Effects of increasing dietary zinc sulfate fed to primiparous ewes: I. Effects on serum metabolites, mineral transfer efficiency, and animal performance

The objective of this research was to determine the effects of increasing Zn concentrations during late gestation on serum metabolites, serum mineral element transfer efficiency ratios (TE), and ewe and lamb performance in a semi-extensive management system. Commercial white-face (WF; n = 23) and black-face (BF; n = 24) ewes (age ≈18 mo; BW 87.48±8.37 kg) were sorted into breed-type groups and within groups ranked by BW and randomly divided into 3 dietary supplement treatment groups along the rank: CON (n = 13, 40 mg/kg Zn, ≈1 × NASEM recommendations), Zn500 (n = 19, 500 mg/kg Zn, ≈4 × NASEM recommendations), and Zn1000 (n = 15, 1,000 mg/kg Zn, ≈7 × NASEM recommendations). Treatments were administered in pelleted alfalfa (0.45 kg/ewe per day) fortified with Zn sulfate to increase Zn concentrations fed from 87.5±8.9 d of gestation until parturition. Maternal treatment did not affect ewe BW change throughout the experiment, nor serum metabolites, mineral element TE, or progeny performance through weaning (P ≥ 0.06). However, ewe greasy fleece weight the following year was greater for Zn500 than Zn1000 ewes (4.13±0.18 kg vs. 3.48±0.19 kg; P = 0.03) but did not differ between CON and the other treatments (3.68±0.22 kg; P ≥ 0.22). The most marked effects were observed between breeds where Zn TE of WF ewes and lambs (264.3 ± 23.2) was approximately twice that of BF ewes and their lambs (165.4 ± 19.7; P < 0.01). Serum Fe was greater in WF ewes and lambs (2.24±0.10 and 1.34±0.09 μg/mL, respectively) than in BF ewes and their lambs (1.82±0.09 and 1.05±0.09 μg/mL, respectively; P < 0.01). At birth, WF lambs had greater serum BHB and cortisol (4.44 mg/dL and 31.9±3.89 ng/mL, respectively) concentrations compared with BF lambs (3.97 mg/dL and 22.0±3.62 ng/mL, respectively; P < 0.03) and also exhibited 6.8% greater vigor (P = 0.02). The results suggest feeding Zn supplemented from Zn sulfate beyond current NASEM recommendations from d 87 of gestation until parturition had minimal beneficial effects on fine-wool or meat-type ewes and lambs. Breed differences observed in serum mineral element concentrations (Fe and Zn) and related TE of the neonatal lamb may provide insights into adaptive trace mineral supplementation strategies based on breed type and related levels of production.