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Biomedical subjects

R L Snyder

Publications and source records attributed to R L Snyder.

7 recordsLinked to original sources
PubMed1979

The effect of photoperiod and feed restriction on semen production in the turkey.

In Experiment 1, 72 yearling Broad Breasted White Turkey males were induced to molt under either stimulatory (16L:8D) or nonstimulatory (8L:16D) light used concurrently with a short period of feed and water deprivation, and followed by periods of daily feed restriction (50% of full feed). One-fourth of the males wer killed at intervals of 4, 8, 12, and 16 weeks and their testes weighed. In Experiment 2, 40 yearling Broad Breasted White males were killed at 2-week intervals during an 8-week period of 8 hr light per day followed by a 10-week period of 16 hr light per day. Testes were removed, weighed, and fixed in Bouin's solution for histological preparation. In Experiment 1, birds kept under 16 hr light and given different periods of feed and water deprivation, followed by 8 weeks of feed restriction, failed to terminate semen production, although their testes were reduced substantially in size and function. Other groups of males given 8 hr light per day with concurrent regimens of feed deprivation and daily feed restriction, terminated semen production within 4 weeks. When returned to 16 hr light, the testes were twice as heavy as those of males kept in production during the entire test. In Experiment 2, the testes of birds induced to molt under 8 hr light per day regressed by 73% and 89%, respectively, after 4 and 8 weeks of exposure. When given 16 hr light per day, some spermatogenic activity was noted at 4 weeks, and complete spermatogenesis, with maximum semen production, occurred after 6 weeks. There was evidence that a successful rejuvenation of the testes requires a period of complete quiescence.

Animals↗
PubMed1978

A comparative study of the neurons of origin of the spinocerebellar afferents in the rat, cat and squirrel monkey based on the retrograde transport of horseradish peroxidase.

The cell bodies of the neurons of the spinocerebellar pathways were examined using large injections of horseradish peroxidose into the cerebellum. Sections of each spinal segment were examined with both the DAB and the de Olmos O-dianisidine techniques. Results common to all three species were found. In Clarke's nucleus, the central cervical nucleus, and the spinal border cells there were many heavily labeled cells. Clarke's nucleus was found to project primarily ipsilaterally; the spinal border cells primarily contralaterally; and the central cervical nucleus bilaterally. In addition to these aggregates of spinocerebellar neurons there were numerous labeled neurons scattered throughout the spinal grey. Labeled neurons were found in all portions of the spinal grey except the substantia gelatinosa and lateral cervical nucleus and occurred in all spinal segments. They varied in morphology from large multipolar neurons, found predominantly in the ventral horn to small globular and fusiform neurons that were most abundant in the dorsal horn. These cells were found to project both ipsilaterally and contralaterally. Results common to only two of the species examined were also found. In the dquirrel monkey and the cat, but not the rat, the marginal layer of the dorsal horn in all segments of the spinal contained numerous labeled neurons. These marginal neurons were especially numerous in the squirrel monkey, where as many as 13 to 16 labeled neurons per section of the dorsal horn were found. In the rat and the squirrel monkey but not the cat, some intensely labeled large multipolar neurons were found in the sacral and caudal segments. These are the cells of Stilling's nucleus, a column of cells similar in position and orientation to that of Clarke's column but different in its projections and details of cytoarchitecture. Thus we have not only confirmed that Clarke's nucleus, the central cervical nucleus, and the spinal border cells project to the cerebellum but we have also found several new sources of spinocerebellar afferents.

Animals↗
PubMed1976

Sexual maturity and persistency of lay in the Chukar partridge given stimulatory light at different ages.

In two separate trials, age at sexual maturity (lay of 1st egg) and total eggs laid in a 13-week production period were determined for the Chukar partridge given stimulatory light at 16, 18, 20, 22, 24, 26, 28 or 30 weeks. The best responses occurred with hens given stimulatory light when 26 weeks of age or older. More than 85 percent of these hens laid, and production ranged from 15 to 25 eggs per hen. The youngest age at 1st egg was 161 days, required by one hen given stimulatory light at 16 weeks. Many hens given stimulatory light at 24 weeks or younger failed to lay, and egg production was extremely poor in those that did lay. Based on our results, best egg production can be attained when birds are given stimulatory light at 28 weeks, allowed to lay for 13 weeks, then cycled to lay again when 50 weeks of age. Hens of superior laying ability can be detected in the first cycle of lay, thus reducing the time that would be required to identify these same birds if allowed to lay under natural daylight conditions.

Age Factors↗
PubMed1975

Effect of forced molting on quantity and quality of semen in turkey breeder males as influenced by diet.

Broad Breasted White turkey males were induced to molt by imposing periods of nonstimulatory light and short periods of water and feed deprival starting at 54 weeks of age. Birds kept under 8 or 10 hours of light per day began to molt within 3 weeks, and most had terminated semen production within 4 weeks. When returned to stimulatory light, the birds began to produce semen within 4 weeks and reached peak production within 10 weeks. However, this level of production was lower than the original level attained as young birds. The recycled males produced approximately 20 percent more semen than the males kept under constant stimulatory light, and the semen from the recycled males contained 1 to 2 billion additional sperm per ml. The percentage of normal sperm decreased with increase in age of birds irrespective of light treatment. A skip-a-day-per-week feeding schedule imposed on all males from 54 to 78 weeks of age had no appreciable effect on body weight or efficiency of feed utilization. Also, imposition of feed and water restrictions had no apparent effect on early termination or recovery of semen production.

Animal Feed↗