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One hundred and sixty ewes were assigned to sixteen groups in a 2 × 2 × 4 factoral design and were treated during the anestrous season. The main effects were progesterone pretreatment (non-implanted and implanted for 14 days), PMS pretreatment (no pretreatment and pretreatment with 500 IU at the time of progesterone implant removal) and treatments (none, GnRH in saline, GnRH in gelatin capsules and HCG). GnRH in saline (250 μg) and HCG (500 IU) were administered intramuscularly and GnRH in gelatin capsules (250 μg) was administered subcutaneously 24 hours after the time of progesterone implant removal. Ewes were classified into one of four progesterone response categories: cyclic, transient, prolonged and no response. An injection of GnRH in saline induced a prolonged progesterone response in only one ewe (13%) which was similar to the response in the untreated ewes (0%). More ewes administered GnRH in gelatin capsules (56%) and more ewes administered HCG (89%) had a prolonged progesterone response than GnRH (in saline) treated or untreated ewes. A higher percentage of ewes that were pretreated with PMS and treated with GnRH in saline (78%) had a prolonged progesterone response than ewes treated with either PMS (22%) alone or with GnRH (in saline; 13%) alone.

Beginning in December, pony mares were placed under a schedule of increasing light. Starting in February, onset of estrus was checked by daily teasing with a stallion. Mares were randomly assigned to one of three treatments (6 mares per group) administered in March. Treatments were: Group I — 75 mg progesterone injected intramuscularly every day for 10 days in combination with a 1.25 mg injection of PGF2α on day 7 of progesterone treatment and a 2,000 IU injection of HCG on day 2 of estrus; Group II — a norgestomet ear implant inserted for 10 days in combination with 1.25 mg PGF2α given 7 days after insertion and 2,000 IU HCG administered on day 2 of estrus; and Group III — same as II except that 2 mg of GnRH rather than HCG were administered on day 2 of estrus. Blood plasma for radioimmunoassay of progesterone, LH and estradiol was collected from the first day of treatment until 14 days after the end of estrus. Also in March, 6 mares were bled daily from the first day of estrus until subsequent estrus or day 21 (control estrus). Although estrus was detected in all mares, 14 of 18 mares ovulated subsequent to treatments and four of the six control estrus mares ovulated. Only among HCG treated mares was the ovulation rate higher (P < .05) than it was in the control estrus group. The interval from last progesterone injection or norgestomet implant removal to estrus did not differ between treatment groups. Concentrations of estradiol and LH were increased for several days around the time of ovulation and tended to be positively correlated with each other. In the mares that did not ovulate, concentrations of LH and estradiol appeared to be lower than in mares that ovulated. In summary, progestins in combination with PGF2α and increasing light will synchronize estrus in mares during late winter and HCG will hasten ovulation in some mares.

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.

The aim of this study was to determine if different methods of handling porcine, ovine, bovine and equine blood between collection and centrifugation influence measurable progesterone levels. A 2 × 2 × 5 factorial experiment was conducted for each species with heparin (with or without), temperature of incubation (4 and 22°C) and time of incubation (0, 6, 12, 24 and 48 h) as the main effects. Following centrifugation, plasma and serum samples were stored at −20°C until progesterone concentrations were determined by radioimmunoassay. Method of handling porcine and equine blood between collection and centrifugation did not affect the levels of progesterone. However, heparinized blood held at 4°C resulted in the most consistent levels of progesterone over time. Progesterone levels were fairly consistent across time in the ovine blood by all methods of handling except heparinized blood incubated at 22°C. By 24 h after collection, plasma progesterone concentrations decreased by 50% for the ovine blood incubated at 22°C with heparin. Decreases were detected by all the methods of handling the bovine blood between collection and centrifugation. The rate of decline, however, was considerably faster for blood held at 22°C than blood held at 4°C. At 12–48 h after collection, the concentrations of progesterone averaged only 5% of the time 0 sample for blood incubated at 22°C. In contrast, at least 30% of the progesterone values in the time 0 sample were detected between 12 and 48 h of incubation for the blood held at 4°C.

In the first of two experiments, ovariectomized ewes with silastic implants containing testosterone propionate had higher concentrations of plasma testosterone than ovariectomized ewes with silastic implants containing testosterone (4.0 ± .2 vs .8 ± .1 ng/ml). In the second experiment, one or two 10 cm silastic implants filled with testoster-one propionate increased concentrations of plasma testosterone and induced male sex behavior in ovariectomized ewes similar to plasma testosterone levels and male sex behavior in rams. The interval from initiation of the treatment to the first behavior test in which mounting was consistently observed was 14.4 ± 2.9 days and once mounting behavior was consistently induced, the testosterone treated ewes mounted estrous ewes an average of 10.7 ± 1.3 times during a 10-minute test.

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.