Effect of zinc from zinc sulfate on trace mineral concentrations of milk in Varamini ewes

This study was conducted to evaluate the effect of feeding supplemental zinc (zinc sulfate) in different levels (15, 30, or 45 mg/kg) on trace mineral concentrations in milk of ewes. Thirty lactating Varaminni ewes were assigned to three experimental groups according to their live body weights, milk production and lambs sex in a completely randomized design. Ewes were fed a basal diet containing alfalfa, wheat straw, cottonseed meal, barley grain, wheat bran, cracked corn and vitamin-mineral supplements at 3.2% of body weight (BW) to meet NRC requirements for protein, energy and macro minerals. The basal diet contained 15 mg/kg Zn and zinc sulfate was added to the basal diet to supply 30 or 45 mg/kg of dietary zinc. Daily milk yielded was recorded at 7 days intervals and samples of the milk were taken once per week for determination of milk composition and trace mineral concentration. Concentrations of Zn, Cu, Mn and Fe in milk were determined. Dry matter intake (DMI), milk yield and milk compositions were not affected by supplemental zinc (P > 0.05). But zinc concentrations in milk were affected by supplemental zinc (P 0.05). It suggests that supplementation of ewes diet with zinc sulfate could be an effective way to increase zinc concentration in milk when zinc concentration of basal diets is limited for ewes in lactation period.