Evidence exists to suggest detrimental effects of heat stress on male fertility. This study was designed to assess the effects of scrotal heat stress on mature and developing sperm in a mouse model. After receiving shock heat treatment (42 degrees C for 30 min), mature spermatozoa were recovered from the epididymis hours (6) or Days (7, 14, 21, 28, 60) later, to determine the variables: number of spermatozoa, sperm viability, motility and progressive motility, sperm DNA integrity as established by the TUNEL method, embryo implantation rate, and sex ratio of the fetuses conceived using the heat-exposed spermatozoa. Our results indicate that transient mild heat treatment does not affect in the same way the different types of male germ cells. Spermatocytes present within the testis at the time of heat stress resulted into a lower concentration of spermatozoa with reduced viability and low motility. Even though, DNA integrity of spermatozoa resulting from spermatocytes was also compromised by heat stress, the higher degree of DNA damage was found among spermatozoa resulting from spermatids present within the testis at the time of heat stress. At last, heat shock effect on spermatozoa present in the epididymis at the time of thermal stress resulted into a sex ratio distortion. These findings point to a higher sensitivity of spermatocytes to heat exposure and also suggest a different response of X and Y chromosome-bearing spermatozoa to heat stress that warrants further investigation.

Scrotal heat stress effects on sperm viability, sperm DNA integrity, and the offspring sex ratio in mice.

Estrous behavior and the estrus-to-ovulation interval in Nelore cattle (Bos indicus) with natural estrus or estrus induced with prostaglandin F2 alpha or norgestomet and estradiol valerate.

The relationship of increased susceptibility of sperm DNA to denaturation and fertility in the stallion.

Two experiments were designed to investigate the endocrine mechanisms by which progestin administration induces puberty in heifers. In experiment 1, prepubertal heifers were randomly assigned by age to receive either a single norgestomet implant for 10 days (NORG ; n = 15) or to serve as unimplanted controls (CONT ; n = 14). Serial blood samples were obtained on Days -0.5, 8.5, and 10.5 (Day 1 = day of implant insertion) and were analyzed for concentrations of LH. On Days 9 and 11, 4 heifers in each treatment were slaughtered, and the reproductive tracts were obtained. Weekly progesterone analyses were performed to estimate the day of puberty in heifers not slaughtered. Puberty was induced in 6 of 7 heifers in the NORG treatment, resulting in an earlier (p 0.10) was observed between treatments in follicular development, uterine weight was greater (p < 0.05) in NORG than in CONT heifers on Day 11. In experiment 2, prepubertal heifers (n = 47) were administered either 1 (1NORG ; n = 16), 3 (3NORG ; n = 16), or 0 (CONT ; n = 15) norgestomet implants for 10 days, and serial blood samples were obtained as described for experiment 1. Transrectal ultrasonography was used to determine the diameter of the largest follicle on Day 9. Plasma samples were obtained after each serial sample collection period and were analyzed for estradiol concentrations. Puberty was induced in 75% (12 of 16) and 81% (13 of 16) of heifers in the 1 NORG and 3NORG treatments, respectively. Four heifers in the 1 NORG treatment, from which serial blood samples were collected, ovulated before removal of the progestin implant, and the LH data for this treatment were deleted. In the 3NORG treatment, LH pulse frequency was suppressed (p < 0.05) on Day 8.5, but was greater (p < 0.05) 12 h after removal of the progestin (Day 10.5) than in the CONT treatment. We conclude that progestin administration hastens puberty by increasing LH secretion after progestin withdrawal and propose that progestin administration induces puberty by accelerating the peripubertal decrease of estradiol negative feedback on LH secretion.

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Progestin-induced puberty and secretion of luteinizing hormone in heifers.

Ergot is caused by a fungus (Claviceps species) which has been found on hundreds of plants in almost every country of the world. The fungus can adapt itself to form many different varieties. New species of the fungus and new hosts are still discovered today. The alkaloids in ergot have caused hundreds of thousands of deaths in the Middle Ages after consumption of contaminated cereal grains, but during the last two decades there has not been a recorded outbreak of ergotism. Grain standards in most countries are very strict and do not permit grain which contains ergot to reach commercial food channels. All involved in cereal grain production and ulilization should be cognizant of the potential danger, however, since ergot contamination at levels above those permitted by grain standards cannot necessarily be detected by the normal evaluation of a flour sample in the cereal chemistry laboratory. There always have been and always will be ergot infections and a possible danger to human health, but man has learned to minimize the potential problem by using proper agricultural practices. Futhermore, techniques for the removal of ergot from contaminated grains have been developed. While human ergotism is a disease of the past, ergotism in animals still occurs frequently. The problem is not a simple one because of many unanswered questions. What is the tolerance of different breeds or species of livestock to ergot? What are the effects of low-level long-term ingestion of ergot on livestock? What is the difference in toxicity to animals of ergot from different cereal ingestion of ergot on livestock? What is the difference in toxicity to animals of ergot from different cereal grain varieties? What is the effect of storage and processing of cereal grain products on the potential ergot toxicity? The last and most important chapter in the history of ergot concerns ergot as a source of pharmacologically useful alkaloids which have found applications in internal medicine and obstetrics. The future promises to bring some new ergot alkaloids and some new uses. Recent research data indicate the possibility of using ergot alkaloids in contraceptives, which would be truly remarkable.

Ergot on cereal grains.

Libido and scrotal circumference of rams as affected by season of the year and altered photoperiod.

Induction of puberty and subsequent reproductive performance.

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Peter J. Burfening

Papers

Libido and scrotal circumference of rams as affected by season of the year and altered photoperiod.

Induction of puberty and subsequent reproductive performance.

Induction of fertile oestrus in prepubertal ewes during the anoestrous season.

Estimates of early embryonic loss in ewes mated to rams selected for high and low prolificacy

Feeding ergot to pregnant ewes