289 Effects of dietary Zn on ewe milk minerals and somatic cell count

Abstract

Abstract The objectives of the current study were to evaluate the effects of dietary Zn fed at approximately 3 times NRC recommendations on milk Zn concentrations and mammary health. Within Rambouillet (WF) and Hampshire (BF) breeds, ewes were ranked by BW and randomly assigned down the rank into 2 treatment groups: Control (n = 45, 37 mg Zn/kg DM) and Zn treatment (n = 44, 113 mg Zn/kg DM). Treatments were delivered via a ZnSO4-fortified alfalfa pellet fed at a rate of 0.45 kg/d DM from a RFID-activated automated feeder from approximately 6 wk before to 4 wk after lambing. Ewe milk was collected twice weekly, and analyzed for mineral content (d 0, 10, and 30 of lactation) and somatic cell count (SCC; d 3–5, 6–9, 10–12, 13–16, 17–19, 20–23, 24–26, 27–29, or 30–32). Single-bearing ewes had greater Ca, Mg, and P (P ≤ 0.04) than multiple-bearing ewes. Day of lactation influenced milk Mg, P, and Zn (P < 0.01), and values generally decreased as lactation progressed. Milk Zn was 1.7-fold greater (P < 0.01) for Zn treatment than Control ewes. Milk Ca, Mg, and P were greater for Control than Zn treatment (P ≤ 0.02) ewes. A breed × litter size effect was detected for LogSCC (P = 0.02). Single-bearing WF ewes had lower LogSCC than multiple-bearing WF ewes (5.36 ± 0.09 vs 5.74 ± 0.07; P < 0.01) but litter size did not affect BF ewe LogSCC (5.80 ± 0.08 vs 5.79 ± 0.09; P = 0.92). Day of lactation impacted ewe SCC (P < 0.01), with peak SCC between d 6 and 9, which began to decline as lactation progressed. In conclusion, dietary Zn above NRC recommendations increased milk Zn.