Estrus detection and subsequent reproduction in dairy cows continuously housed indoors.

Records (1554) from 961 cows continuously housed indoors in two types of barns were analyzed for occurrence and detection of estrus and subsequent reproduction. Variables, percentage of cows observed in estrus by 55 days postpartum, days to first recorded estrus and first service, conception rates, service intervals, days open, and services per conception were analyzed by least squares procedures for year of calving, month of calving, genetic line, barn-type-parity subclasses, and interaction of month by line. A higher percentage of multiparous cows in the tie-stall barn (60%) were observed in estrus by 55 days postpartum than those in the loose-housing barn (50%). Days to first recorded estrus and to first service, 54 and 81, were less for tie-stall cows than for loose-housing cows, 66 and 91. Conception rates at first service and overall conception, 54 and 91%, were higher for tie-stall cows than for loose-housing cows, 42 and 80%. A higher percentage of primiparous cows (69%) was in estrus by 55 days than multiparous cows (55%). Days to first estrus and first service were less for primiparous cows, 47 and 70, than multiparous cows, 60 and 80. Days open were less for primiparous cows. Primiparous cows required 1.9 services per conception compared with 1.7 for multiparous cows.