Journal of Animal Science

Search for quantitative trait loci affecting growth and carcass traits in a cross population of beef and dairy cattle

B. GutiƩrrez-Gil *, J. L. Williams **, D. Homer ***, D. Burton*, C. S. Haley*, and P. Wiener*

Abstarc :

A genome scan to detect QTL influencing growth and carcass-relatedtraits was conducted in a Charolais x Holstein crossbred cattlepopulation. Phenotypic measurements related to growth and carcasstraits were made on the 235 second-generation crossbred malesof this herd (F2 and reciprocal backcrosses), which were bornin 4 consecutive annual cohorts. Traits measured in vivo wererelated to birth dimensions, growth rates, and ultrasound measurementsof fat and muscle depth. The animals were slaughtered near atarget BW of 550 kg, and a wide range of postmortem traits weremeasured: visual assessment of carcass conformation and carcassfatness, estimated subcutaneous fat percentage, weights of kidneyknob and channel fat, and weights of carcass components aftercommercial and full-tissue dissections. The whole population,including grandparents, parents, and the crossbred bulls, wasgenotyped initially for 139 genome-wide microsatellite markers.Twenty-six additional markers were subsequently analyzed toincrease marker density on some of the chromosomes where QTLhad been initially identified. The linear regression analysesbased on the 165 markers revealed a total of 51 significantQTL at the suggestive level, 21 of which were highly significant(F-value >= 9; based on the genome-wide thresholds obtained inthe initial scan). A large proportion of the highly significantassociations were found on chromosomes 5 and 6. The most highlysignificant QTL was localized between markers DIK1054 and DIK082on chromosome 6 and explained about 20% of the phenotypic variancefor the total bone proportion estimated after the commercialdissection. In the adjacent marker interval on this chromosome,2 other highly significant QTL were found that explain about30% of the phenotypic variance for birth dimension traits (BWand body length at birth). On chromosome 5, the most significantassociation influenced the lean:bone ratio at the forerib jointand was flanked by markers DIK4782 and BR2936. Other highlysignificant associations were detected on chromosomes 10 (estimatedsubcutaneous fat percentage), 11 (total saleable meat proportion),16 (prehousing growth rate), and 22 (bone proportion at theleg joint). These results provide a useful starting point forthe identification of the genes associated with traits of directinterest to the beef industry, using fine mapping or positionalcandidate gene approaches.

Key Word :
carcass composition, cattle, growth trait, quantitative trait loci

Volume 87, Number 1, January 2009