Quantitative trait loci for live animal and carcass composition traits in Jersey and Limousin back-cross cattle finished on pasture or feedlot.

A quantitative trait locus (QTL) study was carried out in two countries, recording live animal and carcass composition traits. Back-cross calves (385 heifers and 398 steers) were generated, with Jersey and Limousin breed backgrounds. The New Zealand cattle were reared on pasture to carcass weights averaging 229 kg, whilst the Australian cattle were reared on grass and finished on grain (for at least 180 days) to carcass weights averaging 335 kg.

Genetic variation of plasma insulin-like growth factor-1 in young crossbred ewes and its relationship with their maintenance feed intake at maturity and production traits.

The genetic variation of plasma IGF-I in crossbred ewe lambs postweaning was evaluated together with its potential use as a physiological marker for selection in meat sheep. Genetic variation for IGF-I was analyzed among 1,246 young crossbred ewes that were the progeny of 30 sires from various maternal breeds and Merino dams. The estimate of heritability of IGF-I was 0.

Reproductive performance and genetic parameters in first cross ewes from different maternal genotypes.

The reproduction of 2,846 crossbreed ewes with 7,899 records is reported. The ewes were progeny of mainly Merino dams and 91 sires from several maternal sire breeds including Border Leicester, East Friesian, Finnsheep, Coopworth, Corriedale, Booroola Leicester, and several others. There were 3 cohorts of ewes at each of 3 sites that were bred naturally to meat-type rams for each of 3 yr to evaluate reproduction and lamb production.

Breed variation and genetic parameters for growth and body development in diverse beef cattle genotypes.

Conformation scores can account for more than 20% of cattle price variation at Australian livestock sales. However, there are limited available references which define genetic factors relating objective live developmental traits to carcass composition. Weaning and post-weaning weight, height, length, girth, muscle (ratio of stifle to hip width) and fat depth of 1202 progeny from mature Hereford cows (637) mated to seven sire breeds (Jersey, Wagyu, Angus, Hereford, South Devon, Limousin and Belgian Blue) were examined for growth and development across ages.