The influence of level of feed intake on sperm-producing capacity of testicular tissue in the ram

Abstract

The experiment examined the effect of supplementing a roughage diet with lupin grain on the capacity of testicular tissue to produce spermatozoa. Changes in testicle size were estimated by comparative palpation. At the end of the experiment the rams were castrated and the morphology of the testes and their capacity to produce sperm were studied. At the highest level of feed intake, liveweight increased by 32% and testicle volume by 67% during the feeding period of 9 weeks.

Rams on a diet that reduced testicle size produced 18 x l0⁶ sperm/g testis per day, and those on a diet that increased testicle size produced 26 x l0⁶ sperm/g testis per day. Those rams whose testes were increasing in size at castration had significantly larger seminiferous tubules, which occupied a significantly greater proportion of the testicle volume, than rams fed on diets that reduced the size of their testes. The variation in rates of sperm production, together with the large differences in testicle weight, resulted in wide differences in total sperm production among rams fed on different diets.