Ultrasound measurements of live and carcass traits in Tswana goat kids raised under semi-intensive system in South-eastern Botswana

Abstract

The aim of this study was to characterise ultrasound measurements of live and carcass traits in intact males, females and castrated Tswana goat kids from birth to 12months of age raised under semi-intensive system in South-eastern Botswana. Measurements were recorded in 15 castrates, 15 intact males and 15 female Tswana goat kids randomly selected at birth. Ultrasonic fat and muscle depths were measured at the first, third/fourth, sixth/seventh, ninth/tenth and 12th/13th thoracic; first, third and fifth lumbar and first, second/third and fourth/fifth sternal vertebrae, fortnightly for the first 6months and then monthly for the remaining 6months. The animals were stunned and humanely slaughtered at 12months of age, and ultrasound and shatterproof ruler were used to measure fat and muscle depths on the carcasses at similar sites as on live animals. A real-time B-mode ultrasound scanner fitted with LV2-1 probe operating at 7.5MHz (Explorer V5 Vet Laptop B-Ultrasonic Scanner UMC Technology Development Co., Ltd, China) was used to predict ultrasound measurements on live animals and their carcasses. Data were analysed using general linear model in statistical analysis system. Muscle depth measurements increased significantly (p < 0.05) with age in all sites of measurements. However, there was no significant difference between the sexes at different sites of muscle depth measurements at the same age. Muscle depth at the sternal vertebrae was significantly deeper (almost 55mm at 12months of age) than 16mm at thoracic and 16mm at lumbar vertebrae at 12 and 8months of age, respectively. No subcutaneous fat depth measurements were recorded in the lumbar vertebrae (0.00 ± 0.00) and the thoracic (0.00 ± 0.00) regions in all sex groups. However, fourth and fifth sternal vertebrae showed considerably deeper amount of subcutaneous fat suitable for taking fat measurements as age increases (2.07 ± 0.23mm females, 1.50 ± 0.43mm intact males and 1.80 ± 0.38mm castrates) at 12months of age. All correlations between live and carcass ultrasound measurements and also between ultrasound carcass and ruler measurements were very high (r (2) = 0.96 to 1.00) for all the sexes indicating that live ultrasound measurements are suitable for use in this meat breed. More research is needed to evaluate the relationships between live ultrasonic measurements and carcass yield in the different sexes of Tswana goat kids.