Synchronization of oestrus and ovulation by short time combined FGA, PGF(2α), GnRH, eCG treatments for natural service or AI fixed-time

Two experiments were conducted in ewes in order to develop an oestrus-ovulation short time synchronization protocol based on combined FGA, PGF(2α), GnRH, eCG treatments, for use in dairy sheep before natural service (Experiment 1) or for fixed-time artificial insemination (Experiment 2), during the breeding season. In Experiment 1 seventy-five non-lactating dairy ewes were subdivided into 5 treatment groups (N=15): (1) Group Fe - control, which received FGA vaginal sponges (14 days)+eCG (Day 14); (2) Group FPe, FGA (5 days)+PGF(2α) (Day 5)+eCG (Day 5); (3) Group PFe, PGF(2α) (Day 0)+FGA (5 days)+eCG (Day 5); (4) Group PFG, PGF(2α) (Day 0)+FGA (5 days)+GnRH (30h after sponge removal, s.r.); (5) Group GPe, GnRH (Day 0)+PGF(2α) (Day 5)+eCG (Day 5). Ewes were checked for oestrus and hand-mated. Time of ovulation was recorded by laparoscopy for 10 animals from each treatment. The percentages of female in oestrus and the interval to oestrus (h after treatment), fertility and prolificacy rate were recorded. There were no treatment differences in the percentage of females in oestrus. The interval to oestrus was earlier in Fe Group and delayed in FPe Group (P<0.01). Ovulation time was earlier in GPe Group compared to FPe Group (P<0.05). Fertility rates were significantly different (P<0.05) between the PFe and the FPeG Groups compared with the PFG Group. No significant differences were observed in prolificacy among the treatments. In Experiment 2, sixty dry ewes were subdivided (N=20) into the following three experimental treatment groups: (1) Group FP, FGA (5 days)+PGF(2α) (Day 5); (2) Group FPG, FGA (5 days)+PGF(2α) (Day 5)+GnRH (30hs.r.); (3) Group FPeG, FGA (5 days)+PGF(2α) (Day 5)+eCG (Day 5)+GnRH (30hs.r.). These were further subdivided into two groups (N=10) corresponding to 52 and 60hs.r. fixed-time insemination. Laparoscopic intrauterine insemination was performed with frozen semen (80×10(6)spermatozoa/dose) and ovulation time was recorded in a subgroup (N=10). GnRH resulted in an earlier ovulation time (P<0.05) in FPG and FPeG Groups (53.0h vs 61.6h). Fertility rate was higher in FPeG treated ewes inseminated at 60hs.r. (60%, 6/10). In FP and FPG Groups fertility rates were higher following insemination at 52hs.r. (50.0 and 40.0%).     

Ovulation and ovulation rate in ewes under grazing conditions: factors affecting the response to short-term supplementation

The relationships between ovulation rate and nutrition remain confused, probably because of uncontrolled variation in experimental conditions. To help resolve the problem, we analyzed data from 20 experiments conducted between 2002 and 2016, in Uruguay with grazing ewes. All experiments were carried out by a single laboratory under comparable conditions of experimental design and measured variables. The studies used a total of 3 720 ewes, of purebred Corriedale, Polwarth, or East Friesian x Polwarth genotypes. In all experiments, a control group grazed native pastures and extra nutrition was provided to the treatment groups using either improved pastures or supplements. Ovulation rate was measured by counting corpora lutea using laparoscopy or rectal ultrasound or by counting foetuses at ultrasound on day 45 of gestation. For statistical analysis, data were grouped according to nutritional treatment (control or supplemented) and, within these groups, type of supplement to provide energy or protein (protected or not from rumen degradation). Across all experiments, 92–99% of the ewes ovulated and the effects of diet, length of supplementation, and initial live weight and genotype are reported. Within diets, ovulation was most affected by overall energy intake during supplementation (P < 0.01). Ewes that grazed native pastures supplemented with protein supplements had higher ovulation rates (P < 0.05) than control ewes grazing only native pastures. The addition of tannins to the protein supplement, to protect it from degradation in the rumen, did not further increase the ovulation rate. In unsupplemented ewes that had access to legume pastures, ovulation rates did not increase when the legume pasture was rich in tannins although only ewes that grazed tanniniferous legumes had marginally higher ovulation rates than the control ewes (P < 0.05). When ewes grazing native pastures were supplemented with energy, their ovulation rate did not increase above those of nonsupplemented ewes. Live weight at the start of supplementation also affected ovulation rate. We conclude that ovulation was most affected by overall energy intake, whereas the factors that affected ovulation rate during short-tern nutritional supplementation were intake of protein from highly digested supplements or dietary protein protected from ruminal degradation.     

Effects of progesterone-impregnated sponge treatment on peripheral plasma hormone levels and fertility in the cyclic ewe

Cyclic ewes were treated with 500-mg progesterone-impregnated sponges for the synchronization of oestrus. In the first experiment, the sponges were removed from 79 ewes at intervals over a 17-day treatment and the residual amount of progesterone was measured in order to assess the rate of absorption of the hormone from the sponges by the animals. The residual progesterone was found to decrease linearly with the duration of sponge insertion but there was also a significant quadratic component indicative of a slowing down in the rate of progesterone absorption towards the end of the treatment period. In the second experiment, 13 cyclic ewes were treated with 500-mg progesterone sponges for 17 days and the eight ewes in oestrus following spongewithdrawal were mated. The peripheral plasma progesterone was assayed at intervals during sponge insertion and at weekly intervals after sponge withdrawal. The residual progesterone levels on the sponges and the plasma progesterone levels of the treated ewes were examined in relation to their oestrous response and fertility. There was a significantly higher residual level of hormone remaining on sponges from ewes that mated than on sponges from those that did not (P < 0.01). The 13 ewes exhibited luteal phase levels of plasma progesterone when assayed during the period of sponge insertion regardless of their response to treatment. The mated, fertile ewes had significantly higher plasma hormone levels than the non-mated and the mated infertile ewes, after sponge withdrawal.     

The effects of nutrition on the reproductive performance of Finn x Dorset ewes. II. Post-partum ovarian activity, conception and the plasma concentration of progesterone and LH.

After lambing forty-five ewes were allocated to three groups, two of sixteen and one of thirteen ewes. The lambs of the two groups of sixteen ewes were weaned on Day 1 after lambing and the ewes were fed a diet of 100% (Group H) or 50% (Group R) of maintenance energy requirements. The thirteen ewes in the third group (Group L) suckled twin lambs and were fed freely. During the first 3 weeks after lambing, oestrus was observed for 11/16 (Group H) and 8/16 (Group R) ewes; of the ewes which had shown oestrus in the two groups, ovulation occurred in 5/8 and 5/7 respectively. Only 1/13 Group-L ewes showed oestrus and ovulated during the same period. The mean plasma concentrations of progesterone and LH were unaffected by the treatments and were around 0-4 and 1-5 ng/ml, respectively. Restricted feeding had no effect on oestrus, ovulation or the hormone levels during the oestrus cycle following synchronization. The onset of oestrus and the start of the preovulatory discharge of LH were 3 and 6 hr later, respectively, in the lactating ewes (Group L) than in those in Groups H and R. Ewes in Group L also had a higher ovulation rate, 2-8 +/- 0-2 versus 2-1 +/- 0-2 (P less than 0-05). Restricted feeding reduced the number of ewes lambing; only 1/11 ewes in Group R, considered to have conceived because of the presence of high progesterone levels 17 days after mating, subsequently lambed compared with 6/12 in Group H and 5/9 in Group L.     

Simplified superovulatory treatments in Corriedale ewes

Two experiments were designed to evaluate the possibility of simplifying superovulatory treatments in Corriedale ewes with use of ovine FSH (oFSH). Ewes received intravaginal progestogen sponges for 14 days. In Experiment 1, several simplified schedules were tested. Ewes were treated with 176 NIH-FSH-S1 units' oFSH given as a single injection in saline, along with 500 IU eCG 48 h before sponge removal (Group A1), in four equal doses (B1), or given as a single injection in a polyvinylpyrrolidone vehicle (C1) 24 h before sponge removal. In Experiment 2, the simplified protocol that exhibited the most desirable results in Experiment 1 (A2) was compared with the same protocol, but using less oFSH (132 units) (B2) and with the most conventional protocol (176 units of oFSH in eight decreasing doses; C2). Estrus was detected and ewes were naturally mated. The ovarian response and embryo production were assessed on Day 6 after estrus. LH was measured at 6h intervals from pessary withdrawal. The onset of estrus and the pre-ovulatory LH surge were advanced (P<0.05) in ewes treated with FSH and eCG. In Experiment 1, protocol A1 produced a greater percentage of superovulated ewes compared to C1 (100.0 compared with 58.3%; P<0.05), increased ovulation rate (13.8 corpora lutea compared with 6.2 and 4.7 for B1 and C1, respectively; P<0.05), and tended to increase the number of transferable embryos compared to B1 (P=0.08). In Experiment 2, percentages of superovulated ewes and ovulation rates were similar among groups; however, Group A2 tended to have more large follicles (P=0.07) than C2. The number of transferable embryos was similar among the three treatments. In conclusion, the reduced-dose oFSH given once along with eCG is the most appropriate superovulatory treatment because it combines simplicity and a lesser dose of gonadotropin, which also implies a reduction in cost, without reducing embryo production.     

Effect of anti-oestradiol-17B antibodies on the reproductive response of ewes superovulated with PMSG

A field experiment was conducted to examine the effect of anti-oestradiol-17B antibody titre on the oestrous and ovulatory responses of ewes to low (600 i.u.) or high (1200 i.u.) doses of pregnant mare's serum gonadotrophin (PMSG). Merino ewes were treated with intravaginal sponges and were subsequently used as vehicle-treated controls or were immunized to produce reciprocal anti-oestradiol-17B antibody titres less than 1000 or greater than 1000. Ewes were then treated with PMSG and the incidence of oestrus and ovulation, ovulation rate, and yield of embryos recorded. Treatment of immune ewes with 1200 i.u. PMSG resulted in both a higher proportion of ewes ovulating and a higher ovulation rate than in immune ewes treated with 600 i.u. (86% v. 67% and 13.4 v. 6.0 respectively). As anti-oestradiol-17B titres increased there was a reduction in the proportion of ewes exhibiting oestrus. The proportion of ewes ovulating decreased as antibody increased in ewes treated with 600 i.u. PMSG but not in those treated with 1200 i.u., suggesting an increased positive feedback of oestradiol with high PMSG doses. Fertilization rates were highest at the lower PMSG dose (68% v. 42%) and increased with increasing titre. Overall, there was no increase in ovulation rate or in yield of embryos over control values from either low (less than 1000) or high (greater than 1000) antibody titres.     

Induction/synchronization of oestrus and ovulation in dairy goats with different short term treatments and fixed time intrauterine or exocervical insemination system

Two experiments were carried out on Ionica dairy goats in order to test the efficiency of: (1) short term-5-day combined progestogen-PGF2α-GnRH treatments on induction/synchronization of oestrus and fertility after natural mating in lactating goats and during the transition period (Experiment 1); (2) short term-9-day FGA-PGF2α-eCG treatments on synchronizing oestrus and ovulation (Experiment 2.1) and artificial insemination (AI) fixed time system in synchronized does (Experiment 2.2), during the breeding season. In Experiment 1, four treatment groups (N=24) were considered: (1) FPe-11d - control, FGA intravaginal sponges (11 days)+PGF2α (9th d)+eCG (11th d); (2) FPe-5d, FGA (5 days)+PGF2α (5th d)+eCG (5th d); (3) PFe-5d, PGF2α (D0)+FGA (5 days)+eCG (5th d); (4) GPe-5d, GnRH (D0)+PGF2α (5th d)+eCG (5th d). Goats were checked for oestrus and naturally mated. The occurrence of oestrus was 75.0, 78.3, 86.4, and 58.3% for groups 1-4, respectively, with significant differences (P<0.05) between groups 3 and 4. Interval to oestrus was earlier (P<0.05) in GPE-5d than in FPe-11d control group. There were no differences between the groups (P>0.05) in fertility or in prolificacy. In Experiment 2.1, 22 goats were subdivided into two treatment groups (N=11): (T1) FPe-11d (control), FGA (11 days)+PGF2α (9th d)+eCG (11th d); (T2) FPe-9d, FGA (9 days)+PGF2α (7th d)+eCG (9th d). Oestrus and ovulation times were monitored every 4h; ovulation rate was also determined. The induction of oestrus ranged from 91 to 100% and all goats ovulated. Intervals to oestrus, from the onset of oestrus to ovulation, from sponge removal to ovulation, and ovulation rates were 28.2±4.9 and 26.0±4.0h, 25.3±9.2 and 28.9±7.4h, 53.5±7.6 and 54.9±7.1h, 3.7±1.6 and 2.4±1.4 corpora lutea (P<0.05) for T1 and T2, respectively. In T2 a great abnormal ovulatory response was observed. In Experiment 2.2, 48 goats were synchronized with FPe-9d treatment and subjected to AI, performed 50h after s.r. with frozen semen, and subdivided into 2 AI system groups (N=24): T3, exocervical AI (100×10(6)Spz/doe); T4, intrauterine AI (20×10(6)Spz/doe). Fertility rate was higher (P<0.05) in T4. It seems that short term-5-day combined progestogen-PGF2α-GnRH-eCG treatments need to be investigated for AI fixed time.     

Effects of prostaglandin administration on ovarian follicular dynamics, conception, prolificacy, and fecundity in sheep

Two experiments were conducted to determine the effects of prostaglandin administration on ovarian follicular dynamics, conception, prolificacy, and fecundity in sheep. During the breeding season, multiparous Corriedale ewes were randomly allocated to two groups: 1) PG group (n = 15 and n = 135 in Experiments I and II, respectively): synchronized with two injections of DL-Cloprostenol (125 μg) given 7 d apart, and inseminated at a fixed time (Day 0), 48 h after the second injection; and 2) Control group (n = 15 and n = 73 in Experiments I and II): ewes in spontaneous estrus inseminated at detected estrus. Ewes received 100 × 10⁶ sperm by intrauterine AI. Ultrasonography was used to evaluate growth of the ovulatory follicle, ovulation rate (OR), conception rate, and prolificacy on Days 30 and 60. Ewes from the group PG had a larger (4.8 ± 0.5 mm, mean ± SEM; P < 0.05) ovulatory follicle that grew faster (1.2 ± 0.3 mm/d, P = 0.08), and a lower OR (1.37 ± 0.1, P < 0.05), compared to ewes from the Control group (3.9 ± 0.2 mm, 0.7 ± 0.2 mm/d, and 1.61 ± 0.1 respectively). Plasma progesterone concentrations from Days −6 to 1 were lower in the PG group (P < 0.05), but plasma estradiol concentrations were similar between groups (P > 0.05). Progesterone concentrations were similar between groups during the early luteal phase and on Days 12 and 17 (P > 0.05). The embryo recovery rate (Day 7) tended to be lower in the PG group (39 vs 64%, P = 0.08), but embryo quality did not differ between groups. Conception, prolificacy and fecundity, were lower in the PG than in the Control group (P < 0.05). Cumulative reproductive losses were similar between groups, but more twins were lost in the PG group (P < 0.05). We concluded that in ewes synchronized with PGF_2α given twice, 7 d apart, lower reproductive performance was associated with an environment dominated by lower progesterone concentrations that stimulated the preovulatory follicle to grow faster and become larger; this was associated with lower rates of ovulation, conception, prolificacy, and fecundity.     

Ovulation of aged follicles does not affect embryo quality or fertility after a 14-day progestagen estrus synchronization protocol in ewes

The aim was to examine the effect of ovulation of aged follicles on embryo quality and fertility in ewes. In Experiment 1, ewes (n = 39) received a prostaglandin analogue on Day 6 of the cycle and then received either a progestagen sponge from Day 6 to 20 after estrus (Single sponge) or a progestagen sponge on Day 6 that was replaced on Day 11 and 16 and removed on Day 20 (Multiple sponges). In a subgroup of ewes, the growth of ovarian follicles was characterised using ultrasonography. Fertile rams were introduced 48 hours after sponge withdrawal; we slaughtered the ewes on Day 5 of pregnancy and recovered the embryos. The mean age of the ovulatory follicles was greater in ewes that received a single sponge compared with multiple sponges (8.7+/-0.8 days, range 4 to 14, versus 4.5+/-0.7 days, range 3 to 6; P<0.05). However, the groups did not differ (P>0.05) in ovulation rate (2.4+/-0.3 corporal lutea per ewe) or the proportion of good quality embryos recovered (71 to 82%; developed to the early morula stage or further). In Experiment 2, ewes (570 in total) received treatments similar to those in Experiment 1 but were kept until lambing. Ewes that received a single sponge came into heat earlier (P<0.05) than those that received multiple sponges, but > or = 97% of ewes in all groups (P>0.05) were bred by 48 to 72 hours after ram introduction. There was no difference (P>0.05) between groups for the proportion of ewes that lambed to first service (80 to 86%) or the number of lambs per ewe (1.94+/-0.08 lambs). We conclude that when luteolysis occurs at the beginning of progestagen synchronisation, ewes will ovulate aged follicles, but that compared to shorter duration follicles, these follicles produce oocytes that are equally competent to be fertilised and develop into good quality embryos and full-term lambs.     

Ovulation rate in ewes after single oral glucogenic dosage during a ram-induced follicular phase

A 2-factor factorial array with three replicates (N = 280) was used to simultaneously assess the effects on ovulation rate of two alternative doses of medroxy-progesterone acetate (MPA) (10 or 60 mg), applied during a 6-day priming period, and the effect of a single dosage of a glucogenic formulation, administered immediately before ram exposure to groups of adult seasonally anovular Corriedale ewes. The glucogenic formulation contained 1,2,3-propanetriol (glycerol; 70% $\text{v}\text{v}$), 1,2-propanediol (propylene glycol; 20% $\text{v}\text{v}$) and distilled water (10% $\text{v}\text{v}$). At sponge withdrawal, a single oral dose of 100 ml of this formulation or the same volume of distilled water was administered to treated and control groups, respectively, and ewes were immediately exposed to rams and hormonally-induced oestrous ewes. Data from an ancillary experiment (n = 10) showed significantly (P < 0.005) above normal plasma glucose levels in treated animals at 3 and 6 h after dosage. A significant interaction (P = 0.0006) between MPA priming doses and glucogenic supplementation was detected. Supplemented ewes, among those exposed to the lower dose of MPA, exhibited a higher (P = 0.0098) mean ovulation rate (1.56 ± 0.076) than ewes that did not receive glucogenic treatment (1.31 ± 0.060). In contrast, ovulation rate was significantly decreased (P = 0.021) from 1.30 ± 0.058 to 1.13 ± 0.042 after glucogenic treatment in ewes that were primed with sponges containing 60 mg of MPA. Ewes exposed to 60 mg of MPA were marked by the rams at a significantly later (P < 0.00001) mean time (54.8 ± 1.44 h) than ewes receiving 10 mg sponges (43.6 ± 1.08 h). These results reveal the potential for modifying ovulation rate through short-term glucogenic manipulations, at least during the compressed follicular phase typical of ram-induced ovulations.     

Effect of monensin and progesterone priming on ram-induced reproductive performance of boutsiko mountain breed ewes

The effects of monensin and progesterone priming on reproductive performance (estrous response, lambing rate and prolificacy) of grazing Boutsiko mountain breed adult and 18-mo.-old ewes at the end of seasonal anestrus were investigated. In Experiment 1 the feed supplement with or without monensin was offered for 21 d after introduction of vasectomized rams (Day 0). Progesterone was administered to the ewes in the respective groups as a single injection at Day -3. Ewes of both age groups were assigned randomly to 1 of 4 treatments: C, C+P, C+M and C+M+P. In Experiment 2 the supplement C or M was offered from Day -26 to Day 21. The treatments consisted of C, C+P and C+M+P. Blood samples were taken 50 h after ram introduction for determination of plasma concentrations of P and insulin-like growth factor-I (IGF-I). There was a greater increase in estrous response at Days 17 to 19 and at Days 0 to 19 when supplementation was offered before rather than after ram introduction in both age groups. In the adult group ewes synchronization of estrus at Days 17 to 19 was significantly increased by administration of monensin (P<0.05) and progesterone (P<0.01) compared with the control group in the first but not the second experiment. The incidence of estrus at Days 17 to 19 or at Days 0 to 19 was highest in the adult groups treated with monensin and progesterone in both experiments. In 18-mo.-old ewes progesterone was effective in synchronizing estrus only in Experiment 2. Mean plasma IGF-I concentrations were increased by monensin treatment (P<0.05) in adult ewes that were at the periovulatory stage at blood sampling time. Correlation coefficients between IGF-I and progesterone concentrations in monensin plus progesterone group adults were -0.715 (P<0.02) and -0.516 (P<0.01), respectively across all treatments. The results suggest that monensin and progesterone priming improved reproductive performance, and the monensin-induced increase in plasma IGF-I levels at the periovulatory stage may be causally related to the ability of ovulatory follicles to develop into functional corpora lutea (CL).     

Endocrine and Ovarian Changes in Response to the Ram Effect in Medroxyprogesterone Acetate-primed Corriedale Ewes During the Breeding and Nonbreeding Season

Two experiments were performed to determine the endocrine and ovarian changes in medroxyprogesterone acetate (MAP)-primed ewes after ram introduction. Experiment 1 was performed during the mid-breeding season with 71 ewes primed with an intravaginal MAP sponge for 12 days. While the control (C) ewes (n = 35) were in permanent contact with rams, the ram effect (RE) ewes (n = 36) were isolated for 34 days prior to contact with rams. At sponge withdrawal, all ewes were joined with eight sexually experienced marking Corriedale rams and estrus was recorded over the next 4 days. The ovaries were observed by laparoscopy 4–6 days after estrus. Four weeks later, pregnancy was determined by transrectal ultrasonography. In eight ewes from each group, ovaries were ultrasonographically scanned; FSH, LH, and estradiol-17β were measured every 12 hours until ovulation or 96 hours after estrus. The response to the rams was not affected by the fact that ewes had been kept or not in close contact with males before teasing. No differences were found in FSH, LH, estradiol-17β concentrations, growth of the ovulatory follicle, onset of estrus, ovulation rate, or pregnancy rate. Experiment 2 was performed with 14 ewes during the nonbreeding season. Ewes were isolated from rams for 1 month, and received a 6-day MAP priming. Ovaries were ultrasonographically scanned every 12 hours, and FSH, LH, estradiol-17β, and progesterone were measured. Ewes that ovulated and came into estrus had higher FSH and estradiol-17β levels before introduction of the rams than did ewes that had a silent ovulation. The endocrine pattern of the induced follicular phase of ewes that came into estrus was more similar to a normal follicular phase, than in ewes that had a silent ovulation. The follicle that finally ovulated tended to emerge earlier and in a more synchronized fashion in those ewes that did come into estrus. All ewes that ovulated had an LH surge and reached higher maximum FSH levels than ewes that did not ovulate, none of which had an LH surge. We conclude that (a) the effect of ram introduction in cyclic ewes treated with MAP may vary depending on the time of the breeding season at which teasing is performed; (b) patterns of FSH, and estradiol-17β concentrations, as indicators of activity of the reproductive axis, may be used to classify depth of anestrus; and (c) the endocrine pattern of the induced follicular phase, which is related to the depth of anestrus, may be reflected in the behavioral responses to MAP priming and the ram effect.     

Fertilization and early embryonic development in androstenedione-immunized Merino ewes

Ewes were immunized against androstenedione (Fecundin) and assigned to be mated 14 days (179 ewes Group C) or 25 days (174 ewes Group B) after a booster immunization with Fecundin. The anti-androstenedione titres at these times were 6790 and 3240 respectively (P less than 0.01). The remaining 169 ewes were untreated controls (Group A). Ewes were mated to entire rams (12 rams to 180 ewes) at their second oestrus after synchronization of oestrus. Immunization against androstenedione caused a shortening of the time from sponge removal to mating (Day 0) and a decrease in the percentage of ewes mated by the rams. Also, ovulation rate was increased after immunization (P less than 0.01), being 1.42, 2.16 and 1.93 for Groups A, C and B respectively. Egg recovery rates on Day 2 were lower in immunized ewes and there was some indication that fertilization rates were lowered. On Day 13 after mating a higher proportion of blastocysts was recovered from ewes in Group A than from those in Groups B and C. Immunization resulted in lower fertilization rates and smaller blastocysts with lower mitotic indexes (P less than 0.01). At Days 24-32 of pregnancy fetal weight was lower in the immunized ewes. At all sampling stages, the proportion of ewes pregnant (fertility) was lowered in immunized ewes. The results of the present study show that significant reproductive wastage occurs in androstenedione-immunized Merino ewes, with lower rates of embryo recovery and delayed embryonic development being found in comparison to controls.(ABSTRACT TRUNCATED AT 250 WORDS)     

Oestrus, time of ovulation, ovulation rate and conception rate in progestagen-treated ewes given Gn-RH, Gn-TH analogues and gonadotrophins.

The influence of Gn-RH, hCG and a PMSG-hCG mixture (PG600) on the time of ovulation, ovulation rate and on the occurrence of oestrus in ewes treated with progestagen-impregnated sponges for 12 days examined. The effects of Gn-RH analogues on plasma LH, oestrus, ovulation and conception rate were also investigated. Six separate experiments were carried out. When 50 micrograms Gn-RH were given 24 h after sponge removal ovulation occurred in 44--46% of ewes within 24 h and in all ewes by 34 h. Gn-RH was a more potent ovulation synchronizer than hCG. Both hCG and PG600 reduced the incidence of overt oestrus. Gn-RH also had this effect in ewes treated during February and May but not in August and September. Gn-RH analogues given 2 days before sponge removal significantly increased ovulation rate. The display of oestrus was not affected in ewes treated 2 days before sponge removal but was suppressed in 43-69% of ewes treated with an analogue at the time of sponge removal. Ovulation occurred in 50-62% of ewes within 30-35 h of injection of Gn-RH analogues, regardless of the time of their administration. The release of LH in response to one analogue was not influenced by the presence of the progestagen-impregnated sponge in the vagina. When given a Gn-RH analogue 2 days before sponge removal or at the time of sponge removal 63 and 62% of mated ewes became pregnant compared with 70% of control ewes.     

Effects of active immunization against a synthetic peptide sequence of the inhibin alpha-subunit on plasma gonadotrophin concentrations, ovulation rate and lambing rate in ewes.

Thirty adult Mule (Blue-faced Leicester x Swaledale) ewes were actively immunized against a synthetically produced peptide corresponding to the N-terminus of the alpha-subunit of bovine inhibin conjugated to tuberculin purified protein derivative (PPD). Primary immunization in the late anoestrous period was followed by two booster injections at 5 week intervals. Control groups were either not immunized (n = 15) or received PPD only (n = 15). Ten days after the second booster, oestrus was synchronized using progestagen sponges and ovulation rate was assessed by laparoscopy on days 9-10 of the cycle. Blood samples were taken at the time of each immunization and immediately before laparoscopy. Ewes were mated with fertile rams in mid-November and the resulting conception, pregnancy and lambing rates monitored. All inhibin-immunized ewes generated antibodies that bound 125I-labelled native bovine inhibin (M(r) 32,000), and their plasma follicle-stimulating hormone (FSH) concentrations after the second booster were significantly higher than the preimmunization values (30%; P less than 0.001) and the corresponding value in the controls (25%; P less than 0.025). Inhibin immunization was associated with a 90% increase in ovulation rate (P less than 0.005) and had no adverse effect on conception rate (100%), pregnancy rate (100%) or length of gestation (146 days). However, only a 37% increase (P less than 0.05) in lambing rate was recorded for inhibin-immunized ewes, indicating a higher incidence of wastage of ova, or embryos, or both, in these ewes.(ABSTRACT TRUNCATED AT 250 WORDS)     

A definition of the breeding season of Pool Dorset ewes

The seasonality of oestrus and ovulation of 62 Poll Dorset ewes was examined over a period of 16 months commencing October, 1981. Laparoscopic observations showed that the majority of these ewes were anovular during the South Australian spring and early summer (September to December). The number of ewes with corpora lutea (93.6%) and the mean ovulation rate (1.62) reached a peak in June. Oestrus was stimulated in anovular ewes in late spring by the introduction of vasectomised rams. The mean ovulation rate at the teased ovulation was 1.68, although teased ewes did not exhibit oestrus at this ovulation.     

Reproductive responses following royal jelly treatment administered orally or intramuscularly into progesterone-treated Awassi ewes

An experiment was conducted to determine whether natural royal jelly (RJ) paste administered orally or intramuscularly (i.m.) in conjunction with exogenous progesterone is associated with improved reproductive responses in ewes. Thirty 3-6-year-old Awassi ewes were randomly allocated into three (RJ-capsule, RJC; RJ-injection, RJI and control, CON) groups of 10 ewes each. All ewes were treated with intravaginal progesterone sponges for 12 days. Ewes in the RJC and RJI were administered orally or i.m. with a total of 3g of RJ given in 12 equal doses of 250 mg per ewe per day starting at the time of sponge insertion. At the time of sponge withdrawal (day 0, 0 h), ewes were exposed to three rams and checked for breeding marks at 6-h intervals for 3 days. Blood samples were collected from all ewes for analysis of progesterone concentrations. Pretreatment progesterone levels were <0.5 ng x ml(-1) in 16/30 and >1.3 ng x ml(-1) in the remaining ewes indicating luteal function and cyclicity. Similar reproductive responses and progesterone levels occurred in ewes of the RJC and RJI; therefore, data of the two groups were pooled. Following sponge insertion, progesterone levels increased rapidly and reached maximum values of 5.8+/-0.2 ng x ml(-1) within 2 days among ewes of the three groups, and then declined gradually to day 0 values of 1.6+/-0.1 and 1.9+/-0.1 ng x ml(-1) for the RJ-treated and CON ewes, respectively. The rate of progesterone decline was greater (P<0.001) in RJ-treated than in CON. Mean progesterone levels during the 12-day period were lower (P<0.001) in RJ-treated than in CON (2.8+/-0.2 ng x ml(-1) versus 3.3+/-0.2 ng x ml(-1)). Treatment with RJ resulted in greater (P<0.05) incidence of oestrus and shorter (P<0.05) intervals to onset of oestrus than CON. Based upon progesterone levels, ovulation occurred following day 0 in all ewes. Progesterone increased on day 3 in RJ-treated and on day 4 in CON ewes. Progesterone remained elevated through day 18 in 8/20 RJ-treated and 1/10 CON ewes (P=0.09). All pregnant ewes exhibited oestrus 14 h earlier (P<0.02), ovulated approximately 1 day earlier and had higher (P<0.001) luteal phase progesterone levels than non-pregnant ewes. Non-pregnant had higher (P<0.04) body weights than pregnant ewes. In conclusion, results demonstrate that both RJ treatments in conjunction with exogenous progesterone were equally capable of improving oestrus response and pregnancy rate.     

Control of fertility and fecundity of sheep by means of hormonal manipulation

The results of four experiments are presented in summary form. The data are considered in relationship to the improvement of the fecundity and fertility of the Australian ewe breeding flock. In the first, three commonly used methods of oestrous synchronization were examined and showed differences that are attributed to the different patterns of hormonal changes associated with the methods demonstrated. The second experiment looked at the use of active immunization against testosterone and concluded that this method can improve fecundity but not fertility. The third experiment, a group of five trials, studied the use of progestagen sponges and PMSG in anoestrous ewes as a means of inducing normal fertility. The extensive data produced in this experiment allowed the relationships between ovulation rate and fertility and between fertility and prolificacy (fecundity) to be examined. Fertility appeared greatest when the mean flock ovulation rate was about 2.5. At this ovulation rate prolificacy was also improved and a high proportion of twins were produced. We concluded that high fertility and low prolificacy (i.e. of 1.00) are an unlikely combination. In the final experiment the effect of post-mating hormonal supplementation on fertility was examined and a number of earlier reports were confirmed by showing that fertility can be improved with supplementary progesterone between days 10 and 25 post-mating. The effect appears to be modified by hormonal and nutritional factors.     

Fertility of sheep given antisera to steroids during anoestrus

The incidence of oestrus (6/46) and ovulation (14/46) in ewes given antisera to androstenedione, oestrone, oestradiol and testosterone either separately or as a mixture of these sera at the time of treatment with progestagen sponges alone or progestagen sponges followed by LH-RH was similar to that of control ewes (2/13 and 6/13 respectively). The number of corpora lutea (CL) recorded for those ewes that did ovulate was, however, greater in the antiserum-treated ewes (22 CL/14 ewes) than in the controls (6 CL/6 ewes) at the first ovulation after sponge withdrawal. This superiority persisted to the second ovulation (53 CL/42 treated ewes compared to 13 CL/13 controls). The results for groups treated with antisera did not differ amongst themselves.     

Seasonal variation in oestrus, the secretion of oestrogen and progesterone and LH levels before ovulation in the ewe

Ewes with cervical ovarian autotransplants were studied after PGF-2alpha-induced luteal regression in November and February (mid- and late-breeding season) and June (anoestrum). Progesteron and oestradiol-17beta secretion rates and LH concentrations were determined in serial ovarian venous blood samples and the ewes were frequently tested for oestrus. All 4 ewes in November and 3 of the 4 ewes in February exhibited oestrus and endocrine changes indicative of ovulation. The remaining ewe in February and the three ewes in June failed to show elevated oestradiol-17beta secretion rates after luteal regression, indicating the absence of follicles in the final stages of maturation. The preovulatory rise in the oestradiol-17beta secretion rate, the LH surge and the display of oestrus all occurred earlier, with respect to the PGF-2alpha infusion, in November than in February, suggesting a greater stimulation of folliculogenesis, and therefore a greater availability of maturing follicles, in November than in February.