Pattern of Parturition as Affected by Time of Feeding and Prediction of the Time of Day that Parturition Will Occur in Spring-Calving Beef Cows1

To determine if time of feeding affects time of day that parturition occurs and whether beef cattle display a predictable parturition pattern as individuals, calving data from 2 herds of spring-calving beef cows located at the University of Idaho (U of I) and Kansas State University Agricultural Research Center'Hays (KSU-ARCH) were analyzed. Each year, cows at U of I were fed between 0600 and 0800 h, and cows at KSU-ARCH were fed between 1600 and 1800 h. When feed was provided in the morning, parturition occurred randomly throughout the day. However, when cows were evening fed, more cattle gave birth during daylight hours (P < 0.01). The KSUARCH data indicated that cows giving birth during daylight hours tended to display less variation in parturition time than cows giving birth during dark hours. Average time of parturition was determined for each cow, and the difference from the individual's average for each parturition time was calculated. Mean difference from an individual's average time of calving was less than 4.25 h for the U of I data (P = 0.01) and less than 3.00 h for the KSU-ARCH data (P < 0.01). These data suggest that, for the animals examined, evening feeding will result in more daylight births, and the time of day that parturition will occur may be predicted within ± 4.25 h based on the average time of day that an individual had previously given birth. However, alteration of feeding time or other factors may affect the predictability of parturition time.