Effects of Crude Protein Levels in Total Mixed Rations on Growth Performance and Meat Quality in Growing Korean Black Goats

Abstract

This study was carried out to investigate effects of crude protein (CP) levels in total mixed rations (TMR) on growth performance and meat quality in growing Korean black goats. Thirty-six 6-month-old growing black male goats (initial body weight = 17.95±0.13 kg) were used. The goats were randomly divided into four treatments and 9 animals were allotted to each treatment. In terms of treatments, CP levels in TMR were 14, 16, 18, and 20% of dry matter (DM) and all diets were isocaloric (2.4 Mcal ME/kg DM). The experiment lasted for 20 weeks with a 15-day adaptation period. After the end of the trial, five goats from each treatment were slaughtered to measure carcass characteristics and meat quality. Average daily gain (ADG) significantly (p<0.05) increased as dietary CP levels increased, but the highest ADG was found on the 18% CP treatment. The higher CP levels in TMR significantly (p<0.05) decreased feed conversion ratio, but the lowest ratio was on the 18% CP treatment, suggesting a higher bioavailability of nutrients by balanced energy and protein levels on this treatment. There was no significant difference in dressing percentage among treatments, but there was a tendency for levels more than 16% CP in TMR to have a comparatively higher dressing percentage than the 14% treatment. The percentages of meat, fat and bone were not significantly influenced by dietary CP levels. Dietary CP levels did not influence chemical composition of goat meat. Furthermore, there was no significant difference among treatments in any of the sensory parameters except for tenderness. Tenderness was similar for 18 and 20% treatments, which were significantly (p<0.05) higher than the 14% treatment. The results from this study suggested that an adequate CP level in TMR for achieving optimal growth performance and meat quality of growing Korean black goats might be 18% of DM, and that dietary CP level above 18% seemed not to further increase growth performance and meat quality.