Abstract:
(1) Results of large-scale artificial insemination of Merino sheep (2346 ewes) on a private stud are presented, together with data for seven factorial tests designed to determine effects on fertility, following insemination at one or two successive oestrous periods, of season of insemination, milk diluents, age of ewe, individual ram, and frequency of insemination within a single oestrous period. (2) Insemination in the autumn is more effective than in the spring (79.7 v. 54.7 % of inseminated ewes lambed to insemination over two cycles; P < 0.001). (3) Results for maiden ewes in autumn or spring are 15