Date of Graduation

5-2026

Document Type

Thesis

Degree Name

Bachelor of Science in Agriculture

Degree Level

Undergraduate

Department

Animal Science

Advisor/Mentor

Elizabeth Kegley

Committee Member

Jeremy G Powell

Second Committee Member

Ken Coffey

Abstract

The objective of this study was to determine the effect of increasing zinc supplementation from organic-complexed sources to beef cows during gestation on calf performance. In May 2025, during gestation, Angus crossbred cows were confirmed pregnant with female sexed semen (n = 83) and enrolled in the current study. Cows (4.7 ± 2 years of age and 531 ± 84.4 kg body weight, mean ± standard deviation) were allotted to 4 groups (20 to 21 cows/group) based on, sire of heifer calf, cow age, and cow body weights taken at weaning. Assigned groups received 1 of 2 treatments (2 groups/treatment): 1) a grain supplement with inorganic zinc (Zn) to meet current National Academics of Sciences, Engineering, and Medicine (NASEM) requirements (CONTROL), and 2) a grain supplement containing an additional 360 mg/d of Zn as an amino acid complex (Zinpro Availa Zn) (HIGHZN). The supplements were offered (1.36 kg/cow offered 3 days/week) from day 162 of gestation until the average calf was 30 days old. Cows grazed mixed grass pastures and were offered free-choice white salt and water for ad libitum intake. Before calving, a subset of cows (n = 32; 16 cows/treatment) were transferred to a closer working facility for intensive sampling procedures. Cows were provided with 2.43-ha grass paddocks where routine calf checks occurred. Once a cow had given birth, the cow-calf pair was left alone until the calf stood and suckled once, then were moved to a working barn for sample collection from the dam. While restrained in the chute, blood samples were collected from the cow via jugular venipuncture, and colostrum samples were collected from each quarter and composited for each cow. Birth weights and morphometric measurements were recorded for each calf. At 48 hours following parturition, the calves were restrained, and blood samples were collected. Calf whole blood samples were utilized for a complete blood cell (CBC) analysis. Colostrum and serum samples were further analyzed for immunoglobulin A and G concentrations. All data were analyzed using MIXED and GLIMMIX procedures of SAS 9.4 with sire and location as random effects and group being the subject. Maternal dietary treatments had no effect on birth weights (P = 0.28; CONTROL = 29 kg vs. HIGHZN = 30 kg). The number of cows that remained open (n = 6 vs. 2) and the number of calves that died (n = 5 vs. 3) were not affected by treatment but were numerically greater for CONTROL cows (P ≥ 0.22). Calf morphometric measurements recorded at birth were not different between maternal treatments (P ≥ 0.16). The number of basophils tended to be greater (P = 0.09) for the calves residing on the HIGHZN treatment (0.17 K/µL) when compared to calves on the CONTROL (0.09 K/µL) treatment. To conclude, organic-complexed Zn supplementation during gestation had minimal effects on the calves at birth; however, further investigation on later developmental differences in heifer calves is warranted.

Keywords

Zinc; beef cattle; gestation; supplement

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