Ovarian response and pregnancy rate following different doses of eCG treatment in Chall ewes

The purpose of the study was to investigate the effects of different doses of equine chorionic gonadotropin (eCG) treatment on follicular development, ovulation and pregnancy rate during the breeding season in fat-tailed Chall ewes. Seventy-two cycling (62.5 ± 2.5 kg), multiparous Iranian Chall ewes were used in the trial. The ewes were randomly allocated to 6 groups (n = 12/group). Estrus was synchronized with the aid of controlled intravaginal drug release (CIDR) devices, inserted for 14 days. At the time of CIDR removal (day 14), the ewes received i.m. either 0 (control group, G0), 450 (G450), 550 (G550), 650 (G650), 750 (G750) or 850 (G850) IU eCG. Vasectomized rams were used to detect estrus in the ewes from 24 h after CIDR removal. Ovarian follicular activity was monitored with the aid of transrectal ultrasonography on the day of CIDR insertion (day 0) and daily from the day of eCG treatment (day 14), until estrus (day 16). During these days, blood samples were collected for the determination of plasma progesterone and estradiol concentrations. Laparoscopic intrauterine inseminations were conducted 54–60 h after CIDR removal. The number of CL's and pregnancy diagnosis was recorded using ultrasonography 7 and 54 days following AI, respectively. Half of ewes in control group and most of the ewes treated with eCG showed signs of estrus within 36 h of CIDR removal. The ewes in groups G750 and G850 recorded the highest number of large follicles at estrus and CL's 7 days later. The pregnancy rate in groups G550 (75.0%) and G650 (75.0%) was higher (P < 0.05) than that in the other groups. The ovarian response and estradiol concentration, as well as pregnancy rate showed that 550 or 650 IU eCG treatment is the most effective doses in improving the pregnancy rate in Iranian Chall ewes.     

Estrus synchronization in beef cows: comparison between GnRH+PGF2alpha+GnRH and PRID+PGF2alpha+eCG

The aim of this study was to compare two protocols for estrus synchronization in suckled beef cows over a 2 years period. The population studied consisted of 172 Charolais and 168 Limousin cows from 12 and 14 beef herds, respectively. In each herd, cows were allotted to groups according to parity, body condition score and calving difficulty. Cows in Group 1 (n=174) received PRID on Day-8 with estradiol benzoate (10mg, vaginal capsule), dinoprost on Day-4 (25mg i.m.), eCG on Day 2 (500 IU i.m.). The PRID was removed on Day-2 and cows were inseminated on Day 0, 56 h after PRID was removed. Cows in Group 2 (n=166) received GnRH on Day-10 (100 microg i.m.), dinoprost on Day-3 (25mg i.m.) and GnRH on Day-1 (100 microg i.m.), and were inseminated on Day 0, 16-24h after the last GnRH treatment. Plasma progesterone concentrations were measured to determine cyclicity prior to treatment (Days-20 and -10), to confirm the occurrence of ovulation (Days 0 and 10) and to determine the apparent early pregnancy rate (Days 0, 10 and 24). Pregnancy diagnosis was performed by ultrasonography between Days 35 and 45. The effects of various factors on ovulation, apparent early pregnancy and pregnancy rates were studied using logistic mixed models. There was no significant difference between Groups 1 and 2, respectively, for the cyclicity rate before treatment (80.5% versus 80.1%), for apparent pregnancy rate on Day 24 (62.1% versus 54.8%, P=0.09) and for pregnancy rate on Days 35-45 (53.8% versus 46.3%, P=0.16). Ovulation rate was higher (P<0.01) in Group 1 (90.8%) than in Group 2 (77.1%) and was affected by cyclicity prior to treatment in Group 2 but not in Group 1 (Group 1: 88.2% in anestrous cows versus 91.4% in cyclic cows; Group 2: 45.5% in anestrous cows versus 85.0% in cyclic cows, P interaction=0.05). Apparent pregnancy rates on Day 24 were influenced by the year of study (52.4% versus 68.8%, OR=2.12, P<0.01) and by the cyclicity before treatment (anestrous cows 46.3% versus cyclic cows 61.5%, OR=1.86, P<0.05). Pregnancy rates at 35-45 days were influenced by the year of study (44.2% versus 59.8%, OR=1.92, P<0.01). In conclusion, although pregnancy rates were similar for the two treatments, the combination of GnRH+PGF2alpha+GnRH in suckled beef cows induced a lower rate of ovulation than treatment with PRID+PGF2alpha, particularly in anestrous cows.     

Endocrine events during the periestrous period and the subsequent estrous cycle in ewes after estrus synchronization

The aim of the present study was to investigate the endocrinology of the periestrus period and that of the subsequent estrous cycle in ewes synchronized during the breeding season. Animals were treated for 14 days with either MAP intravaginal sponges or subcutaneous progesterone implants, followed by administration of 500 IU PMSG at the time of withdrawal. The time to estrus occurrence following progestagen withdrawal differed significantly between groups (45.3+/-2.7h for the MAP and 21.5+/-1.2h for the implant group, P<0.001). Estradiol levels around estrus did not differ between groups, but a significant difference was detected for the interval from peak estradiol to estrus, with a shorter interval for the implant group (26.7+/-0.7 and 2.7+/-0.9h, P<0.001). Progesterone implants shortened the interval from removal to LH surge, compared to the MAP group (31.2+/-4.4 and 56.5+/-3.6h, respectively, P<0.05). An earlier response was also observed for the interval from estradiol peak to LH peak in the implant group (12.1+/-3.3 and 37+/-2h, respectively, P<0.005), but no difference was observed for the interval from estrus to LH surge. Progesterone levels, particularly during the Days 6 to 10 of the subsequent estrous cycle were significantly higher (P<0.05) in the implant group. It is concluded that the kind of progesterone treatment may affect the time of estrus and the LH peak as well as the progesterone levels of the subsequent cycle.     

The effect of vitamin E treatment during preovulatory period on reproductive performance of goats following estrous synchronization using intravaginal sponges

The objectives of this study were to investigate whether the use of intravaginal sponge for estrous synchronization of goats causes oxidative stress, and to examine the effect of administering vitamin E during preovulatory period on reproductive performance of estrous synchronized goats. Estrus was synchronized in 36 non-lactating adult does using intravaginal sponges containing 30 mg of fluorogestane acetate (FGA) for 14 days. All females received 500 IU of eCG at the sponge withdrawal. The goats were allocated at random to two groups balanced for breed, age and body weight. Treatment group (n=18) received 200mg of vitamin E i.m. at the time of sponge removal and again at the time of second artificial insemination. The other 18 goats (control) were administered 1 ml of physiological saline instead of vitamin E on each of these two occasions. All does in estrus was intracervically inseminated at 12 and 24h after the onset of estrus. Blood samples were collected every 72h during the experimental period for evaluation of malondialdehyde (MDA) and vitamin E concentrations. Serum MDA level increased and vitamin E concentration decreased during the period of vaginal sponge application. Following the sponge removal, MDA level declined rapidly to below basal level in the treatment group but remained high in the control group. Conversely, vitamin E concentration increased in the treatment group after the sponge withdrawal and remained at a low level in the control group. No statistically significant differences (P>0.05) were observed between groups in terms of estrous response, conception rate, gestation length or kidding rate. However, the number of multiple births (70.0% versus 50.0%) and prolificacy rate (2.40+/-0.37 versus 1.63+/-0.26 kids per kidding) were significantly higher (P<0.05) for the treatment group than those of the control group. The results indicate that the use of intravaginal sponges for estrous synchronization of goats causes an increase in level of oxidative stress. However, the vitamin E treatment during preovulatory period can prevent the overproduction of reactive oxygen species (ROS), and it may improve the multiple birth rates and the number of kids born in estrous synchronized goats.     

Corpus luteum function following single and double ovulation during estrous cycle in Sanjabi ewes

This study compared the effect of double and single ovulation on serum progesterone concentrations and luteal characteristics in Sanjabi ewes at different days of the estrous cycle. The estrous cycles of 197 Sanjabi ewes were synchronized by a 12-day treatment with intravaginal sponges (Chronogest^®). Estrus was detected in 144 ewes 27–39 h after sponge removal. Daily blood samples were taken every morning and analyzed for serum progesterone (P4). Ewes were then transported to a local abattoir, where nine ewes were slaughtered on each experimental day (days 1–16 after estrus) for ovary collection. The ovarian follicles were measured and categorized by size (very small <2 mm; small 2–3.5 mm; medium 3.5–5 mm; large >5 mm). On each slaughter day, the number of corpora lutea per ewe was classified as single and double ovulation. The results show that the effect of dominant follicles was less during the mid-luteal phase. Ovulation rate of right, left and both ovaries were (54.9%), (23.6%) and (21.5%), respectively. The incidence of double ovulations was 40.2%. In the case of ewes exhibiting double ovulation, 46.6% occurred unilateral (ewes exhibited both ovulations on the right ovary); whereas 53.4% occurred bilateral (ewes exhibited ovulations on the right and left ovaries). Unilateral double ovulation was not observed in the left ovary. The right ovary appeared to play a significantly greater role in ewes showing single and double ovulations than the left ovary (P < 0.05). Serum progesterone concentration showed minimum and maximum levels of 0.29 ± 0.15 and 5.51 ± 0.75 ng/ml on days 16 and 11 post-estrous, respectively (P < 0.001). The mean volume of individual corpus lutea in ewes with single ovulations was significantly higher than in ewes with double ovulations (P < 0.01). However, the total volume of corpus lutea in ewes with single ovulation was significantly lower than in ewes with double ovulations in some days of estrous cycle (P < 0.01). The serum progesterone concentration was significantly higher in double than single ovulating animals on days 1–16 of the estrous cycle (P < 0.001). These results indicated a relatively high incidence of double ovulation in ewes associated with increasing total luteal volume and high circulating concentrations of progesterone.     

Regulation of the estrous cycle in ewes with progestin containing implants: Influence of dose and day of cycle at treatment

Implants containing Norgestomet (G. D. Searle and Co., Chicago) were inserted subcutaneously in ewes on selected days of the estrous cycle. When ewes were treated for 13 days with 2 or 3 mg Norgestomet, implantation 13 days post-estrus reduced the number of ewes in estrus within 5 days of implant removal and reduced the number of estrous ewes that lambed compared with ewes implanted 4 days post-estrus. When ewes were implanted with 3 or 6 mg Norgestomet 4 or 13 days post-estrus, no difference in estrus response was found. Conception rate was not influenced by day of treatment, but was higher in those ewes treated with 6 mg than ewes treated with 3 mg. Compared to no treatment, treatment with 3 or 6 mg Norgestomet reduced the number of uterine and oviducal sperm recovered 12 or 24 hr after insemination from ewes implanted for 12 days 2 or 12 days post-estrus. However, more sperm were recovered from ewes treated 2 days than 12 days post-estrus with the principal increase occurring in ewes treated with 6 mg of Norgestomet.     

The influence of exogenous progestin on the occurrence of proestrous or estrous signs, plasma concentrations of luteinizing hormone and estradiol in deslorelin (GnRH agonist) treated anestrous bitches

The objectives of this study were to confirm: (i) whether progestin treatment suppressed GnRH agonist-induced estrus in anestrous greyhound bitches; and (ii) the site of progestin action (i.e. pituitary, ovary). All bitches received a deslorelin implant on Day 0 and blood samples were taken from -1 h to +6 h. Five bitches were treated with megestrol acetate (2 mg/kg orally once daily) from -7 d to +6 d (Group 1) and 10 bitches were untreated controls (Group 2). Proestrous or estrous signs were observed in 4 of 5 bitches in Group 1, and 4 of 10 bitches in Group 2 (P = 0.28). The plasma LH responses (area under the curve from 0 to 6h after implantation) were higher (P = 0.008) in Group 2 than in Group 1. Plasma LH responses were similar (P = 0.59) in bitches showing signs of proestrus or estrus (responders) and in non-responders. The plasma estradiol responses (calculated as for LH response) were greater in Group 1 than in Group 2 (P = 0.048), and in responders than in non-responders (P = 0.02). In conclusion: (i) progestin treatment (a) did not suppress the incidence of bitches showing deslorelin-induced proestrus or estrus, and (b) was associated with a reduced pituitary responsiveness and an increased ovarian responsiveness to deslorelin treatment; (ii) the occurrence of proestrous or estrous signs reflected increased ovarian responsiveness to induced gonadotrophin secretion and not increased pituitary responsiveness to deslorelin.     

The effect of progestin and GnRH treatments on ovarian function and reproductive hormone secretions of anestrous postpartum suckled beef cows

Eighteen anestrous crossbred suckled beef cows were assigned to one of three treatment groups. Treatments were as follows: Group 1 cows (n = 3) were untreated and served as controls, Groups 2 cows (n = 6) were intramuscularly administered 250 mug GnRH, and Group 3 cows (n = 9) were subcutaneously administered a progestin ear implant for eight days prior to the administration of 250 mug GnRH. The GnRH was given to cows in Group 3 24 h after the time of progestin implant removal. Cows were 21 to 31 days postpartum at the time of GnRH treatment. The percent of cows that ovulated after the time of GnRH treatment was 0%, 83% and 100% for Groups 1, 2 and 3, respectively. For the cows that ovulated, more (P < 0.05) cows in Group 2 (80%) had abnormal luteal phases than in Group 3 (33%). The GnRH-induced LH release and peak LH concentrations were greater (P < 0.01) in the cows in Group 3 (214.3 +/- 37.1 ng/ml) than in the cows in Group 2 (142.7 +/- 19.0 ng/ml). The LH concentrations of the control cows remained very low throughout the sampling period. Although prostaglandin metabolite (PGFM) concentrations were not significantly (P > 0.10) different among groups, mean concentrations were higher and more variable for cows in Groups 1 (39.2 +/- 5.2 pg/ml) and 2 (39.4 + 6.1 pg/ml) than for cows in Group 3 (25.1 + 1.4 pg/ml).     

Ovarian superstimulation after follicular wave synchronization with GnRH at two different stages of the estrous cycle in cattle

The objective of this study was to evaluate superovulatory programs based on synchronization of follicular waves with GnRH at 2 different stages of the estrous cycle. Sixteen Holstein cows were randomly assigned to 1 of 3 groups and administered GnRH (Cystorelin, 4 ml i.m.) between Days 4 and 7 (Groups 1 and 3) or between Days 15 and 18 (Group 2) of the estrous cycle (estrus = Day 0). Four days after GnRH treatment, > or = 7-mm follicles were punctured in Groups 1 (n = 6) and 2 (n = 6) or were left intact in Group 3 (n = 4). All cows were superstimulated 2 d later (i.e., from Days 6 to 10 after GnRH treatment) with a total of 400 mg NIH-FSH (Folltropin-V) given twice daily in decreasing doses. The GnRH treatment caused a rapid disappearance of large follicles (P < 0.005), rapid decrease in estradiol concentrations (P < 0.003), and increase in the number of recruitable follicles (4 to 6 mm; P < 0.04), indicative of the emergence of a new follicular wave within 3 to 4 d of treatment. Between 4 and 6 d after GnRH treatment, the mean number of 4- to 6-mm follicles decreased (4.7 +/- 1.8 to 1.5 +/- 3.3) in the nonpunctured group but increased (3.9 +/- 1.0 to 7.3 +/- 1.9) in the punctured group of cows (P < 0.05). In response to FSH treatment, the increase in the number of > or = 7-mm follicles was delayed by approximately 2 d in the nonpunctured group (P < 0.006). Moreover, the mean number of > or = 7-mm follicles at estrus was higher (16.9 +/- 1.7 vs 11.5 +/- 3.0; P < 0.1) in the punctured than the nonpunctured group. The increase in progesterone concentration after estrus was delayed in the nonpunctured group (P < 0.1) compared with the punctured follicles. Mean numbers of CL as well as freezable (Grade 1 and 2) and transferable (Grade 1, 2 and 3) embryos were similar (P > 0.1) in punctured and nonpunctured groups. Spontaneous estrus did not occur prior to cloprostenol-induced luteolysis in any group, and stage of the estrous cycle during which GnRH was given did not affect (P > 0.1) hormonal and follicular responses in the punctured groups. In conclusion, GnRH given at different stages of the estrous cycle promotes the emergence of a follicular wave at a predictable time. Puncture of the newly formed dominant follicle increases the number of recruitable follicles (4 to 6 mm) 2 d later and, in response to superstimulation with FSH, causes a greater number and faster entry of recruitable follicles into larger classes (> or = 7 mm) and a faster postovulatory increase in progesterone concentrations.     

The effect of method of GnRH administration and short-term calf removal on ovarian function and reproductive performance in postpartum suckled beef cows administered PGF(2)alpha for estrous synchronization

The first experiment was a 2 x 2 factorial experiment with calf removal (none or short-term) and method of GnRH administration (intramuscularly in saline or subcutaneously in gelatin capsules) as main effects. The durations of the GnRH-induced LH surges were similar among groups but the LH surges were delayed in the cows that received GnRH subcutaneously in gelatin capsules. Calf removal enhanced the GnRH-induced LH release for cows administered GnRH subcutaneously in a gelatin capsule but not for cows administered GnRH intramuscularly in saline. In the second experiment, 191 postpartum suckled beef cows were administered two injections of prostaglandin F(2)alpha(PGF(2)alpha) 11 days apart. After the second PGF(2)alpha injection, the cows were assigned to a 2 x 2 factorial experiment as in Experiment 1 plus one control group. Short-term calf removal (47 h) began 28 h after the second PGF(2)alpha injection. GnRH was administered 30 h after the time of calf removal. The number of cows that ovulated following the time of the GnRH treatment, the number that had abnormal luteal phases and the first-service pregnancy rates among treatment groups within the anestrous and cyclic cows classifications were not significantly different. However, several effects were detected and are reported.     

Comparison of controlled internal drug release device and melengesterol acetate as progestin sources in an estrous synchronization protocol for beef heifers

The objectives of this experiment were to compare estrous synchronization responses and AI pregnancy rates of beef heifers using protocols that included either CIDR or MGA as the progestin source. The hypotheses tested were that: (1) estrous synchronization responses after (a) progestin removal, and (b) PGF(2alpha); and, (2) AI pregnancy rates, do not differ between heifers synchronized with either progestin source. At the start of the experiment (Day 0) in both years, heifers were assigned randomly to receive, MGA supplement for 14 days (MGA-treated; n=79) or CIDR for 14 days (CIDR-treated; n=77). On Day 14 progestin was removed and heifers were observed for estrus up to and after PGF(2alpha) on Days 31 and 33 for CIDR-treated and MGA-treated heifers, respectively. Heifers that exhibited estrus within 60h after PGF(2alpha) were inseminated by AI 12h later; the remaining heifers were inseminated at 72h after PGF(2alpha) and given GnRH (100mug). More (P<0.05) CIDR-treated heifers exhibited estrus within 120h after progestin removal than MGA-treated heifers. Intervals to estrus after progestin removal were shorter (P<0.05) for CIDR-treated heifers than MGA-treated heifers. More (P<0.05) CIDR-treated heifers exhibited estrus and were inseminated within 60h after PGF(2alpha) than MGA-treated heifers. Pregnancy rates did not differ (P>0.10) between MGA-treated (66%) and CIDR-treated (62%) heifers. In conclusion, the use of CIDR as a progestin source in a 14-day progestin, PGF(2alpha), and timed AI and GnRH estrous synchronization protocol was as effective as the use of MGA to synchronize estrus and generate AI pregnancies in beef heifers.     

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.     

Fertility in postpartum dairy cows in winter or summer following estrus synchronization and fixed time AI after the induction of an LH surge with GnRH or hCG

In this study, the fertility of postpartum dairy cows after a sequence of treatments with GnRH (Day 0), PGF2alpha (Day 7) and GnRH (Day 9) (GnRH group; n = 164) or hCG (Day 0), PGF2alpha (Day 7) and hCG (Day 9) (group hCG; n = 166) was investigated in summer and winter seasons. All cows were artificially inseminated without estrus detection, 16-18 h after the end of treatment. Control cows (CONT; n = 226) were not treated and were inseminated at natural estrus. The pregnancy rates at Day 90 (46% versus 33%; P < 0.05) and at Day 135 (76% versus 62%; P < 0.05) postpartum were significantly lower in CONT cows in summer compared to winter months but this effect was not observed in the two treated groups. The number of days from calving to conception was significantly lower in GnRH and hCG treatment groups compared to CONT cows in cold months (102 +/- 3.2, 106 +/- 4.2, 126 +/- 3.1, respectively; P < 0.001) and in hot months (112 +/- 3.2, 114 +/- 4.2, 139 +/- 3.1, respectively; P < 0.001). The concentration of insulin was significantly higher in winter (P < 0.001). There were no differences in average plasma concentration of glucose (P = 0.474), GH (P = 0.441) or IGF-I (P = 0.190). In conclusion, we have shown that veterinary supervision combined with a program of estrous synchronization and fixed time insemination can improve fertility of cows suffering heat stress.     

Increased cleavage and blastocyst rate in ewes treated with bovine somatotropin 5 days before the end of progestin-based estrous synchronization

Treatment with bovine somatotropin (bST) during estrous synchronization increased fertility and prolificacy in sheep. In the present study, a single dose of bST 5 days before the end of progestin treatment improved cleavage and embryo development. Stage of estrous cycle was synchronized in ewes (n=32) with progestin and superovulation was induced by use of FSH. Five days before the end of progestin treatment, ewes were randomly assigned to two groups: bST group (n=16) received a depot injection of 125 mg of bST sc (Lactotropina, Elanco, México) and the control group (n=16) received saline solution. Estrous was detected with rams fitted with an apron every 2 h and estrous sheep were mated every 8 h whilst in estrous. Embryos were recovered on Day 7 post mating, assessed microscopically and fixed in 4% paraformaldehyde. Cell number in blastocysts was counted after Hoechst 33342 staining. Plasma concentrations of IGF-I, insulin and progesterone were determined in eight sheep per group from the day of bST treatment to the day of embryo recovery. Cleavage rate, percentage of transferable embryos (transferable embryos/cleaved) and percentage of embryos reaching the blastocyst stage (blastocyst/cleaved) were compared between groups by logistic regression. IGF-I, insulin and progesterone plasma concentrations were analyzed by ANOVA for repeated measurements and cell number by ANOVA. Cleavage rate was greater (P<0.01) in bST treatment group (86%) than in the control group (62%). Similarly, the proportion of embryos reaching the blastocyst stage (bST=68.7 vs control=42.5) and the number of cells per blastocyst (bST group 91.8±5.5 compared to control group 75±6) were greater (P<0.01) in the bST-treated sheep. Plasma concentrations of IGF-I and insulin were greater (P<0.01) in the bST-treated group. No changes were observed in progesterone concentrations (P=0.5). It is concluded that bST injection 5 days before progestin removal increases cleavage rate and the proportion of embryos that reach the blastocyst stage. These effects are associated with an increase in IGF-I and insulin concentrations.     

The effect of type of vaginal insert and dose of pLH on embryo production, following fixed-time AI in a progestin-based superstimulatory protocol in Nelore cattle

The objective was to analyze and report field data focusing on the effect of type of progesterone-releasing vaginal insert and dose of pLH on embryo production, following a superstimulatory protocol involving fixed-time artificial insemination (FTAI) in Nelore cattle (Bos taurus indicus). Donor heifers and cows (n = 68; 136 superstimulations over 2 years) received an intravaginal, progesterone-releasing insert (CIDR or DIB, with 1.9 or 1.0 g progesterone, respectively) and 3-4 mg of estradiol benzoate (EB) i.m. at random stages of the estrous cycle. Five days later (designated Day 0), cattle were superstimulated with a total of 120-200 mg of pFSH (Folltropin-V), given twice daily in decreasing doses from Days 0 to 3. All cattle received two luteolytic doses of PGF2alpha at 08:00 and 20:00 h on Day 2 and progesterone inserts were removed at 20:00 h on Day 3 (36 h after the first PGF2alpha injection). Ovulation was induced with pLH (Lutropin-V, 12.5 or 25 mg, i.m.) at 08:00 h on Day 4 with FTAI 12, 24 and in several cases, 36 h later. Embryos were recovered on Days 11 or 12, graded and transferred to synchronous recipients. Overall, the mean (+/-S.E.M.) number of total ova/embryos (13.3 +/- 0.8) and viable embryos (9.4 +/- 0.6) and pregnancy rate (43.5%; 528/1213) did not differ among groups, but embryo viability rate (overall, 70.8%) was higher in donors with a DIB (72.3%) than a CIDR (68.3%, P = 0.007). In conclusion, the administration of pLH 12 h after progesterone removal in a progestin-based superstimulatory protocol facilitated fixed-time AI in Nelore donors, with embryo production, embryo viability and pregnancy rates after embryo transfer, comparable to published results where estrus detection and AI was done. Results suggested a possible alternative, which would eliminate the need for estrus detection in donors.     

Luteal function and blastocyst development in ewes following treatment with PGF(2)alpha and GnRH

Luteal function and blastocyst development were compared in ewes treated with GnRH (100 mug) on Day 1 (Day 0 = day of estrus) or in ewes previously induced into estrus with PGF(2)alpha. In Experiment 1, the duration of estrous cycles of ewes previously treated with PGF(2)alpha were longer (P<0.06) than those that received PGF(2)alpha plus GnRH, GnRH alone, or remained untreated (control) ewes. Progesterone concentrations were lower (P<0.07) on Day 1 and higher (P<0.01) on Days 16 and 17 of the estrous cycles following PGF(2)alpha treatment relative to those of the natural (control) cycles. In Experiment 2, blastocysts of ewes treated with PGF(2)alpha were less developed (P<0.06) by Day 13 of pregnancy than those of the control ewes. The GnRH treatment did not influence any of these characteristics. Treatment with PGF(2)alpha delayed luteal formation during the subsequent estrous cycle, increased the duration of the estrous cycle and slowed the rate of blastocyst development relative to GnRH-treated and untreated ewes.     

Progesterone treatment, FSH plus eCG, GnRH administration, and Day 0 Protocol for MOET programs in sheep

The effect of various superstimulatory treatments on the number of corpora lutea, fertilization rate, and embryo yield was studied in sheep. Overall, data from 708 Merino donors and 4262 embryos were analyzed in four experiments. In Experiment 1, varying intervals of progesterone treatment (5 to 14 d) before follicle-stimulating hormone (FSH) administration did not significantly affect the proportion of responding donors, the mean number of corpora lutea, or the mean number of recovered and transferable embryos per donor. In Experiment 2, a single dose of equine chorionic gonadotropin (eCG, 200 or 300 IU) combined with the FSH treatment (i.e., given at CIDR removal) reduced the number and the quality of embryos compared with that for not giving eCG (P < 0.05). In Experiment 3, one dose of gonadotropin-releasing hormone (GnRH) given 24 h after CIDR removal improved the number of transferable embryos compared with that for not giving GnRH (P < 0.05). In Experiment 4, the new superstimulatory Day 0 Protocol, which includes starting FSH treatment at the emergence of Wave 1 (i.e., soon after ovulation, in the absence of a large follicle), improved ovarian response, with a tendency to produce more embryos compared with that for the Traditional Protocol. In summary, this study, analyzing data from various pharmacologic treatments, allows an improvement from four to eight transferable embryos per treated donor in multiple ovulation and embryo transfer programs in sheep.     

Ovulation synchronization following commercial application of ultrasound-guided follicle ablation during the estrous cycle in mares

A regimen of progesterone plus estradiol (P&E) was used as a standard for ovarian synchronization to test the efficacy and evaluate the commercial application of ultrasound-guided follicle ablation as a non-steroidal alternative for ovulation synchronization in mares. Recipient mares at a private embryo transfer facility were at unknown stages of the estrous cycle at the start of the experiment on Day 1 when they were randomly assigned to an ablation group (n=18-21 mares) or to a P&E group (n=20-21 mares). In the ablation group, mares were lightly sedated and all follicles > or = 10 mm were removed by transvaginal ultrasound-guided follicle aspiration. In the P&E group, a combination of progesterone (150 mg) plus estradiol (10mg) prepared in safflower oil was given daily (im) for 10 d. Two doses of prostaglandin F(2alpha) (PGF, 10mg/dose, im) were given 12 h apart on Day 5 in the ablation group, or a single dose on Day 10 in the P&E group. Human chorionic gonadotropin (hCG, 2500 IU/mare, im) was given at a fixed time, 6 and 10 d after PGF treatment in the ablation and P&E groups, respectively, with the expectation of a follicle > or = 30 mm at the time of treatment. In both the ablation and P&E groups, transrectal ultrasonography was done at the start of the study (Day 1) and again on the day of hCG treatment and daily thereafter to determine the presence of a CL, measure diameter of the largest follicle and detect ovulation. The mean interval from the start of the study and from PGF treatment to ovulation was shorter (P<0.0001) in the ablation group (13.7 and 9.7 d, respectively) compared to the P&E group (22.3 and 13.2 d, respectively). Following fixed-day treatment with hCG after PGF treatment, the degree of ovulation synchronization was not different (P>0.05) between the ablation and P&E groups within a 2-d (56 and 70%) or 4-d (83% and 90%) period. Although ultrasound-guided follicle ablation may not be practical in all circumstances, it excluded the conventional 10-d regimen of progesterone and estradiol and was considered an efficacious and feasible, non-steroidal alternative for ovulation synchronization in mares during the estrous cycle.