Embryo recovery from exercised mares.

The effect of exercise on mare reproductive efficiency was evaluated by comparing rates of embryo recovery from mares assigned to either an exercise regimen or a non-exercise (control) regimen. Exercised mares were worked daily for 30 min under average ambient conditions of >30 degrees C and >50% humidity. Mares were inseminated during estrus and subjected to uterine flush for embryo recovery on d 7 after ovulation for two consecutive cycles. After this, mares were allocated to the opposite group and allowed an estrous cycle without reproductive manipulation; then insemination and uterine flushing were conducted on two more consecutive cycles. Prostaglandin F(2alpha) was administered on the day of uterine flush. Mare rectal temperature increased during exercise from a mean of 38 degrees C to a mean of 39.9 degrees C. Mares had ovulations from smaller follicles when exercised than they did under control conditions (39.8+/-0.5 compared with 41.5+/-0.5mm diameter; P<0.05), and had an increased time from PGF(2alpha) administration to subsequent ovulation (8.47+/-0.337 compared with 9.27+/-0.294 d; P<0.05). Embryo recovery from control mares was 22 of 35 (63%). Fewer embryos were recovered from exercised mares (11 of 32, 34%; P<0.05). The proportion of embryos classified as Grade 1 tended to be less in exercised than in non-exercised mares (4 of 11, 36% compared with 16 of 22, 73%; P=0.051). These data indicate that exercising mares in a hot and humid environment are associated with changes in ovarian follicle development and ovulation, and a reduction in embryo recovery.

Biodegradable estradiol microspheres do not affect uterine involution or characteristics of postpartum estrus in mares.

Quarterhorse mares were used to investigate effects of estradiol-17beta on uterine involution, duration of estrus, interval to ovulation, and fertility achieved by breeding on the first postpartum estrus. On the day of foaling, mares were injected with biodegradable poly (DL-lactide) microspheres containing either 100 mg estradiol-17beta (25 mares) or no drug (27 mares). The treatment period was considered to last for 12 to 15 d. Estrus was determined by teasing mares (n=16) with a stallion. Ovulation was detected by transrectal ultrasonographic examination of ovaries (n=48). On Days 6, 11 and 16 post partum, transrectal ultrasonography was used to measure cross-sectional diameters of the uterine body, uterine horns, and fluid within the uterine lumen (n=28). Uteri were swabbed for bacteriologic culture, and uterine biopsies were obtained from the previously gravid uterine horn on Days 11 and 16 post partum, for assessment of endometritis and morphometric analysis of endometrial histioarchitecture (n=19). Twenty-two mares were bred on foal-heat, and pregnancy was determined by transrectal ultrasonography on 14 to 16 and 30 to 35 d after breeding. With only one exception (diameter of previously gravid uterine horn on Day 11), mean values for all measures of uterine involution did not differ between treatment groups (P > 0.05). No differences were detected between treatment group means for length of estrus or interval to ovulation (P > 0.05). No differences were detected between treatment group liklihoods for recovery of potential bacterial pathogens, presence of endometritis, or presence of intrauterine fluid at 11 or 16 d post partum (P > 0.05). Pregnancy rate of mares treated with estradiol (5 11 ; 45%) was not different from that of control mares (9 11 ; 82%; P > 0.05). Estradiol treatment did not hasten uterine involution, increase duration of estrus, delay ovulation, or increase fertility in these postpartum mares.

Stimulation of renal tubular transport of p-aminohippurate in rats of different ages by treatment with adrenocortical steroids.

Treatment with prednisolone or dexamethasone is followed by an increase in renal excretion of p-aminohippurate (PAH) and in accumulation of PAH in renal cortical slices, particularly in 5- and 10-day-old rats with immature kidney function. Treatment with triamcinolone is effective both in immature and in 55-day-old rats. There is no stimulation of PAH transport after treatment with mineralocorticoids (desoxycorticosterone, aldosterone).

Reproductive performance in mares subjected to examination by diagnostic ultrasound.

Mares were subjected to frequent examination by diagnostic ultrasound and data were compiled with respect to reproductive efficiency. The data were collected over a 3-yr period on 1032 light horse mares. The cummulative pregnancy rate at 35 d post-ovulation was 96.8% and the pregnancy rate per cycle was 76.0% as determined by ultrasound examination. The average number of cycles per conception was 1.43, with an average of 2.29 inseminations per cycle. The incidence of early embryonic death was 7.8%. Mares were subjected to an average of 5.04 scans during the follicular phase of the cycle. The average number of ultrasound examinations per mare (including pregnancy examinations) was 9.99. Although these data were obtained from an experiment that did not use both control and treated mares, there was no indication that preovulatory oocytes or embryos were damaged by routine ultrasound examination. Comparisons with existing data from commercial facilities are difficult to make concerning any improvement in reproductive efficiency resulting from the routine use of ultrasonography, but these data do suggest relative safety in equine reproductive management when ultrasound examinations are conscientiously used.

Fertility of donor mares following nonsurgical collection of embryos.

Embryos were collected nonsurgically on Day 7 or 8 after ovulation from 7 Quarter horse mares using a modified 30-ml Foley catheter to flush the uterine horn ipsilateral to the recent ovulation with 500 ml TCM-199 containing Hepes buffer. After collection, the uteri were infused with nitrofurazone to reduce the chances of infection due to the procedure. Eleven collections from 7 mares resulted in recovery of 9 embryos and nonsurgical transfer of 4 of these resulted in the birth of one foal. After collections, 8 oestrous cycles averages 22.75 days and 2 extended oestrous cycles were 43 and 59 days long respectively. Of 6 mares mated after one or two embryo collections, 5 conceived to a single service and the sixth during the third oestrus in which she was covered.