본 연구는 국내 실정에 맞는 적정 TDN/CP 비율을 결정하기 위하여 4.6:1(T1)과 4.3:1(T2)의 비율로 생후 13개월령 육성우에게 급여하여 영양소 섭취량, 소화율, 반추 위액 특성 및 혈액조성에 대하여 조 사하였다. 건물 섭취량은 9.0kg/day로 동일하였으며, 조단백질 섭취량은 T1이 1.34kg/day, T2가 1.45kg/day로 T2가 조금 높았으나 유의적인 차이는 없었다. 섬유소 섭취량과 소화율은 T1이 조금 높은 경향을 보였으나 유의적인 차이는 없었다. 사료 섭취 후 4시간째 위액의 pH, ammonia-N, VFA 농도 를 비교한 결과 처리구간 유의적인 차이를 나타내지 않았다. 전반적인 VFA 수치는 TDN/CP 비율에 따 라 큰 영향이 없었으나 T1 처리구에서 iso-butyrate, iso-valerate 및 A/P ratio가 유의적으로 높은 결과를 보였다(p<0.05). 혈액 특성에는 처리구간 유의적인 차이를 나타내지 않았다. TDN/CP 비율이 4.3:1과 4.6:1 수준은 반추위 특성에 큰 영향을 미치지 않았지만, 소화율과 비교하였을 때 생후 13개월 령 육성우 시기에는 섬유소 섭취량과 소화율이 증가되는 4.6:1 수준이 보다 적합할 것으로 판단된다.

In this study, the effect of energy and protein ratio on the nutrient availability and body weight gain was determined to find the proper nutrient level for the stage of replacement dairy heifers before fertilization at approximately 12~24 months old after birth. Dry matter intake showed that the TDN/CP rate of T1 (5.0:1), T2 (4.5:1) and T3 (4.0:1) resulted in similar values. Among feces, the ash content of T1 was 11.07%, which was significantly (p < 0.05) higher than that of T3 (9.69%). It was also significantly (p < 0.05) higher than that of T2 (10.32%). When the TDN/CP rate was increased, the ash content in the feces was also increased. Regardless of the initial weight, weight gain was increased significantly as the CP rate in the feed was increased on the 30th day. On the 60th day, T2 showed the highest rate of gain (p < 0.05). As the TDN rate was decreased or the protein rate was increased, weight gain was significantly (p < 0.05) increased. Regarding GPT level in the blood after finishing the test, T1 and T3 (112.6, 88.3 u/l) showed significantly (p < 0.05) higher value than T2 (50.9 u/l). For phosphorus level, T1 (46.3 mg/dl) showed significantly (p < 0.05) higher value than other treatments. For HDL cholesterol level, T2 (145.2 mg/dl) had significantly (p < 0.05) higher level than T1 (121.0 mg/dl) or T3 (132.3 mg/dl). For triglyceride levels, T3 (40.6 mg/dl) had significantly (p < 0.05) higher value than T1 (20.7 mg/dl) and T2 (29.0 mg/dl). For other blood parameters including BUN concentration, there were no significant (p > 0.05) difference among treatments. As a result, although feed intake and weight gain with TDN/CP rate of 4:1 showed best results, considering the excess body fat accumulation possibilities or blood metabolism, it seems 4.5:1 ratio is most appropriate.