This study investigated the effects of different protein levels on growth performance, feed efficiency, and morphological traits in female and male Boer × Korean native crossbred goats (Capra hircus) raised in Korea. A total of twenty-four goats (12 per sex) with an average age of seven months were included in the experiment. The initial body weights (BW) were 31.0 ± 0.6 kg for females and 27.4 ± 1.5 kg for males. A randomized block design was used with three dietary crude protein (CP) treatments: 15% (T1), 18% (T2), and 21% (T3). The results demonstrated that, in female goats, no significant differences (p>0.05) were observed in most growth parameters, except for dry matter intake (DMI), which was significantly higher in T2 and T3 (p<0.05). The total weight gain (TWG) was 2.2 kg in both T1 and T2, and 2.8 kg in T3. The average daily gain (ADG) in females reached 82 g/d in T3, significantly higher than the other. In male goats, DMI was also greater in T2 and T3 compared to T1, with the highest TWG (4.4 kg) and ADG (126.9 g/d) recorded in T3, surpassing the other treatments. Regarding morphological traits, female goats in T3 exhibited significantly greater body length (66.9 cm), withers height (62.8 cm), and chest girth (19.3 cm) compared with T1 and T2 (p<0.05). In contrast, male goats in T2 showed superior body length (65.6 cm), chest width (20.1 cm), and chest girth (78.5 cm) (p<0.05). In conclusion, the study indicates that higher protein levels (21% CP) enhance growth performance and morphological development in female goats, whereas a moderate level (18% CP) appears to be more effective for male goats. These findings suggest that protein requirements differ by sex, and sex-specific feeding strategies should be considered to optimize growth and body conformation in crossbred goats.

본 시험은 산양유 생산을 위해 유기사료를 이용하여 유산양의 적정 에너지 및 단백질 공급 수준과 조농비율을 결정하기 위하여 비유중기 Saanen종 유산양 4두( BW)를 이용하여 라틴방각법으로 실시하였다. 대사에너지 공급수준과 단백질 공급수준을 10.59 (T1), 10.14 (T2), 9.45 (T3) 및 8.75 (T4) MJ/kg과 11.90 (T1), 12.73 (T2), 15.19 (T3) 및 16.60% (T4)로 달리하였으며, 조농비율은 49

본 시험은 산양유 생산을 위해 유가사료를 이용하여 유산양의 적정 에너지 및 단백질 공급 수준과 조농비율을 결정하기 위하여 비유중기 Saanen종 유산양 4두(57.5土10.8 kg BW)를 이용하여 4x4 라틴방각법으로 실시하였다. 대사에너지 공급수준과 단백질 공급수준을 10.59 (T1), 10.14 (T2), 9.45 (T3) 및 8.75 (T4) MJ/kg과 11.90 (T1), 12.73 (T2), 15.19 (T3) 및 16.60% (T4)로 달리하였으며, 조농비율은 49:51 (T1), 59:41 (T2), 74:26 (T3) 및 90:10 (T4)의 네 처리구로 나누었다. 사료 섭취량 및 체중은 모든 처리구 사이의 유의한 차이가 없었다. 유량은 T3구에서 가장 높았으며, T2 및 T4구와 비교 하여 유의하게 높게 나타났다(p<0.05). 유지방 함량과 생산량은 T4구에서 다른 처리구와 비교하여 가장 낮았다(p<0.05). 유단백질과 유당 생산량은 T1 (61.29 및 70.95 g/일)과 T3 (60.52 및 75.82 g/일)구에서 T2 (50.49 및 59.64 g/일)와 T4 (52.49 빛 59.82 g/얼)구와 비교하여 유의하게 높게 나타났다. 결과적으로 유산양의 유생산성을 극대화시커기 위해서 에너지 공급수준은 최소 9 MJ/kg 이상과 단백질 공급수준은 최소 15% 이상을 공급해 주어야할 것으로 기대된다.

The present study was conducted to investigate effect of dietary protected amino acid on milk yield and composition in dairy cow using meta-analysis. Total 21 research papers were employed in analysis, and mixed model was used for the analysis of effects. Effect of protected methionine (PM) and combination of protected methionine and lysine (PML) were investigated under two different levels of dietary crude protein (CP, <18% and >18%). For performance of dairy cow, milk yield, milk composition including milk fat and protein content and yield and 4% FCM (fat corrected milk) production were used for analysis. In case of milk yield, a trend of increment was found at PM supplementation at low CP (P=0.055). However, the effect of PM at high CP was detected as not significant (P>0.05). In case of milk protein, inclusion of PM at low CP showed significant decrement (P<0.05). However, there was no significant effect of MP on milk protein at high CP (P>0.05). Supplementation of MP at high CP level showed significant increment of milk fat (P<0.05). MP supplementation represented significant increment of 4% FCM production (P<0.05) regardless of dietary CP levels. Effects of PML on milk yield and composition at both of low and high dietary CP were not significant in this study. However, it seem to be that there was a possible positive effect of MPL application at high dietary CP on performance of dairy cow.