Concentrations of fat and plasma 5 -androstenone and plasma testosterone in boars selected for rate of body weight gain and thickness of back fat during growth, sexual maturation and after mating

Abstract

The levels of 5.alpha.-androstenone and testosterone in peripheral plasma and 5.alpha.-androstenone in fat collected from 18 boars selected according to thickness of back fat and rate of gain were evaluated. Sampling was started when the animals were about 100 days of age and samples were collected every 14 days until the boars were about 240 days old. The steriod profiles varied considerably between boars, although an increase in steroid levels was found in most animals with the onset of adolescence. The regression line for the level of 5.alpha.-androstenone in fat and the age of the animals in days was y = 0.02x-1.31. High coefficients of correlation were found between the concentration of 5.alpha.-androstenone in peripheral plasma and fat (r = 0.78) and between levels of 5.alpha.-androstenone and testosterone in peripheral plasma (r = 0.64). Levels of 5.alpha.-androstenone in peripheral plasma above about 15 ng/ml were usually accompanied by a heavy accumulation of 5.alpha.-androstenone in adipose tissue. The use of 4 of the boars for mating resulted in increased steriod levels in peripheral plasma and fat. Significantly higher levels of 5.alpha.-androstenone and testosterone were found in the peripheral plasma of boars selected for fatness and a low rate of gain than in boars selected for low back-fat thickness and a high rate of gain.