Richard A. Fayrer-Hosken

Possible mechanisms of mammalian immunocontraception

Ecological and conservation programs in ecosystems around the world have experienced varied success in population management. One of the greatest problems is that human expansion has led to the shrinking of wildlife habitat and, as a result, the overpopulation of many different species has occurred. The pressures exerted by the increased number of animals has caused environmental damage. The humane and practical control of these populations has solicited the scientific community to arrive at a safe, effective, and cost-efficient means of population control. Immunocontraception using zona pellucida antigens, specifically porcine zona pellucida (pZP), has become one of the most promising population control tools in the world today, with notable successes in horses and elephants. A conundrum has risen where pZP, a single vaccine, successfully induces an immunocontraceptive effect in multiple species of mammals. This review describes the most current data pertaining to the mammalian zona pellucida and immunocontraception, and from these studies, we suggest several potential mechanisms of immunocontraception.

Extraction and quantification of acrosin, β‐N‐acetylglucosaminidase, and arylsulfatase‐A from equine ejaculated spermatozoa

Acrosin, Arysulfatase A, and beta-N-acetylglucosaminidase are three key enzymes localized within the mammalian acrosome that play a pivotal role in the penetration of the oocyte. The objectives of this study were to compare two methods of enzyme extraction based on the activities of these enzymes from equine spermatozoa. Method A utilized a 0.5 M Tris-maleate buffer containing 0.1% Triton X-100 and Hyamine 2389. Method B used 0.05 M Tris-HCl, 0.05 M MgCl2 in 0.05 M Tris-maleate, followed by 0.05 M Tris-maleate containing 0.1% Triton X-100. Results indicated that acrosin was initially bound in an acrosin-acrosin inhibitor complex; this complex was dissociated after incubating the extract in 2 mM HCl. Significant (P < 0.001) increases in acrosin activity were found after-acid extraction from 0.076 U/mg after Method B to 0.327 U/mg after Method A. Arylsulfatase A activity was found to have a higher mean activity (P < 0.03) after Method A (0.012 U/mg) as opposed to Method B (0.007 U/mg). Similarly, beta-N-acetylglucosaminidase was found to have a higher mean specific activity (P < 0.001) after Method A (0.037 U/mg) as compared to Method B (0.008 U/mg). This is the first report of the quantification of these enzymes from equine spermatozoa which can ultimately be used as an index of acrosomal damage in cryopreserved semen, and provide additional insight into biochemical alterations between normal vs. abnormal semen.

LEVONORGESTREL IMPLANTS AS A CONTRACEPTIVE IN CAPTIVE WHITE-TAILED DEER

Silastic implants containing levonorgestrel (LNG) were evaluated as a contraceptive in captive white-tailed deer (Odocoileus virginianus). Six adult females and six female fawns received either six or nine implants in autumn. Each implant contained 36 mg of LNG. Blood was analyzed by radioimmunoassay to determine LNG release profile for 5 mo post-implantation. Serum LNG concentrations rose significantly (P = 0.0005) 3 days post-implantation, leveled off after 7 days, and did not change (P = 0.5913) during the remaining 5 mo. Mean (±SE) LNG concentrations for all months were higher (P = 0.0377) in adult and fawn females implanted with nine versus six rods (138.1 ± 14.4 versus 56.7 ± 12.3 pg/ml, respectively). Serum LNG levels did not differ between adults and fawns. Five of the six implanted adult females had normal estrous cyclicity; three of these five adult females became pregnant in the first year. Four implanted females (two yearlings and two adults) were monitored during a second year, and housed with a fertile buck; three of them became pregnant. We do not recommend the use of LNG in deer.

The effects of ergot alkaloids on the breeding stallion reproductive system

REASONS FOR PERFORMING STUDY Ergot alkaloids cause a range of pathological conditions in mares. There is no evaluation of the effects of ergot alkaloids from endophyte-infected tall fescue on the stallion breeding soundness examination spermiogram. OBJECTIVES The objective of this study was to investigate the effect of ergot alkaloids from endophyte-infected tall fescue on the stallions reproductive functions. STUDY DESIGN Crossover toxicology experiment. METHODS Six stallions were fed either toxic endophyte-infected tall fescue seed or a nontoxic endophyte tall fescue seed (Flecha AR-542, MaxQ). The fescue seed content was compounded at 45% of a grain diet and the stallions were fed the grain diet at 1% of their body weight. The stallions were fed the diet for 70 days, then rested for at least 70 days (no fescue seed) and then fed fescue seed for a second 70 days. At regular intervals blood sampling and a breeding soundness examination were performed. RESULTS The mean time to maximal systemic toxicity was 8.33 h after starting toxic seed ingestion with a mean toxicity level of 49.98 ng alkaloid/mg creatinine. After cessation of feeding toxic seed, the systemic alkaloid concentration fell to control levels within 48 h. There were no significant changes in sperm motility, sperm concentration, sperm cell morphology, total number of sperm cells, number of breeding doses, testicular volume, baseline and human chorionic gonadotropin stimulated testosterone levels. There were no changes in core body temperature and superficial scrotal temperature. The ejaculate from stallions consuming endophyte-infected tall fescue seed had significantly lower gel-free volume (47.5 ± 4.1 ml) than stallions consuming nontoxic endophyte tall fescue seed (62.8 + 4.3 ml, P<0.01). CONCLUSION Ergot alkaloids decreased the gel-free volume of stallions consuming high levels of ergot alkaloids but statistically significant effects on the spermiogram of adult breeding stallions were not found.

Anatomy and physiology of the bull's reproductive system.

The control of bovine male reproduction is a finely orchestrated system. However, the mechanism has already been predetermined by the bulls genetic makeup and, to a lesser extent, the environment. Although the endocrine system appears robust, excessive pressures can inhibit or arrest the process. Similarly, structural limits to the bulls anatomy exist, and exceeding them can result in permanent damage. Hence, a thorough understanding of the anatomy and physiology allows successful management of the breeding bull.

Influence of Mating on Duration of Estrus in Captive White-Tailed Deer

Duration of estrus may exceed 24 h in white-tailed deer ( Odocoileus virginianus ). We examined the influence of mating and injected gonadotrophin releasing hormone (GnRH; 100 µg/deer) on duration of estrus. Nine adult females were monitored daily for estrous behavior during autumn and winter 1991–1992 (31 separate estrous cycles). Estrus was assessed using a tractable, epididyectomized adult male. From 13 November 1991 to 3 January 1992 (experiment 1), adult females in estrus were assigned randomly as either control (unbred) or bred to the epididyectomized male. In experiment 2, duration of estrus for females injected with GnRH was compared with unbred females from 2 February 1992 to 23 March 1992. For experiment 1, unbred females were in estrus longer ( P = 0.01) than were females that were bred ( X ± SE ; 2.3 ± 0.3 days versus 1.3 ± 0.2 days, respectively). For experiment 2, duration of estrus for unbred females treated with GnRH did not differ ( P = 0.48) from those that were not bred (1.7 ± 0.3 versus 2.0 ± 0.3 days, respectively). There was no significant ( P = 0.71) change in the duration of estrus for unbred females between the two experiments. Copulation may shorten the duration of behavioral estrus. Administration of exogenous GnRH did not shorten duration of estrus. Prolonged duration of estrus for unbred females may be a mechanism to help ensure all females are bred even in populations with low numbers of males.

Enhanced viability after in vitro fertilization of bovine oocytes matured in vitro with high concentrations of luteinizing hormone*†*Presented at the Forty-Fourth Annual Meeting of The American Fertility Society, October 10 to 13, 1988, Atlanta, Georgia.†Supported by The University of Georgia Veterinary Medical Experiment Station.

The purpose of this study was to better understand requirements for oocyte maturation to yield viable embryos after bovine in vitro fertilization (IVF). High proportions (95% to 100%) of cumulus-surrounded oocytes matured in vitro in all treatments, but subsequent development was enhanced after maturation with high concentrations of purified bovine luteinizing hormone (LH). Beneficial effects of undisturbed cumulus cells were demonstrated. Improved IVF followed insemination of cumulus-surrounded oocytes, but not denuded oocytes, after maturation with high LH (100 micrograms/ml) versus low LH (10 micrograms/ml), implicating cumulus cells in mediating hormonal enhancement. Oocytes matured with high LH resulted in embryos of superior viability, as reflected by cleavage to 4- to 8-cell stages. Pregnancy resulting from transcervical embryo transfer further documented embryonic viability. These findings should be useful in further development and implementation of reproductive and genetic technologies.