PAG-V: S13 - LOCALISATION OF QUANTITATIVE TRAIT LOCI (QTL) FOR GROWTH TRAITS IN <i>Bostaurus X Bos indicus</i> CATTLE

Plant & Animal Genome V Conference

Town & Country Hotel, San Diego, CA, January 12-16, 1997.

S13

LOCALISATION OF QUANTITATIVE TRAIT LOCI (QTL) FOR GROWTH TRAITS IN Bostaurus X Bos indicus CATTLE

HETZEL, JAY, G. Davis, N. Corbet, S. Scacheri, C. Mayne, J. Scott, R. Stevenson
CSIRO Tropical Agriculture, Molecular Animal Genetics Centre, Gehrmann, Laboratories, University of Queensland, Brisbane, Australia 4072; Cattle, and Beef Industries CRC for Meat Quality

Three chromosomal regions which have significant effects on growth in cattle have been identified using multipoint interval mapping in half-sib families. Two first cross Charolais x Brahman bulls, with a common Charolais sire, were mated to cows which were a multi-breed composite of equal parts Hereford, Shorthorn, Africander and Brahman (AXBX). There were 220 and 132 progeny born alive in the two families over three years of mating. Bull calves were castrated at 3 months of age. The progeny were weaned at 200 days of age and grown out on pasture in the dry tropical region of Central Queensland. Weights were taken at birth (0M) and at subsequent six monthly intervals (6M, 12M, 18M). Growth rates were calculated preweaning (0-6M), post-weaning (6-18M) and during the dry season (6-12M) and wet season (12-18M). Progeny were genotyped for a total of 134 markers chosen from the genetic map developed on the International Bovine Reference Panel. The markers spanned 80% of the genome with between 3 and 10 markers per chromosome at an average spacing of 26 cM. The traits were individually examined by sequentially analysing each chromosome within each sire family using the ANIMAP interval mapping software. Chromosome 26 was not analysed since only a single marker was available; the pseudo-autosomal region of the sex chromosomes was treated as another autosome. Analyses of the eight growth traits revealed a total of eight associations with lod scores greater than or equal to 2.4, though only four chromosome regions were represented. One region on chromosome 19 was significant for three growth traits (6M, 12M, 18M) and two other regions on chromosomes 14 and 21 were significant for two traits, (0M, 6-12M) and (0M, 6M) respectively. Although there is some effect of part/whole relationships between traits, the results indicate that relatively few chromosome regions are responsible for a large amount of the variation in growth observed in this cross.