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2010-Allais_et_al - The two mutations Q204X and nt821 of...

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Denoyelle, C. Bernard-Capel, L. Journaux, A. Bonnot and G. Renand S. Allais, H. Levéziel, N. Payet-Duprat, J. F. Hocquette, J. Lepetit, S. Rousset, C. quality in young heterozygous bulls of French beef breeds The two mutations, Q204X and nt821, of the myostatin gene affect carcass and meat 2009-12-04T11:46:18-08:00; 2010, 88:446-454.doi: 10.2527/jas.2009-2385 originally published online J ANIM SCI http://jas.fass.org/content/88/2/446 the World Wide Web at: The online version of this article, along with updated information and services, is located on www.asas.org by guest on May 21, 2011 jas.fass.org Downloaded from
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ABSTRACT: The availability of genetic tests to de- tect different mutations in the myostatin gene allows the identification of heterozygous animals and would warrant the superiority of these animals for slaughter performance if this superiority is confirmed. Thus, 2 mutations of this gene, Q204X and nt821, were studied in 3 French beef breeds in the program Qualvigène. This work was done with 1,114 Charolais, 1,254 Lim- ousin, and 981 Blonde d’Aquitaine young bulls from, respectively, 48, 36, and 30 sires and slaughtered from 2004 to 2006. In addition to the usual carcass traits recorded at slaughter (e.g., carcass yield, muscle score), carcass composition was estimated by weighing internal fat and dissecting the 6th rib. The muscle characteristic traits analyzed were lipid and collagen contents, muscle fiber section area, and pH. Regarding meat quality, sensory qualities of meat samples were evaluated by a taste panel, and Warner-Bratzler shear force was mea- sured. Deoxyribonucleic acid was extracted from the blood samples of all calves, the blood samples of 78% of the dams, and the blood or semen samples of all the sires. Genotypes were determined for 2 disruptive mutations, Q204X and nt821. Analyses were conducted by breed. The superiority of carcass traits of calves car- rying one copy of the mutated allele (Q204X or nt821) over noncarrier animals was approximately +1 SD in the Charolais and Limousin breeds but was not signifi- cant in the Blonde d’Aquitaine. In the Charolais breed, for which the frequency was the greatest (7%), young bulls carrying the Q204X mutation presented a carcass with less fat, less intramuscular fat and collagen con- tents, and a clearer and more tender meat than those of homozygous-normal cattle. The meat of these animals also had slightly less flavor. Also in the Charolais breed, 13 of 48 sires were heterozygous. For each sire, the sub- stitution effect of the wild allele by the mutant allele was approximately +1 SD for carcass conformation and yield, showing that the estimate of the substitution ef- fect was independent of family structure, as it ought to be for a causal mutation. These results illustrate the challenge of using genetic tests to detect animals with the genetic potential for greater grades of carcasses and meat quality.
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