Relationships between live weight, body condition, dimensional and ultrasound scanning measurements and carcass attributes in adult Angora goats

Abstract

Real-time ultrasound scanning is an accurate non-invasive technique used to improve quality in sheep, cattle and pig meat production but has been overlooked in meat production from heavy goat carcasses. The aims of this study were to: determine subjective and objective carcass attributes of 6year old Angora castrate goats prior to and following slaughter; and determine the relationships between carcass attributes, bodyweight, body condition score (BCS), body dimension measurements and ultrasound measurements using multiple regression modelling. Key attributes were: on-farm bodyweight (range 35–77kg), BCS (1, very thin to 4.3, fat), dimensional frame measures (wither height, heart girth, anterior-posterior circumference, body volume (circumference×girth)), carcass weight (range 11.6–33.2kg), GR tissue depth of carcasses (1–27mm) and the ultrasound measurements of eye muscle depth (EMD, 17–35mm) and subcutaneous fat depth (SFD, 1–6mm). Goats from three genetic backgrounds were grazed on pasture together for 6 years. In the three months preceding slaughter the goats grew from an average live weight of 50.7kg gaining live weight at an average of 117g/d to reach an average live weight of 62kg. There were moderate correlations between all measurements. BCS accounted for 55.1% of the variance in carcass weight, 51.3% of the variance in EMD, (3.2% more than did GR tissue depth) and 59.9% of the variance in SFD. Live weight accounted for 83.8% of the variance in carcass weight. The best prediction equation for carcass weight included terms for live weight, SFD, EMD and sire, accounting for 91.5% of variance. Body dimensional measurements were not as useful as BCS in predicting carcass weight, with the best, body volume, accounting for 5% less of the variance than live weight. The best prediction for the EMD included terms for BCS and carcass weight, accounting for 61% of variance. GR tissue depth was primarily associated with SFD, and in combination with carcass weight and BCS explained 71.9% of the variance. In relation to predicting carcass traits, girth accounted for more of the variance in EMD, SFD and GR tissue depth than wither height or body circumference. If breeders aim to alter the EMD and SFD of Angora goats then ultrasound scanning provided better estimates compared with relying on live weight with or without body condition scoring. Both EMD and SFD were also in the best model for predicting carcass weight. BCS was a useful on-farm measurement for estimating carcass attributes but girth was not as useful as body volume in explaining the variance in live weight.