EFFECT OF INJECTION OF BETA-CAROTENE OR VITAMIN-E AND SELENIUM ON FERTILITY OF LACTATING DAIRY-COWS

Experiments tested whether supplemental antioxidants improved fertilit y. To test effects of beta-carotene, cows in a hot environment were in jected with prostaglandin F-2 alpha (PGF(2 alpha)) and were given 3 in jections, im, of 800 mg beta-carotene or saline at Days -6 and -3 befo re the anticipated date of insemination and at insemination (n=37-41 i nseminated cows/group). There was no effect of beta-carotene on the pr oportion 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 intramus cular injections of vitamin E (500 mg) and selenium (50 mg) at 30 d po st partum (n=97) or were unheated controls (n=89). Treatment did not a ffect interval from calving to first insemination or the proportion of cows pregnant at first service, but it increased the pregnancy rate a t second service (69.8 vs 52.1%; P=0.07) and reduced services per conc eption(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 increas ed fertility in cattle that did not become pregnant at first service. (C) 1998 by Elsevier Science Inc.