D.E. Franke

Comparison of feeding calves vs. yearlings

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Validation of commercial DNA tests for beef quality traits

Gene mapping and discovery programs have resulted in the detection of numerous DNA ‘markers’ for various beef cattle production traits. Prior to commercializing genetic markers, it is important to validate their purported effects on the traits of interest in different breeds and environments, and assess them for correlated responses in associated traits. One of the biggest challenges in achieving this objective is the availability of cattle populations with sufficient phenotypic data to assess the association between various traits and newly discovered genetic markers. Results from such validation studies to date have not been widely published and genetic marker tests sometimes may be commercialized prior to the collection of field validation data. In addition, conflicting reports about some commercially available markers, as well as the recognized occurrence of well-proven bulls with a high EPD for a given trait but carrying two copies of the “wrong” (unfavorable) marker for that trait, have made some producers wary of investing in DNA-based testing. Producers want to know whether DNA-based tests perform in accordance with the claims of the marketing company and are interested in third-party, independent validation of these tests. The objective of this study was to validate three commercially-available genetic tests (GeneSTAR Quality Grade, GeneSTAR Tenderness, and Igenity TenderGENE).

Genetic parameters for growth and carcass traits from crossbreeding

Growth and carcass data from 5 years of a long-term, rotational, crossbreeding project were used to calculate heritabilities and genetic and phenotypic correlations for direct and maternal birth and weaning weight, gain on feed, hot carcass weight, ribeye area, marbling score, and age at slaughter. Angus, Brahman, Hereford, Charolais, Simmental, and Gelbvieh breeds were involved. Heritabilities of traits ranged from low (maternal weaning weight 0.04) to moderate (direct weaning weight 0.41). Direct birth weight, direct weaning weight, gain on feed, and hot carcass weight had moderate to high genetic correlations. Marbling had negative genetic correlations with birth and weaning weight but positive correlations with slaughter age and hot carcass weight.

Effects of postweaning management system and breed on growth and carcass traits

Data from 5 years of a long-term, rotational, crossbreeding project were used to calculate heritabilities and correlations and to make breed comparisons for growth rate and carcass traits in two different postweaning management systems. The traits studied were weight per day of age, hot carcass weight, ribeye area, marbling score, and days of age at slaughter. One group was placed on full feed after weaning. A second group underwent a backgrounding phase for 7 months at Louisiana State University before being placed on feed at KSU. The breeds involved were Angus, Brahman, Charolais, Hereford, Simmental, and Gelbvieh. Differences in heritabilities between management systems were generally small, indicating similar genetic expression across management systems. Genetic correlations also were high except for marbling score, which indicates some difference in genetic expression between management systems for this trait. Some changes in rank of breeds occurred between management systems, but they generally were not significant.

Comparisons among crossbred beef cattle for growth and carcass traits

Data from 5 years of a long-term, rotational crossbreeding project were used to compare breeds for growth and carcass traits. The traits of interest were direct and maternal birth and weaning weights, gain on feed, hot carcass weight, ribeye area, marbling score, and slaughter age. Angus, Brahman, Hereford, Charolais, Simmental, and Gelbvieh breeds were involved. Simmental and Gelbvieh were used as terminal breeds, so maternal effects were not calculated for them. Brahman breeding caused an increased direct birth weight of the calves, but the maternal influence of Brahman decreased birth weight. No difference occurred in maternal weaning weight among the Angus, Brahman, Charolais, and Hereford breeds. Charolais and Simmental breeding increased gain on feed. Charolais, Simmental, and Gelbvieh breeding resulted in the heaviest hot carcass weights and largest ribeye areas. Simmental, Charolais and Angus breeding resulted in the most marbling. Hereford and Angus breeding reduced age at slaughter compared to the other breeds. All six breeds have some advantages in the traits studied. Which breed will work best depends on the production environment and goals of the producer.

Breed and management comparisons and genetic parameters for carcass traits

Carcass data from 5 years of a long-term, rotational , crossbreeding project were used to calculat e heritabilities, genetic and phenotypic correlations , and management effects and to compare breeds for marbling, ribeye area, and hot carcass weight. Angus, Brahman, Charolais, Hereford, Pol led Hereford, Gelbvieh, and Simmental breeds were involved. Sixty percent of the steer calves were fed as calves and 40% as yearlings. Heritabilities were .40 for marbling, .46 for ribeye area, and .51 for carcass weight. Genetic and phenotypic correlations were high between carcass weight and ribeye area but low between marbling and the other traits. St eers fed as calves had more marbling and lighter carcasses than steers fed as yearlings. Higher percentages of Gelbvieh or Brahma n breeding resulted in lower (P<.05) marbling . Increased percentage of Charolais and Simmental breeding increased (P<.05) ribeye area and tended to increase carcass weight without reducing marbling

The relationships of color to performanceand carcass traits in cattle

The effects of primary color (black, red, or white) on performance and carcass characteristics of 253 cross-bred calves were evaluated. The only effect of color was that white calves had lighter birth weights than red calves, which was probably the result of the maternal influence of the Brahman breed. White calves also had a lower carcass yield grade than red calves. No other effects of color on performance or carcass traits were found. It can be concluded that knowledge of breed and expected progeny differences (EPD) of the sire within the breed are more accurate methods of predicting the future performance and carcass characteristics of calves than color.

Comparison of feedlot and carcass characteristics of Angus, Hereford, Brahman, Charolais, and Gelbvieh crossbred steers

Feedlot performance of 207 steers with various percentages of Angus, Hereford, Charolais, Brahman, and Gelbvieh breeding were compared at a constant 1) days fed, 2) adjusted carcass backfat, and 3) slaughter weight. As the percentage of Angus, Hereford, or Brahman increased, growth rate decreased, whereas increasing the percentage of Charolais increased growth rate. Increasing the percentage of Gelbvieh increased weaning weight but had little effect on post-weaning gains. Increasing percentage of Charolais increased feed conversion efficiency, whereas the other breeds were similar, except that at a constant slaughter weight, greater percentage of Hereford improved feed conversion efficiency.

Breed and management system effects onfeedlot performance and carcass traits

Eighty nine steers with different proportions of Angus, Hereford, Charolais, Brahman, and Gelbvieh breeding from rotational and terminal crossbreeding systems were produced in Louisiana and finished at KSU. Half of each breed group was placed in the feedlot at weaning (calves) and the other half as yearlings. Half of the each group was slaughtered at a low (0.3-0.4 in.), and the other half at high (0.5 0.6 in.) fat thickness. As percentage of Charolais and Gelbvieh breeding increased, feedlot performance improved. As percentage of Charolais, Gelbvieh, and Angus increased, carcass desirability improved. Steers started on feed at weaning were more efficient in feed conversion and were more profitable than those started as yearlings. Age did not affect carcass marbling or quality grade.