Effect of body condition score and age on slaughter performance and carcass characteristics of Nellore brown rams

Abstract

The study investigated the influence of Body Condition Score (BCS), which serves as a practical indicator of nutritional status and fat reserves in sheep, on reproductive efficiency, health, and meat production, particularly in tropical regions like India, where Nellore Brown sheep contribute to rural economies. The experiment was conducted from January to April, 2023. Sixty rams were purposively selected and divided into two age groups: 1-year-old (n=30) and 2 to 3-year-old (n=30), further stratified by BCS (2.0, 3.0, 4.0, 5.0) on a 5-point scale with six rams per subcategory. Animals received a standard diet of 50% green fodder, 30% dry fodder, and 20% concentrate to preserve natural BCS variation. Pre-slaughter live weights were recorded after 12 hours of fasting. Different components were weighed post-slaughter. Data were analyzed via two-way ANOVA in SPSS 25.0, with Duncan's test (p<0.05) and Pearson correlations. Live weight increased with BCS and age, peaking at 35.2 ± 1.1 kg in 2 to 3-year-olds at BCS 5.0. Drained blood averaged 1.80 ± 0.1 kg in higher BCS groups, correlating positively with body mass (r=0.72, p<0.01). Skin weight was higher in older rams (3.5 ± 0.2 kg at BCS 5.0), reflecting hide development. GI tract contents showed age effects (4.20 ± 0.3 kg vs. 3.20 ± 0.2 kg) but not BCS. Viscera weight increased with BCS, reaching 3.70 ± 0.2 kg in mature rams at BCS 5.0. Average weight of head and legs was 3.90 ± 0.2 kg in older groups. Hot carcass weight and dressing percentage correlated strongly with BCS (r=0.85, p<0.01), maximizing at 17.1 ± 0.7 kg and 48.5 ± 1.2% in 2 to 3-year-olds at BCS 5.0, comparable to reports in indigenous breeds (47-50%). Results confirmed BCS as a reliable predictor of slaughter performance, with optimal scores (4.0-5.0) enhancing yields, particularly in mature rams due to greater fat and muscle deposition. Age interactions were significant (p<0.05), underscoring nutritional management to mitigate low-BCS losses (15-20%). Integrating BCS assessment could optimize selective breeding and feeding in Indian sheep farming, though breed-specific extrapolations warrant caution due to genetic and environmental variations. Limitations included small subgroup sizes; future research might incorporate ultrasound for fat depth.