Fertility of Cattle Inseminated with 12, 24 or 35 Million Sperm in 0.5 or 0.9 Milliliter

Cows were inseminated with] 2, 24, or 35 million sperm extended to 0.5 or 0.9ml in egg-yolk citrate or Plus-EX and frozen in 1.0ml ampules. The average 60- to 90day nonreturn rate of 73.2% for 9,696 cows inseminated with 0.9ml semen was significantly greater than the fertility (70.5%) of 11,119 cows inseminated with 0.5ml semen (P similar or equal to 0.02). Sperm numbers of 12, 24, and 35 million per ampule resulted in average fertilities of 70.6, 72.0 and 73.1% (P similar or equal to 0.50). Plus- EX resulted in an average of 2.4 percentage points higher fertility than yolk-citrate (P < 0.05). Among the two-way interactions between volumes, extenders, and sperm numbers, only that between volumes and sperm numbers was significant-24 million sperm resulted in highest fertility in 0.9ml and lowest fertility in 0.5ml (P < 0.01). Only the interaction between bulls and sperm numbers was significant (P similar or equal to 0.03) among the 7 interactions between bulls and volumes, extenders, or sperm numbers.