Effects of Serum Treated Semen, Bulls, and Herdsmen-Inseminators on Conception to First Service in Large Commercial Dairy Herds

Abstract

Semen from each of 10 Holstein bulls was extended to 15 x 10 6 total spermatozoa per dose in egg yolk-Tris and in egg yolk-Tris containing 20% (vol/vol) heat-treated heifer serum. Semen was used during 12 mo by 11 herdsmeninseminators in four commercial dairy herds to inseminate 2820 Holstein cows on the first postpartum service. Percentage conception of cows free of clinical disorders at breeding was determined by rectal palpation at 30 to 60 days after insemination. Addition of serum to the extender did not influence percentage conception. A significant interaction of bull x seminal treatment was found. Least squares means of percentage conception to first service ranged from 45.3 to 59.9% among the 10 bulls. When bulls were classified as either high (> 55%), average (50 to 55%), or low conception