Date of Graduation

5-2018

Document Type

Dissertation

Degree Name

Doctor of Philosophy in Animal Science (PhD)

Degree Level

Graduate

Department

Animal Science

Advisor/Mentor

Kegley, Elizabeth B.

Committee Member

Powell, Jeremy G.

Second Committee Member

Apple, Jason K.

Third Committee Member

Richeson, John

Fourth Committee Member

Thaxton, Yvonne V.

Keywords

Beef Calves; Castration; Growth-promoting Implants; Zinc

Abstract

In experiment 1, crossbred bull calves (n = 31; body weight (BW) = 114.3 ± 26.3 kg; age = 119 ± 18.4 d) were allocated to treatments by BW and birthdate. Twenty-seven bull calves were allocated to 3 injectable castration treatments (n = 9 calves/injectable castration treatment) to reflect 3 dosage levels of zinc. Intact bulls had greater (P < 0.001) serum testosterone concentrations compared to bulls injected with zinc. In experiment 2, crossbred beef bulls (n = 180) were blocked by initial BW (337 ± 10.9 kg; 6 blocks) and assigned randomly to 1 of 3 treatments on d 0: 1) INJ; received 1 mL (100 mg Zn) of a Zn solution in each testis, 2) BAN; banded, 3) BUL; intact. Final BW was greater (P < 0.01) for INJ (672 kg) and BUL (686 kg) compared to BAN (611 kg). Serum haptoglobin concentration was greater (P < 0.01) in INJ compared to BUL and BAN on d 1, 3, 5, and 7. Zinc injection resulted in sterilization but not castration in feedlot bulls although it was efficacious in castration of young bulls at branding. In experiment 3, crossbred beef steers (n = 106; BW = 96 ± 3.9 kg; age = 74 ± 2.0 d) were blocked by parity of dam (≤ 2 or > 2 parities), stratified by BW, calf age, calf sire, cow BW and body condition score to 1 of 4 treatments: 1) RALG, Ralgro, Ralgro, Revalor XS, at branding (D 0), weaning (D 156), and feedlot processing (D 325), 2) COMP, Component E-C, Component TE-G, Revalor XS, 3) N-REV, none, Revalor-G, Revalor XS, and 4) CTRL, no growth-promoting implants administered. Implantation of male calves at branding increased growth performance at weaning. At the end of the stocker phase on d 323, RAGL (330 kg), COMP (324 kg), and N-REV (318 kg) were heavier (P = 0.02) compared to CTRL (297 kg). Steers first implanted at weaning (N-REV) gained more during the stocker phase; however, steers implanted at branding had a 6 to 12 kg BW advantage at time of feedlot shipment.

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