the agonist which suggested that pituitary release of LH was exhausted. After the 14-day treatment the stimulation test with GnRH revealed a gradual return to normal responsiveness although this was not complete three weeks after the treatment when compared to control ewes. This lowered pituitary activity could cause the impaired ovarian function.     

Oestrous behaviour of Dutch Friesian heifers under subtropical conditions in Tunesia

The oestrous behaviour of Dutch Friesian heifers in the subtropical climate of Tunisia is studied. The variables pro- and met-oestrus, oestrus duration, ovulation time and oestrus cycle length are analysed, as well as the influence of season, age and group on these variables. Oestrous behaviour was clearly influenced by the subtropical conditions, adaptation to the high temperatures and low relative humidity is observed.     

Oestrous and ovarian responses to exogenous progesterone and oestrogen in prepubertal ewe lambs in relation to the fecundity of their dams

Oestrus was consistently induced by 20, 40 or 80 microgram oestradiol benzoate in progesterone-primed lambs aged 23 weeks and 17 weeks respectively in two experiments. The duration of oestrus increased linearly with increasing log dose of oestrogen, and was negatively correlated with the time of its onset. In the absence of progesterone there was a reduced incidence, later onset and shorter duration of oestrus. Progesterone alone did not induce oestrus. In lambs treated during January (Exp. 2), a later date of injection of oestrogen was associated with earlier onset and longer duration of oestrus. The induced oestrus was anovulatory. Oestrogen reduced the proportion of lambs with follicles greater than or equal to 3 mm in diameter whilst progesterone had no effect. Lambs which were the progeny of low- and high-fecundity dams did not differ in their oestrous or ovarian responses. Correlations between the dam's lamb production index and the time to onset and duration of the induced oestrus were also not significant.     

Ovarian response in ewes following horse anterior pituitary extract and progestagen treatment

Sixty adult ewes were treated intravaginally for 12 days with one of three progestagen treatments: (1) 500 mg progesterone pessary, (2) 30 mg flurogestone acetate pessary, (3) 12% (w/w) progesterone in a Controlled Internal Drug Release (CIDR) device. On days 10, 11 and 12 of progestagen treatment ewes received either 60, 45 and 30 mg; 45, 45 and 45 mg or 30, 45 and 60 mg of horse anterior pituitary extract (HAP), respectively. Progestagen treatment was terminated on day 12 at the time of the last HAP treatment. Ewes were bred by artificial insemination at 8- and 16-h intervals during oestrus, which was checked by using vasectomized rams. Ovarian response and fertility were determined at laparotomy 8 days after progestagen withdrawal. Progestagen treatment significantly increased (P<0.05) ovulation rate, with a mean of 9.1, 12.0 and 6.6 ovulations from treatments (1), (2) and (3), respectively. The method of HAP administration had no significant effect on ovulation rate, with a mean of 9.8, 10.0 and 7.8 after either decreasing, constant or increasing levels during treatment. There was no difference in the fertilization rate following flurogestone acetate (45.7%) or CIDR (47.0%), but a lower rate resulted after the progesterone pessary (30.0%) (P<0.025). More eggs were recovered following local than following general anaesthesia (P<0.05). Results indicate that cervical insemination does not give a satisfactory yield of fertilized eggs following hormonal inductions of superovulation.     

Timing of multiple ovulations in the ewe after treatment with FSH or PMSG with and without GnRH

Ovulation rate, median time to first ovulation, median time of all ovulations and median time from first to last ovulation were studied by repeated laparoscopy in Merino ewes. Treatments with FSH or PMSG significantly affected ovulation rate (8.4 +/- 0.81 and 7.3 +/- 1.21 respectively, P less than 0.05) and in median time of all ovulations (60 and 54 h respectively after progestagen sponge removal, P less than 0.05). Differences in the median time to first ovulation (60 and 48 h) and median time from first to last ovulation (6 and 6 h) for the respective treatments were not significant. The synchrony of ovulation after both treatments was adversely affected by (1) the occurrence of premature ovulations before the onset of superovulation, (2) variability in the time of commencement of superovulation, and (3) variability in the time from first to last ovulation. Administration of GnRH synchronized the timing of ovulation with both gonadotrophin treatments. This synchrony was due to a reduction in the period during which superovulation began and in the interval from first to last ovulation. The median time of all ovulations was significantly less with FSH + GnRH than with PMSG + GnRH (45 and 48 h after progestagen sponge removal, respectively, P less than 0.05). Administration of GnRH at 16, 20 or 24 h after progestagen sponge removal significantly affected all traits examined except ovulation rate. Administration at 20 and 24 h produced an equally good synchrony of ovulation which was better than that obtained at 16 h. We suggest that the use of GnRH in embryo collection programmes appears justified and is likely to improve embryo yields due to improved rates of fertilization.     

Inhibition and subsequent rebound of FSH secretion following treatment with bovine follicular fluid in the ewe

Plasma concentrations of gonadotropins were examined after treatment of ewes with bovine follicular fluid (FF) in four experiments. Mean concentrations of FSH were significantly decreased by FF treatment. The FSH depression appeared to continue throughout the length of treatment when the duration of treatment was 2-4 days. However, in an experiment in which the treatment period was 8 days, mean concentrations of FSH initially declined and then returned to control levels during the last 4 days of treatment. In all experiments, a rebound in FSH concentrations was found 24-36 h after cessation of FF treatment. The magnitude of this rebound appeared to be proportional to the degree of FSH suppression during FF treatment.     

Some Behavioural Changes Associated with the Guinea-pig Oestrous Cycle

This paper describes some behaviour patterns of the guinea-pig, Cavia porcellus, which vary systematically with the oestrous cycle. Oestrus is characterised by an increase in locomotion, and scent-marking, as well as by greater interest in conspecifics. All of these are behaviours known to increase at oestrus in other rodent species. The significance of these changes for the social organisation of this species is discussed.     

Effect of type of intravaginal progestagen treatment of estrous response and reproductive performance of ewes

A comparison was made of the relative effectiveness of sponge pessaries impregnated with 40mg flourogestone acetate (FGA) or 60mg medroxyprogesterone acetate (MAP) to induce a synchronized estrus in ewes. Ewes were treated with sponge pessaries for 14 days and 500 IU pregnant mares' serum gonadotropin was injected i.m. at the time of sponge removal. The degree and pattern of mating response of ewes were similar, irrespective of the treatment used, approximately 92% of the ewes being marked by the ram by 72h after sponge removal. No significant differences in fertility or litter size were observed between the treatment groups. Ewes treated with FGA sponges had a fertility of 53% and litter size of 2.3 after mating at the synchronized estrus. The corresponding values for ewes treated with MAP sponges were 57% and 2.1. Use of MAP sponges was associated with a 17.8% sponge loss during treatment compared with 1% sponge loss in ewes treated with FGA sponges. Such losses could compromise the use of MAP sponges by reducing their overall efficacy.