Effect of organic trace minerals supplementation during early postpartum on milk composition, and metabolic and hormonal profiles in grazing dairy heifers

Abstract

The effect of complexed trace minerals supplementation on productive, reproductive and metabolic variables during early postpartum of grazing primiparous dairy cows =) was investigated. Pasture-fed Holstein heifers were offered (supplemented group; SG, n=60) or not (control group; CG, n=60) a commercial trace mineral supplement during the first 90 days of lactation. Milk production and composition were determined monthly. Reproductive function was evaluated by calving-first service interval, number of services per conception, and pregnancy rates. Non-esterified fatty acids, β-hydroxybutyrate, insulin, and insulin-like growth factor-1 were determined on blood samples collected on days postpartum -7 ± 4, 30 and 60. Supplementation did not affect milk production or its composition, except for fat percentage that tended to be higher in SG than CG. Calving-first service and calving-conception intervals were shorter in SG than CG but number of services per conception and pregnancy rates did not differ between treatments. No lameness was observed during the period evaluated and although a beneficial effect of SG was found in locomotion score, it was not clinically relevant (scores 1-2). Metabolites and hormones concentrations did not differ between treatments. Organic trace mineral supplementation had a transient beneficial effect on milk composition on the intervals from calving to first service and from calving to conception, with no changes in metabolic and endocrine profiles during the transition period primiparous dairy cows on grazing conditions.