Effect of beta-carotene supplementation on reproductive performance of dairy heifers

Three trials were conducted to determine the effect of feeding supplemental β-carotene on reproductive performance of Holstein heifers. In each trial, the animals were randomly assigned to either a control or treatment group. Animals in the treatment groups received 300 mg supplemental β-carotene daily for the test periods which varied from 6 to 8 weeks in length. To facilitate sample collections and observations, estrus was synchronized with two injections of 25 mg PGF 2α at 11 day intervals. The first injection was after 2 weeks of feeding supplemental β-carotene. Blood serum β-carotene concentrations were higher in the heifers fed supplemental β-carotene as compared to concentrations in control heifers after 1 week of feeding and this difference increased throughout the test periods. The interval from the second injection of PGF 2α to onset of estrus was shorter in the control heifers as compared to that interval in heifers supplemented with β-carotene (trial 1,44.0 vs 56.0 hr; trial 2, 51.3 vs 70.8 hr; trial 3, 40.7 vs 62.5 hr, respectively). The intervals from PGF 2α administration to the preovulatory LH peak (43.3 vs 61.5 hr) and ovulation (69.3 vs 85.9 hr) were also shorter in the control heifers in trial 3. No significant differences were found among treatments in the number of heifers that expressed estrus, the blood serum progesterone concentrations or the conception rates in any of the three trials.