Effect of injection of β-carotene or vitamin E and selenium on fertility of lactating dairy cows

Experiments tested whether supplemental antioxidants improved fertility. To test effects of beta-carotene, cows in a hot environment were injected with prostaglandin F-2 alpha (PGF(2 alpha)) and were given 3 injections, im, of 800 mg beta-carotene or saline at Days -6 and -3 before the anticipated date of insemination and at insemination (n=37-41 inseminated cows/group). There was no effect of beta-carotene on the proportion of cows detected in estrus following PGF(2 alpha), timing of estrus after PGF(2 alpha), injection or pregnancy rate in inseminated cows. In a second trial, cows in a temperate climate received intramuscular injections of vitamin E (500 mg) and selenium (50 mg) at 30 d post partum (n=97) or were unheated controls (n=89). Treatment did not affect interval from calving to first insemination or the proportion of cows pregnant at first service, but it increased the pregnancy rate at second service (69.8 vs 52.1%; P=0.07) and reduced services per conception(1.7 vs 2.0; P<0.05) and interval from calving to conception (84.6 vs 98.1; P<0.05). Thus, injection of vitamin E and selenium increased fertility in cattle that did not become pregnant at first service. (C) 1998 by Elsevier Science Inc.