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

Authors: STEWART, WHIT - University Of Wyoming; Murphy, Thomas - Tom; PAGE, CHAD - University Of Wyoming; RULE, DAN - University Of Wyoming; Taylor, Joshua - Bret; AUSTIN, KATHLEEN - University Of Wyoming; PANKEY, CHRIS - West Virginia School Of Osteopathic Medicine

Submitted to: Applied Animal Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 9/2/2020
Publication Date: 12/2/2020
Publication URL: https://handle.nal.usda.gov/10113/7198243
Citation: Stewart, W.C., Murphy Jr, T.W., Page, C.M., Rule, D.C., Taylor, J.B., Austin, K., Pankey, C. 2020. Effect of increasing dietary zinc sulfate fed to primiparous ewes: I. Effects on serum metabolites, mineral transfer efficiency, and animal performance. Applied Animal Science. 36(6):839-850. https://doi.org/10.15232/aas.2020-02057.
DOI: https://doi.org/10.15232/aas.2020-02057

Interpretive Summary: Intermountain West sheep production systems make up approximately 35% of the breeding sheep inventory in the U.S. and most of these animals rely upon rangelands with senesced forages as a major proportion of their diet during the critical production periods of breeding and gestation. Zinc is a trace mineral that is essential to sheep health and performance but its content in forages is variable throughout the year and generally below required thresholds in dormant rangelands. Therefore, zinc and other minerals should be provided as a supplement to the basal diet during these timepoints. However, estimations used to calculate zinc requirements require accurate production assumptions (e.g., body weight, prolificacy, wool growth, etc.) and may be different among breeds or may not account for continual phenotypic changes due to selection. The objectives of this research were to determine the effects of increasing zinc concentrations supplemented in late gestation on ewe and lamb serum metabolites, serum mineral element concentrations and transfer efficiency ratios, and ewe and lamb performance. Commercial Rambouillet and Hampshire ewes were fed 1 of 3 zinc supplements from mid-gestation to parturition: at current recommendation (Control), ~4 times Control, and ~7 times Control. Treatment group had little effect on ewe and lamb performance or health, however, important breed differences were observed. Rambouillet and Hampshire ewes had similar serum zinc concentrations but Rambouillet lambs born to Rambouillet ewes had 25% greater serum zinc at birth than Hampshire lambs born to Hampshire ewes. Therefore, the ability of Rambouillet ewes to transfer zinc to their lambs was approximately twice as great as Hampshire ewes. Results suggest feeding zinc beyond current recommendations from mid-gestation until parturition had minimal beneficial effects on fine-wool or meat-type ewes and lambs. Breed differences observed in maternal transfer of zinc may provide insights into adaptive trace mineral supplementation strategies based on breed type and related levels of production.

Technical Abstract: The objectives of this research were 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 × NRC), Zn500 (n = 19, 500 mg/kg Zn, ˜ 4 × NRC), and Zn1000 (n = 15, 1000 mg/kg Zn, ˜ 7 × NRC). Treatments were administered in pelleted alfalfa (0.45 kg/ewe/d) fortified with increasing Zn concentrations fed from 87.5 ± 8.9 days 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 grease fleece weight (GFW) the following year was greater for Zn500 than Zn1000 ewes (4.13 ± 0.18 kg vs. 3.48 ± 0.19; P = 0.03) but did not differ between CON and the other treatments (3.68 ± 0.22; 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 than 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 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 ß-hydroxybutyrate (BHB) and cortisol (4.44 mg/dL and 31.9 ± 3.89 ng/mL, respectively) concentrations compared to 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). Results suggest feeding Zn beyond current NRC recommendations from d 87 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 to the neonatal lamb may provide insights into adaptive trace mineral supplementation strategies based on breed type and related levels of production.