Effects of Prenatal Androgenization, Melengestrol Acetate, and Synovex-H® on Feedlot Performance, Carcass, and Sensory Traits of Once-Calved Heifers

B. A. Reiling, L. L. Berger, Dan B Faulkner, F. K. McKeith, T. G. Nash, F. A. Ireland

Research output: Contribution to journalArticle

7 Citations (Scopus)

Abstract

Three studies were designed using a 2 × 2 factorial arrangement of treatments within each experiment to evaluate the effects of various management techniques on growth and carcass traits of once-calved heifers. In Exp. 1, 33 yearling (16 control [C] and 17 prenatally androgenized [PA]) and 39 once-calved (20 C and 19 PA) nonpregnant heifers were used to evaluate the effects of age and PA. Once-calved heifers were approximately 31 kg heavier (P < .03) on-test, initially consumed 11% more (P < .01) DM, and gained 11% faster (P < .08), but had similar (P = .44) gain to feed ratios (.138 vs. .131) as yearlings. Growth performance was not affected by PA. The yearling and once-calved heifers were then slaughtered at approximately 707 and 1,080 d of age, respectively. Despite maturity differences (P < .01), marbling scores (P = .26) and percentage of choice carcasses (P = .27) were similar. However, on the basis of newly accepted grading changes, percentage of once-calved heifer carcasses grading choice decreased from 57.3 to 34.4%. Organoleptic properties did not differ. Experiments 2 and 3 were then conducted to evaluate effects of commercially available products (melengestrol acetate [MGA] and Synovex-H®) on feedlot characteristics of heifers following weaning of their first calf. In Exp. 2, 48 once-calved Simmental-based heifers were fed during the summer to a constant compositional fat thickness of .8 cm. Experiment 3 was conducted in the late fall and early winter, during which 52 moderately sized heifers were fed for 116 d postweaning and slaughtered. Performance of heifers in Exp. 2 was not affected by MGA. However, heifers fed MGA in Exp. 3 gained 9% faster (P < .05) than controls. In Exp. 2, Synovex-H tended to improve ADG (P < .09) and feed efficiency (P < .07), but did not affect performance in Exp. 3. Most carcass traits were not affected by either treatment. Nonpregnant, once-calved heifers seem to have a large capacity for efficient weight gain as compared with yearling heifers. However, hormonal compounds, such as testosterone propionate provided pre- or postnatally (Synovex-H), and MGA do not appear to provide the consistent, positive responses often seen with younger, more typical feedlot heifers.

Original languageEnglish (US)
Pages (from-to)2043-2051
Number of pages9
JournalJournal of Animal Science
Volume74
Issue number9
StatePublished - Sep 1996
Externally publishedYes

Fingerprint

Melengestrol Acetate
melengestrol
masculinization
Virilism
feedlots
heifers
Testosterone Propionate
yearlings
Growth
Weaning
Weight Gain
Fats
carcass characteristics
testosterone propionate drug combination estradiol benzoate
Therapeutics
carcass grading
fat thickness
marbling
Simmental

Keywords

  • Androgens
  • Carcass
  • Estradiol
  • Heifers
  • Melengestrol
  • Performance

ASJC Scopus subject areas

  • Animal Science and Zoology

Cite this

Effects of Prenatal Androgenization, Melengestrol Acetate, and Synovex-H® on Feedlot Performance, Carcass, and Sensory Traits of Once-Calved Heifers. / Reiling, B. A.; Berger, L. L.; Faulkner, Dan B; McKeith, F. K.; Nash, T. G.; Ireland, F. A.

In: Journal of Animal Science, Vol. 74, No. 9, 09.1996, p. 2043-2051.

Research output: Contribution to journalArticle

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abstract = "Three studies were designed using a 2 × 2 factorial arrangement of treatments within each experiment to evaluate the effects of various management techniques on growth and carcass traits of once-calved heifers. In Exp. 1, 33 yearling (16 control [C] and 17 prenatally androgenized [PA]) and 39 once-calved (20 C and 19 PA) nonpregnant heifers were used to evaluate the effects of age and PA. Once-calved heifers were approximately 31 kg heavier (P < .03) on-test, initially consumed 11{\%} more (P < .01) DM, and gained 11{\%} faster (P < .08), but had similar (P = .44) gain to feed ratios (.138 vs. .131) as yearlings. Growth performance was not affected by PA. The yearling and once-calved heifers were then slaughtered at approximately 707 and 1,080 d of age, respectively. Despite maturity differences (P < .01), marbling scores (P = .26) and percentage of choice carcasses (P = .27) were similar. However, on the basis of newly accepted grading changes, percentage of once-calved heifer carcasses grading choice decreased from 57.3 to 34.4{\%}. Organoleptic properties did not differ. Experiments 2 and 3 were then conducted to evaluate effects of commercially available products (melengestrol acetate [MGA] and Synovex-H{\circledR}) on feedlot characteristics of heifers following weaning of their first calf. In Exp. 2, 48 once-calved Simmental-based heifers were fed during the summer to a constant compositional fat thickness of .8 cm. Experiment 3 was conducted in the late fall and early winter, during which 52 moderately sized heifers were fed for 116 d postweaning and slaughtered. Performance of heifers in Exp. 2 was not affected by MGA. However, heifers fed MGA in Exp. 3 gained 9{\%} faster (P < .05) than controls. In Exp. 2, Synovex-H tended to improve ADG (P < .09) and feed efficiency (P < .07), but did not affect performance in Exp. 3. Most carcass traits were not affected by either treatment. Nonpregnant, once-calved heifers seem to have a large capacity for efficient weight gain as compared with yearling heifers. However, hormonal compounds, such as testosterone propionate provided pre- or postnatally (Synovex-H), and MGA do not appear to provide the consistent, positive responses often seen with younger, more typical feedlot heifers.",
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