Testicular vascular cone development and its association with scrotal temperature, semen quality, and sperm production in beef bulls.

The objectives of this study were to characterize development of the testicular vascular cone using ultrasonography and to determine associations of vascular cone morphology with scrotal temperature, semen quality, and sperm production. Beef bulls (n=70) were examined from 10 to 70 wk of age in two years, and a third group of bulls (n=44) was examined only at 74 wk of age. Testicular vascular cone diameter increased until approximately 13.

Effect of improved nutrition during calfhood on serum metabolic hormones, gonadotropins, and testosterone concentrations, and on testicular development in bulls.

The objective of the present study was to evaluate the effects of improved nutrition during calfhood on serum metabolic hormones, gonadotropins and testosterone concentrations, and on sexual development in bulls. Bulls received high (n=17) or control nutrition (n=16) diets from 10 to 30 week of age and the same control nutrition diet from 31 to 74 week of age. Improved nutrition during calfhood resulted in a more sustained period of elevated LH secretion (pulse frequency and total secretion in 10h) during the early gonadotropin rise.

Effect of nutrition during calfhood and peripubertal period on serum metabolic hormones, gonadotropins and testosterone concentrations, and on sexual development in bulls.

The objective of the present study was to characterize the effects of nutrition on circulating concentrations of metabolic hormones, gonadotropins, and testosterone during sexual development in bulls. Nutrition regulated the hypothalamus-pituitary-testes axis through effects on the GnRH pulse generator in the hypothalamus and through direct effects on the testes. Pituitary function (gonadotropin secretion after GnRH challenge) was not affected by nutrition.