Selection for reproductive rate in females and feeding regimen on testicular traits and epididymal sperm reserves in Rambouillet rams

Abstract

The objectives of this study were to evaluate whether selection for or against reproductive rate in Rambouillet ewes altered testicular and epididymal characteristics in male offspring, and to examine the interaction of post-weaning feeding regimen and selection line on body weights and testicular and epididymal characteristics. Rams were from lines selected for either low or high reproductive rate and from a random-bred control line. At 10 months of age, rams from each line were assigned to one of two feeding regimens, (i) placed on pasture and fed grass hay for duration of experiment (normal plane; NP) or (ii) continued on a pelleted diet for 7 months then combined with NP rams for the duration of experiment (high plane; HP). Testicular and epididymal traits and epididymal sperm reserves were evaluated at the end of the feeding period. Rams on the HP gained weight more rapidly ( P<0.05) and were heavier ( P<0.05) at the end of the experiment than rams on the NP. Selection line or interactions of line with feeding regimen did not affect ( P>0.10) body weights. Selection line, feeding regimen or their interactions did not affect ( P>0.10) scrotal circumference, testicular or epididymal characteristics or epididymal sperm reserves, except that there was a line by feeding regimen interaction ( P<0.05) for caput/corpus epididymal weight. These results indicate that selecting for low or high reproductive rate in Rambouillet ewes or feeding a high plane of nutrition after weaning did not alter testicular or epididymal characteristics of mature male offspring.