Influence of organic zinc on lactation performance and somatic cell count in dairy cows

The objective of the study was to evaluate the effect of organically chelated zinc methionine (Zn-Met) supplementation on lactation performance of dairy cattle, i.e. milk yield (MY), milk components, and the somatic cell count (SCC) in early lactation. Eighty multiparous cows received two treatments (n = 40 per group) from 21 days prepartum throughout 14 weeks post partum (p.p.). Treatments consisted of 1) supplemental Zn-Met at the dose of 30 mg Zn/kg dry matter (DM) of the total mixed ration (TMR) for the supplemented (S) group; and 2) basal TMR without supplementation for the control (C) group. Daily MY of Zn supplemented cows 30 days p.p. was in not significantly affected (P > 0.05) by the treatment. After 60 days, the MY of the S-group was significantly higher (S: 44.70 +/- 4.24 kg vs. C: 42.08 +/- 4.60 kg, respectively); (P < 0.05). Ninety days p.p. there was a highly significant difference ( P < 0.005) as well (S: 43.22 +/- 4.47 kg vs. C: 39.98 +/- 4.80 kg). Supplemented cows also produced significantly more milk fat and milk protein than the control on days 60 and 90 of the trial. There was a significant drop and a decreasing trend during the entire trial in SCC in S-group. Milk quality and udder health were positively affected by the Zn-Met treatment. This finding has an important implication for veterinary practice in an era of antibiotic reduction.