Beta-carotene does not influence fertility in beef heifers

Eighty-four 18-month-old crossbred beef heifers, 3 to 4 months pregnant, were assigned by stratified randomization to either a high or low (control) beta-carotene (B-car) diet to determine the effect of long-term supplementation of B-car on reproductive performance. The heifers were followed through pregnancy, calving and subsequent breeding. The basal diet consisted of barley, canola meal and barley straw. Heifers supplemented by B-car received 625 mg B-car per day in the concentrate. Vitamin A and D complex injections were given monthly to all heifers. Heifers were bred by artificial insemination after Day 60 postpartum. Throughout the study heifers fed the B-car supplement had higher levels of B-car in plasma (> 300 ug/dl) (P < 0.01) than the heifers fed the control diet (< 50 ug/dl). Vitamin A status was satisfactory in all heifers throughout the study. Birth weight of calves, weight gain, and incidence of mortality were not influenced by B-car. For the control and B-car treatments, days postpartum to first normal luteal phase were 67.5 and 62.6 days; days postpartum to first detected estrus were 70.1 and 65.3, and services per conception were 1.24 and 1.29, respectively. Long-term supplementation of B-car increased prepartum plasma progesterone but had no effect on postpartum fertility.