This study was conducted to investigate the optimal CP level in growing goat kids. Forty male goats were divided into four treatment groups fed diets containing CP 12, 14, 16, and 18% of concentrate feed, and rice straw, respectively. Results are summarized as follows. Average daily gain's (ADG) of groups fed diets with CP 14% and CP 18% were 84.0 and 83.0 g/d each, which were higher than group fed diets with CP 12% grown at 69.2 g of ADG (P<0.05). Daily feed intakes of concentrate and rice straw were 590 g and 45 g each and there was no difference found between treatments. The amounts of feed required for body weight gain(g) were similar in the range of 7.0 7.3 for groups fed diets with CP 14%, 16% or ～ 18%. But the group fed diets with CP 12% required somewhat more feed for gain at 8.8 g. Dressing percentage of groups fed diet with CP 12% was 61.7%, which was higher than groups fed diets with CP 14% or CP 18% (P<0.05) but similar to that fed diet with CP 16%. Meat percentage from goats fed diet with CP 16% was 51.7%, which were higher than goats fed diets with CP 12% or CP 14% (P<0.05). Fat deposition of CP 12% group was higher than the other groups (P<0.05). Percentage of bone weight averaged 17.0% without any difference among treatment groups. Shear force and cooking loss, which are physical properties of goat meats, were lower in CP 16% and CP 14% groups than the other two groups. Water holding capacity of goats meats from CP 16% was higher than those from CP 18% group (P<0.05). Results from panel test showed that juiciness of meats from CP 16% group was higher than those from CP 12% group (P<0.05). Meats from CP 16% also was tested to be more tender than meats from the other groups. Results from this work suggest that the optimum crude protein level in growing goat's concentrate is 14 16% and that increase above this level seems not to improve meat production.

Competing interestsNo potential conflict of interest relevant to this article was reported. Funding sourcesState funding sources (grants, funding sources, equipment, and supplies). Include name and number of grant if available.Not applicable.

We investigated the effect of energy levels on growth performance, carcass characteristics, and fatty acid composition of Holstein steers at different slaughter ages. Forty Holstein steers with an average body weight (BW) of 234.21 ± 7.42 kg and 7.78 ± 0.22 months were randomly allocated to two experimental groups; a 22-month-old experimental group and a 24-month-old experimental group. Total digestible nutrients (TDN) for each group were set to 70% (T1) and 72% (T2) during fattening phase and 74% (T3) and 76% (T4) for the finishing phase, respectively. No difference was observed in the final BW between the experimental groups during the fattening phase. However, in the finishing phase, the final BW of T4 (820.31 kg) group was significantly higher than that of T1 (745.57 kg; p < 0.05). The average daily gain (ADG) of T2 group in the finishing phase and overall period were 1.27 kg and 1.26 kg, respectively, which were significantly higher than those of T1 (1.11 kg and 1.12 kg; p < 0.05). The feed conversion ratio (FCR) and TDN conversion ratio of T2 group in the finishing phase also decreased by 10.23% and 7.73%, respectively, compared to those of T1. The cold carcass weight of T4 group was significantly higher ( p < 0.05) than that of T1, whereas back fat thickness, longissimus area, and marbling score were not significantly different among groups. No differences were observed in physicochemical characteristics of the carcass including moisture, crude protein, and crude fat content among groups. However, the composition of fatty acids differed significantly between the groups. The content of C18:0 was significantly lower ( p < 0.05) in T4 than in T1 group, and the content of C18:2 was higher in T4 than in T1 and T3 ( p < 0.05). Therefore, feeding Holstein steers at a high-energy feeding level during the fattening and finishing phases improves ADG and reduces the slaughter age from 24 months to 22 months.