PSX-19 Factors affecting growth and carcass trait performance of Canadian heavy lambs

Abstract

Abstract The profitability of meat lamb production is strongly dependent on growth and carcass trait performance of market lambs. The objective of this research was to test the significance of non-genetic factors on growth, ultrasound, and carcass traits of Canadian heavy lambs. Hot carcass weight (HCW, kg), fat depth at the GR site (FATGR, mm), average carcass conformation score (CONF, points), and total carcass value (PRICE, $CAD) were measured for 8,865 purebred lambs marketed through Quebec’s Heavy Lamb Sales Agency. Corresponding management information and growth trait records for over 19,000 animals with carcass records and their relatives were extracted from the Canadian Sheep Genetic Evaluation System. Single-trait mixed linear models in SAS were used to test the significance (P < 0.05) of various non-genetic effects, after a Scheffe adjustment for multiple comparisons. All models included categorical fixed effects of sex (male or female), breed (Hampshire, HA; Suffolk, SU; Canadian Arcott, CD; Polled Dorset, DP; Rideau Arcott, RI; Polypay, PO), dam age at parity (1 to 7+ years), and birth and rearing type (born as single, twin, or triplet and more, and reared as single or multiple), and a random effect of contemporary group. Linear covariates of slaughter age or carcass weight were included in the carcass trait models, while a scanning weight covariate was used for ultrasound trait models. Male lambs were found to be significantly heavier during growth, had greater HCW and PRICE, and lower FATGR and CONF than female lambs. As expected, terminal breeds (HA, SU, CD) tended to have greater growth, greater HCW and PRICE, and lower FATGR than maternal (DP, RI, RV, PO) breeds. This information could be utilized by Canadian sheep producers to manage their flocks to maximize the revenue of lambs marketed through price grid classification systems.