Studies on the adaptability of three breeds of sheep to a tropical environment modified by altitude VI. The effect of increased light and injections of vitamin A on semen production and sperm characteristics in tropical rams

Abstract

German Merino, Persian Blackhead and indigenous Native rams were exposed to gradually increasing day-length simulated by use of electric light in the night pen. Between February and June experimental day-length increased from 14 hr. 35 min. to 17 hr. whereas natural day-length fell from 13 hr. 50 min. to 12 hr. An additional trial was superimposed on the main experiment to determine the effect of vitamin A injections on reproductive function and on ability to respond to photoperiodic stimuli.