Yearling Bulls Shorten the Duration of Postpartum Anestrus in Beef Cows to the Same Extent as Do Mature Bulls

摘要: The objective of this study was to determine whether yearling bulls, when pastured with cows, reduced the duration postpartum anestrus same extent as did mature bulls. This experiment conducted over a 3-yr period. Cows were stratified by parity group achieve 37% 2-yr-old and 63% (> 2-yr-old) cows within each treatment (approximately 50 per year). assigned in order which they calved one three groups: 1) isolated from bulls (NBE; n = 158); 2) exposed that > 3 yr age (MBE; 154); or 3) 1 (YBE; 152). Beginning 2nd wk after calving, either sterile (YBE) (MBE) (three group). Blood samples collected twice weekly late March until mid-July year. serum concentrations progesterone ng/mL for two consecutive sampling periods assumed have initiated estrous cycles calving. Duration (YBE 61.8 +/- 1.8 d) not differ (P .10) (MBE 59.5 1.7 d). shorter < .01) (MBE+YBE 61.0 than (NBE 72.3 d).(ABSTRACT TRUNCATED AT 250 WORDS)