Biomedical subjects

G H Rouse

Publications and source records attributed to G H Rouse.

3 recordsLinked to original sources

PubMed1993

Genetic parameters for carcass traits estimated from Angus field records.

The American Angus Association has sponsored a carcass evaluation since 1974. The carcass data collected as a part of this program are used by the association to conduct a biannual sire evaluation for carcass merit. This paper presents age-adjustment factors and genetic parameter estimates for carcass traits to be used in the Angus carcass genetic evaluation program. Because of the large range in slaughter ages, age classes were defined as all those animals slaughtered at an age of < or = 480 d and those with a slaughter age > 480 d. Linear and quadratic partial regressions on slaughter age for hot carcass weight (HCW), USDA marbling score (MS), 12th rib longissimus muscle area (LMA), and 12th-rib fat thickness (FT) were estimated within sex and age class. Quadratic age regressions were not significant, nor was the linear age regression coefficient for FT in steers in the > 480-d age class. Heritability estimates for age-constant HCW, MS, LMA, and FT were .31, .26, .32, and .26, respectively. The estimated genetic correlation (rg) between HCW and LMA was .47. The estimated rg between HCW and FT was .38 and between MS and FT was -.13. The linear genetic trends for CWT and LMA were significantly positive at .414 kg/yr and .075 cm2/yr, respectively. The genetic trends for FT and MS were very small but significantly negative at -.004 cm/yr and -.003 units/yr, respectively.

Adipose Tissue↗

PubMed1992

Predicting percentage of retail yield from carcass measurements, the yield grading equation, and closely trimmed, boxed beef weights.

Over the past 3 yr, 100 carcasses (64 steers, 24 bulls, and 12 heifers) were fabricated into closely trimmed (6 mm maximum fat cover), boxed beef and further evaluated for percentage of retail yield at the Iowa State University Meat Laboratory. Hot carcass weight ranged from 235 to 399 kg with a least squares mean (LSM) and standard error across all sex classes of 318 +/- 3 kg. Additionally, fat cover ranged from .30 to 1.78 cm with an average of .91 +/- .05 cm. The LSM for longissimus muscle area (LMA) across all sex classes was 81.6 +/- 1.0 cm2. Bulls had significantly less subcutaneous fat (P less than .01) and greater LMA (P less than .01) than did either steers or heifers. Retail yield from the boxed chuck, expressed as a percentage of cold carcass weight, was 19.2 for bulls and 14.8 for steers. This difference was due primarily to a reduction of intermuscular fat. Similarly, bulls had a greater yield (P less than .01) of the boxed round than did steers. When cattle of differing frame sizes were compared, only percentage of retail yield of the boxed round was significant (P less than .01): large-framed cattle yielded 14.3 +/- .2%, compared with 12.8 +/- .2% for the small-framed cattle. When all possible regression analyses were run, sex class differences accounted for 25.7% of the variation in retail yield. The current USDA retail yield equation accounted for only 37.2% of the variation. Percentage of closely trimmed, boneless round had an R2-value of .57.(ABSTRACT TRUNCATED AT 250 WORDS)

Abattoirs↗

PubMed1988

Optimal beef cattle diets formulated by nonlinear programming.

A beef diet model based on National Research Council recommendations is significantly nonlinear for feed ingredients, daily gain and weight of cattle. Solving a diet model has been difficult, but advances in nonlinear programming now allow solutions that are quick and easy. This study developed a nonlinear programming method for optimally planning a feeding program by choosing feeds, daily gains and selling weight. Two types of diets are important for this purpose:optimal-return diets and least-cost-gain diets. For a given weight of cattle, an optimal-return diet chooses feeds and daily gain to maximize returns above feed costs. A least-cost-gain diet chooses feeds and daily gain to minimize feed plus yardage costs per kilogram of gain. In an optimal feeding program, a sequence of optimal-return diets is fed to increasing weights of cattle. Feed costs plus yardage per kilogram of gain rise to equal the actual selling price at the optimal selling weight, and the cattle are sold. Cattle feeders and researchers with access to a microcomputer can maximize net returns from a feeding program.

Animal Husbandry↗