Effects of zinc supplementation on growth performance, blood metabolites and lameness in young Holstein bulls

Abstract

One hundred and six young Holstein bulls (initial body weight = 376.7±18.3 kg) were randomly allocated in two treatments in a completely randomised design for 56 days. Dietary treatments consisted of (1) the basal diet (control; n=50); (2) basal diet plus 150 mg of Zn/kg of dry matter as ZnSO4 (n=56). Animals received a fresh total mixed ration at 09.00, 12.00 and 15.00 hours for ad libitum intake allowing 10% orts. Group dry matter intake was measured daily. On days 0, 28 and 56, body weights were recorded and blood samples were collected. Liver samples were taken on day 56. All claws of young bulls were examined every two weeks to identify claw lesions. Supplemental Zn decreased the average daily gain (ADG; p<0.01), gain:feed (G:F; p<0.001) and apparent DM digestibility (p<0.001); however, dry matter intake was not influenced. Plasma total protein (p<0.01), urea nitrogen (p<0.01) and albumin (p< 0.05) were higher in animals fed ZnSO4; however, serum cholesterol concentration decreased in Zn-supplemented animals. The prevalence of lameness (LN) was higher in control group than ZnSO4-supplemented treatment (28% vs. 12.5%; odds ratio or OR = 2.7; p<0.05). In summary, supplemental Zn decreased ADG and G:F, however, it could decrease the prevalence of LN. © 2012 Taylor and Francis.