The Effects of a Zinc-Methionine Supplementation in High Producing Dairy Cows

and Implications The objective of this study was to examine the effects of a Zn-methionine complex in diet on milk yield, milk component yields, SCC, and milk Zn concentration of Holstein cows around peak lactation. After matching for parity and days in milk (DIM), 12 lactating Holstein cows (67 ± 2.5 DIM; 1385 ± 43 kg BW) were assigned to one of two dietary treatments: 1) control (CTL, n = 6), a TMR diet with 74 mg/kg added Zn in the form of zinc sulfate, n = 6) or 2) CTL supplemented with Zn-methionine complex (Zn-Met, n = 6) providing additional 20 mg of Zn/kg (512 mg/head/d). Dry matter intake (DMI) was lower by 0.8 kg/d for Zn-Met than CTL throughout the study (P = 0.05). Milk yield of Zn-Met decreased compared to CTL (40 vs 42 kg/d, P = 0.01) during the first 35 d but had similar milk yield during the last 35 d of the study. Milk protein and fat percentages, and fat yield were not different between treatments. Milk protein yield was similar between treatments during the first 35 d but tended to increase for Zn-Met (1.41 vs. 1.33 kg/d, P = 0.10) during rest of the study. Cows receiving Zn-methionine complex tended to have lower SCC (126 vs 328 ×103 cells/mL, P = 0.07) and greater concentration of Zn (4.48 vs 4.06 ppm, P = 0.05) in milk throughout the study. Overall, the present Znmethionine complex tended to improve milk protein yield and SCC more prominently as feeding progressed. However, it decreased DMI suggesting a negative impact on palatability of the diet.