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The transient increase in gonadotrophin secretion, seen in heifer calves between 6 and 20 wk of age, may be critical for early ovarian follicular growth and for initiation of sexual maturation. We treated heifers with either 3 mg of bLH (n = 5; sc) or 4 mg sc of bFSH (n = 5; sc), every other day, between 8 and 12 wk of age. During the first 17 d of treatment, bovine gonadotrophins caused a reduction in maximum antral follicle size and in numbers of large antral follicles, compared to control heifers (P < 0.05). In 4 of 5 bLH treated heifers and 3 of 5 bFSH treated heifers, the emergence of a large dominant antral follicle was delayed (P < 0.05). At 34 wk of age, follicular dynamics did not differ among groups. Serum concentrations of estradiol were decreased in bFSH and bLH treated heifers at 35 wk of age and in bFSH treated heifers at 25 wk of age compared with that of the controls. Time of first ovulation was delayed in bFSH treated heifers compared with control heifers (P < 0.05;bFSH 59.0 +/- 1.2; control 51.4 +/- 1.8; bLH 56.2 +/- 2.5 wk of age). In summary, treatment of 8-wk old heifers with gonadotrophins every other day disrupted folliculogenesis over a 17-d period, delayed first ovulation (bFSH), and decreased ovarian estradiol production at 25 (bFSH) and 35 (bLH, bFSH) weeks of age.

To determine if concentrations of IGF-I in serum are associated with the ovulation rate or if IGF-I concentrations change during an estrous cycle, blood was collected from ewes of three genotypes in two experiments. In Experiment 1, blood was collected once during the mid-luteal phase of an estrous cycle in nulliparous ewes. In Experiment 2, blood was collected every other day from Day 1 to 19 postestrus in primiparous ewes. Three genotypes of ewes were used in both experiments: Dorset × Rambouillet, Finn × Rambouillet and Booroola Merino × Rambouillet. Ovulation rates in Experiment 1 were 1.35, 1.88 and 2.50 for Dorset × Rambouillet (n=17), Finn × Rambouillet (n=49) and Booroola Merino × Rambouillet (n=28) ewes, respectively. IGF-I concentrations in serum were greater (P

The objectives of this study were to determine if 2-year-old fillies could be used successfully for embryo donors and whether repeated embryo recovery attempts would affect subsequent fertility. Twenty-three (Year 1) and 16 (Year 2) 2-year-old fillies were evaluated as embryo donors. The fillies were teased and palpated daily. When a follicle was palpated, the fillies were inseminated (500 × 106 motile spermatozoa) every other day until ovulation was detected. Nonsurgical embryo recoveries were attempted on Days 5 and 6 (−120 and 144 hours) postovulation for a total of 32 times for 16 fillies (Year 1). No embryos were recovered on Day 5. However, seven embryos were recovered during the subsequent collection on Day 6. Fifty-one additional embryos and 19 degenerated ova were recovered from 120 collection attempts which were performed only on Day 6 (Year 1). Eighteen embryos and eight degenerated ova were recovered from 38 collection attempts on Day 6 in Year 2. Mean collections per filly were 8 (range 3 to 16) and 2.69 (range 1 to 4) for Years 1 and 2, respectively. No differences (P>0.05) were found in the interval from collection (prostaglandin injection) to the first day of estrus or from the first day of estrus to ovulation for the collection periods during either year. Moreover, no differences (P>0.05) were found in the interval between collections within or between years. The influence of repeated embryo recovery on subsequent fertility was studied using eight fillies which had undergone collections a mean of 12 times in Year 1. Five of the eight fillies conceived during the first estrous cycle and the remaining three conceived during the second cycle. All fillies produced normal healthy foals and were rebred on the first or second estrous cycle postpartum. These results indicate that repeated embryo recovery attempts yield multiple embryos and do not compromise the subsequent reproductive performance of 2-year-old fillies.

The Catalonian donkey breed is in danger of extinction, and much needs to be learned about the reproductive features of its females if breeding and conservation programmes are to be successful. This study reports the oestrous behaviour, oestrus cycle characteristics and dynamic ovarian events witnessed during 50 oestrous cycles (involving 106 ovulations) in 10 Catalonian jennies between March 2002 and January 2005. These jennies were teased, palpated transrectally and examined by ultrasound using a 5 MHz linear transducer-daily during oestrus and every other day during dioestrus. Predictors of ovulation were sought among the variables recorded. The most evident signs of oestrus were mouth clapping (the frequent vertical opening and closing of the mouth with ears depressed against the extended neck) and occasional urinating and winking of the vulval lips (homotypical behaviour). Interactions between jennies in oestrus were also recorded, including mounting, herding/chasing, the Flehmen response, and vocalization (heterotypical behaviour). Nine jennies ovulated regularly throughout the year; one had two anovulatory periods (54 and 35 days). The length of the oestrus cycle was 24.90 +/- 0.26 days, with oestrus itself lasting 5.64 +/- 0.20 days (mean +/- S.E.M.) and dioestrus 19.83 +/- 0.36 days. The incidence of single, double and triple ovulations was 55.66% (n=59), 42.45% (n=45) and 1.89% (n=2), respectively. No significant difference was seen in the number of ovulations involving the left and right ovaries (52.63% [n=70] compared to 47.37% [n=63] respectively; P0.05). The mean interval between double ovulation was 1.44 +/- 3.98 days. The mean diameter of the preovulatory follicle at day -1 was 44.9 +/- 0.5 mm; the mean growth rate over the 5 days before ovulation was 3.7 mm/day. Data on preovulatory changes in oestrous behaviour, follicle size, follicle texture, the echographic appearance of the follicle and uterus, and uterine tone were subjected to stepwise logistic regression analysis to detect predictors of ovulation. The logit function showed the best predictors to be follicle size, follicular texture and oestrous behaviour. Certain combinations of these three variables allow the prediction of ovulation within 24 h with a probability of75%.

Serum progesterone concentrations and behavioral estrus were determined in two groups of 17 mixed breed dairy does at the beginning of the breeding season. The treatment group was pastured adjacent to two mature bucks while two teaser bucks ran with the group. The control group was pastured without exposure to bucks. Goats were observed for estrus daily for 35 days and samples of jugular blood were collected every other day for radioimmunoassay of progesterone. Signs of estrus were observed in 16 of 17 does in the treatment group within a mean ± S.E. of 5.5 ± 1.3 days after introduction of the bucks. Thirteen does demonstrated a progesterone profile characteristic of a normal estrous cycle with peak progesterone concentrations of 5.9 ± 0.5 ng/ml. Signs of behavioral estrus were not observed in the control group. One control doe demonstrated a progesterone profile characteristic of a normal estrous cycle attaining a peak progesterone concentration of 3.9 ng/ml. Progesterone concentrations in the remaining 16 control does were at or near the lower limits of sensitivity of the assay for the duration of the experiment. Fifteen of the control does exhibited estrus within 7 ± 1.5 days after exposure to bucks at the end of the experiment. These results clearly demonstrated a profound influence of the male on estrous cycle activity during the beginning of the breeding season.

Two pony mares were administered 150 mg of testosterone propionate every other day for 20 days (ten injections) and every ten days there-after. An additional two mares and one stallion were not treated and served as controls. Testosterone propionate was dissolved in absolute ethanol and administered subcutaneously. Sex behavior tests were conducted 26 and 40 days after the first injection. Control mares exhibited very little male sex behavior. Both testosterone propionatetreated mares, however, exhibited mounting, sniffing, flehmen, biting and vocalization behavior in the presence of an estrous mare. The testosterone propionate-treated mares mounted and bit estrous mares more frequently than the stallion but exhibited less sniffing, flehmen and vocalization behavior in the presence of an estrous mare than the stallion. Testosterone propionate-treated mares and the stallion mounted an estrous mare 23.3 +/- 9.7 seconds and 172.5 +/- 22.5 seconds, respectively, after being introduced into the pen. Mares in estrus were mounted by the testosterone propionate-treated mares and the stallion an average of 4.0 +/- 1.3 and 1.0 +/- 0 times, respectively, during a ten-minute test. None of the non-estrous mares was ever mounted by the testosterone propionate-treated mares. In summary, testosterone propionate induced male sex behavior in intact mares and the testosterone propionate-treated mares effectively detected estrous mares.

Two ewes were administered testosterone propionate and subsequent plasma testosterone concentrations determined and male sex behavior recorded. Initially ewes were administered 50 mg of testosterone propionate every other day for 20 days. Within 6 days following the first injection, concentrations of testosterone in plasma increased to 8.0 to 10.0 ng/ml. A 50 mg injection of testosterone propionate administered every 10 days thereafter maintained concentrations of plasma testosterone at 1.0 to 3.0 ng/ml. Sex behavior tests conducted with non-estrus and estrus ewes showed that both testosterone treated ewes developed male sex behavior similar to a ram. Ewes in estrus were mounted by testosterone treated ewes an average of 6.7 ± 1.2 times during a 10 minute test whereas none of the non-estrus ewes were ever mounted. Silastic implants containing testosterone propionate placed in the ewes 83 days following the first injection maintained concentrations of plasma testosterone at 6.0 to 8.0 ng/ml for a 20 day period. Therefore, administration of testosterone propionate to ewes effectively stimulates male sex behavior and would obviate the necessity for vasectomized rams for estrus detection.

Forty-one postpartum anestrous Hereford cows, maintained under range conditions, were used to determine the influence of gonadotropin releasing hormone (GnRH) or pregnant mare serum gonadotropin (PMSG) on ovarian function. Anestrous cows were identified by estrous detection with sterile bulls and concentrations of progesterone in plasma obtained weekly. At 45+/-2 days postpartum, cows were allotted to the following treatments: (1) control (saline), (2) 100 microg GnRH, (3) 200 microg GnRH, (4) 200 microg GnRH in carboxymethyl cellulose (CMC), (5) 500 IU PMSG, (6) 1,000 IU PMSG or (7) 2,000 IU PMSG. Cows were bled frequently the first day after treatment and then every other day until 85 days postpartum. The LH responses after 100 and 200 microg of GnRH were not significantly different and mixing 200 microg GnRH with CMC before injection did not significantly alter the LH response. During the first 20 days after treatment, neither GnRH nor 500 IU PMSG altered estradiol concentrations in plasma, but treatment of cows with 1,000 or 2,000 IU PMSG resulted in increased (P0.01) concentrations of estradiol. The time postpartum required for concentrations of progesterone in plasma to exceed 1 ng/ml was reduced (P0.05) by all treatments except 100 microg GnRH. These data indicate that GnRH causes LH release in anestrous range cows and that treatment with 1,000 or 2,000 IU PMSG initiates ovarian activity as evidenced by increased concentrations of estradiol in plasma.

Two gilts were administered testosterone propionate and their subsequent plasma testosterone concentrations and male sex behavior were recorded. These were compared to testosterone concentrations and male sex behavior in boars. Testosterone propionate (75 mg) was administered to the gilts every other day for 20 days (induction scheme) and every 10 days there-after (maintenance scheme). Concentrations of testosterone in plasma were elevated to concentrations detected in the boars during the induction scheme. During the maintenance scheme, concentrations of testosterone appeared to be lower than in boars. At 20, 30 and 40 days following the first injection, sniffing, nosing and mating song behaviors were exhibited by the testosterone treated gilts similar in frequency to the boars. Mounting behavior was first detected 30 days following the first testosterone propionate injection, and by day 40, the frequency of mounting was greater than observed in boars.

Over a three year period 8 cows and 2 heifers were administered testosterone via injections and/or silastic implants. During and subsequent to treatments, blood samples were collected for determination of testosterone and cows were observed for male sex behavior. Male sex behavior was induced by administering 200 mg of testosterone propionate every other day for 20 days, and once induced, male sex behavior was maintained by injections of 200 mg of testosterone propionate every 10 days or by two 15 cm silastic implants containing testosterone propionate. Male sex behavior was also induced and maintained by administering an injection of testosterone enanthate (1 gm) and testosterone propionate (200 mg) and two 15 cm silastic implants containing testosterone propionate at the same time. Cows which are administered testosterone in this manner detected 94% of 231 females that were in estrus 342 times.

A technique for rapid and repeated laparoscopic ovarian examination was developed for use in the sheep. A midventral approach was used on ewes under general anesthesia on a 45-degree sloped table. Examination could be done as often as every other day. The technique was used for detection of ovulation in studies of gonadotropin stimulation in anestrous ewes. Ovulation was induced with 5 to 10 mg FSH and 100 to 2000 iu HCG. The use of laparoscopy in pregnancy diagnosis was also investigated. Accurate diagnosis could be made by Day 17 using both uterine and ovarian characteristics. Visualization through the laparoscope was utilized for aspiration of follicular oocytes using a 23 ga, 11 cm needle.