Growth patterns of yearling steers determined from daily live weights

Abstract

Growth patterns for free-ranging yearling steers were quantified from daily live weights obtained with automatic scales which animals entered to obtain drinking water. Forty steers were monitored during each summer grazing period of 1986 and 1987. Frequency of watering and, thus, weighing on the automatic scales averaged 2.4 times/day. Significant (P < 0.01) quadratic relationships between live weight and Julian date were obtained. In 1986, predicted live weight of the steers peaked in late July to early August and then decreased through to the end of the grazing period in September. Live weight of the steers in 1987 followed a similar pattern although the late summer decrease was not as great as in 1986. When animals were periodically weighed using manual procedures, a lower rate of gain was measured in the second half than in the first half of the summer grazing period every year from 1983 through 1987. However, we were unable to specifically identify when these weight changes occurred until the automatic scales were used in 1996 and 1987. The automatic weighing equipment documented substantial within-day live weight variability among steers. This variability changed over the grazing period on a day-to-day basis. Within-day variability must be considered when establishing manual weighing schedules with conventional equipment. Live weight data in conjunction with other measurements will permit development of a more comprehensive animal-plant-climate model.