Effects of Heifer Calving Date on Longevity and Lifetime Productivity in Western Canada

The objective of this study is to determine the effect of calving early as a heifer on lifetime production in western Canada. This study evaluated the longevity and life time production data on 211 individual heifers (data gathered for 16 years) at the Western Beef Development Centre (WBDC), Saskatchewan. Heifers were classified as calving in the first (period 1; n= 87), second (period 2; n = 66), or third (period 3; n = 58) 21-day period of the calving season. For each subsequent calf born to the cow, calving period was reassigned in the same manner. The current study showed that the average life time number of calves weaned for heifers that calved in the 1st, 2nd, and 3rd 21-day period was 5.4 ± 0.32, 4.5 ± 0.37, and 4.2 ± 0.39, respectively. Retaining percentage rate of period 1 cows was 4.3-17.8 and 2.1-19.1% units greater than those of period 2 and period 3 cows, respectively. Period 1 heifers had the greatest life time produced total cumulative weaning weight (p <0.01) value of 1157 kg/cow, followed by period 2 and period 3 heifers, 947 and 841 kg/cow, respectively. Period 1 cows generated an additional $718 to $1077 in weaned calf revenues over their lifetime. This study suggested that, in western Canada, heifers that calved earlier had greater pregnancy rates, remained in the herd longer, and produced one more calf in their lifetime than those that calved in the later periods.