Effects of pre- and postnatal testosterone treatments on growth and carcass traits of heifers used in a single-calf heifer system

Three studies evaluated growth and carcass traits of heifers in a single-calf heifer system. In Study 1, 24 prenatally androgenized (PA) heifers and 27 control (C) heifers were fed a finishing diet postpartum and slaughtered at 1.1 cm s.c. fat. Calves were weaned at 117 d of age. Preweaning, PA heifers gained 22.5% faster $(P<.01)$ and were 17.3% more efficient $(P<.01)$ than C heifers. Calf gain was not affected. The PA and C pairs gained 2.88 and 2.53 kg/d, respectively, and efficiency improved $(P<.01)$ 10.8%. Pre- and postweaning, PA heifers gained 23% faster $(P<.01)$ and were 16% more efficient $(P<.02)$ than C heifers. At slaughter, PA and C heifers averaged 853 and 865 d of age, respectively. Skeletal (B$\sp0)$ and lean (A$\sp{60})$ maturity scores were similar between treatments. One carcass was C-maturity. Marbling scores exceeded Small$\sp{50},$ and sensory traits were similar. In Exp. 1 of Study 2, 33 yearling (16 C and 17 PA) and 39 once-calved (20 C and 19 PA) heifers were used to evaluate effects of age and PA. Once-calved heifers gained 11% faster $(P<.08),$ but had similar $(P=.44)$ gain to feed ratios (.138 vs..131) as yearlings. Growth was not affected by PA. Yearling and once-calved heifers averaged 707 and 1080 d of age, respectively, at slaughter. Despite maturity differences $(P<.01),$ marbling scores $(P=.26)$ and percentage of choice carcasses $(P = .27)$ were similar. Organoleptic properties did not differ. Experiments 2 and 3 evaluated the effect of melengestrol acetate (MGA) and Synovex-H on feedlot traits of once-calved heifers. In Exp. 2, 48 once-calved Simmental cross heifers were fed to possess.8 cm s.c. fat. In Exp. 3, 52 moderately sized heifers were fed for 116 d. Performance in Exp. 2 was not affected by MGA, but heifers fed MGA in Exp. 3 gained 9% faster $(P<.05)$ than C heifers. In Exp. 2, Synovex-H improved ADG $(P<.09)$ and feed efficiency $(P<.07),$ but did not affect performance in Exp. 3. Carcass traits were not affected. In Study 3, 12 C and 12 PA L and five (2 C and 3 PA) nonlactating (NL) heifers were used to assess effects of PA and L on metabolic activity of s.c. adipose tissue (AT). The NL heifers gained.22 kg/d (13.9%) faster $(P=.20)$ than L heifers and had greater fat deposition, and PA heifers were fatter but gained 14.6% faster than C heifers, preweaning. Calves were weaned at 112 $\pm$ 1 d of age, and AT was biopsied at 77 and 126 d postpartum. Epinephrine (E) and norepinephrine (NE) increased in vitro fatty acid (IVFA) release 25 $(P<.01)$ and 15% $(P<.06),$ respectively. Near-maximal lipolytic release of IVFA as estimated by E with theophylline and adenosine deaminase (ETAD) stimulation was 73% greater $(P<.01)$ than basal rates. Basal IVFA release was not affected by PA, but ETAD-stimulated rates decreased $(P<.04).$ Basal, E-$(P=.22),$ and NE-stimulated $(P=.31)$ IVFA release rates were similar between C and PA. (Abstract shortened by UMI.)

Name thesis:degree_name

Ph.D.

Level thesis:degree_level

Dissertation

Discipline thesis:degree_discipline

Animal Sciences

Grantor

University of Illinois at Urbana-Champaign

Year dc:date

2011

Author dc:creator

• Reiling, Bryan Alan

Contributors dc:contributor

• Berger, Larry L.

• Biology, Animal Physiology
• Agriculture, Animal Culture and Nutrition

Statement dc:rights

• Copyright 1996 Reiling, Bryan Alan

Language dc:language

eng

Identifier

9780591088359
AAI9702650
(UMI)AAI9702650

OAI identifier oai:identifier

oai:www.ideals.illinois.edu:2142/19981