EFFECT OF DIETARY ZINC-OXIDE ON THE PLASMA CAROTENOID CONCENTRATION OF STEERS

The effect of supplementary zinc oxide (ZnO), administered at differen t doses and frequencies, on plasma carotenoid (PC) concentrations of b eef cattle was determined in three experiments. In Experiments 1 and 2 , Angus and Angus crossbred steers were drenched twice weekly with the equivalent of 12.5 and 25 g ZnO/100 kg liveweight per week (Experimen t 1), and 50 g ZnO/100 kg liveweight per week (Experiment 2) for 31 an d 25 days respectively. In Experiment 3, Angus x Friesian steers recei ved a daily supplement of 1 kg pellets containing 10 g ZnO per head fo r 28 days. There was no effect of drenching with ZnO on PC concentrati ons but by day 28, the daily supplement of 10 g ZnO increased PC conce ntration by 22%. The results indicate that ZnO supplements can not be used to reduce carotenoid absorption in cattle.