SELECTION FOR REPRODUCTIVE RATE IN FEMALES AND FEEDING REGIMEN ON TESTICULAR TRAITS AND EPIDIDYMAL SPERM RESERVES IN RAMBOUILLET RAMS

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 inter action of post-weaning feeding regimen and selection line on body weig hts and testicular and epididymal characteristics. Rams were from line s 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 assig ned to one of two feeding regimens, (i) placed on pasture and fed gras s 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 dur ation of experiment (high plane; HP). Testicular and epididymal traits and epididymal sperm reserves were evaluated at the end of the feedin g 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. Sel ection line or interactions of line with feeding regimen did not affec t (P>0.10) body weights. Selection line, feeding regimen or their inte ractions did not affect (P>0.10) scrotal circumference, testicular or epididymal characteristics or epididymal sperm reserves, except that t here was a line by feeding regimen interaction (P<0.05) for caput/corp us 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 charac teristics of mature male offspring.