Effect of Red clay(Hwangto) on Growth Performance and Carcass Characteristics in Growing-Fattening Hanwoo Steers

This study was conducted to examine the effects of Red clay(Hwangto) as feed additives with 26 Hanwoo steers at two regions for 540 days from six to 24 months of age on feed efficiency, meat quantity and meat quality. Feeding trial 1 was conducted with two treatment groups by five heads/treatment which were T1(Control) and T2(Control+ad libitum Hwangto) at National Livestock Research Institute. Feeding trial 2 was conducted with four treatment groups by four heads/treatment which were T1(Control), T2(Control+2% Hwangto), T3(Control+5% Hwangto) and T4(Control+ad libitum Hwangto) at a private Hanwoo breeding farm. In feeding trial 1, average daily gains by growing, fattening, finishing and over-all periods were 0.572, 0.866, 0.869 and 0.769kg in T1, and 0.537, 0.904, 0.857 and 0.766kg in T2, respectively. Average daily gain for growing and finishing period was high in T1 but in T2 for fattening period, which were not statistically significant. Also concentrates and TDN intakes per kg gains were not statistically significant by treatments. In carcass characteristic, dressed carcass and red meat percentage were high in T1 but in T2 for retailed cut percentage without significant difference. The yield index and shear force was 69 and 70, 4.4 and 6.1 kg/$cm^2$ in T1 and T2, respectively. In palatability traits, the panel test scores of juiciness, tenderness and flavor were 4.08 and 4.64, 3.42 and 3.96, 4.58 and 4.80 in T1 and T2, respectively. which showed a tendency to improvement in Hwangto feeding groups. In feeding trial 2, the range of average daily gains were 0.656(T6) to 0.772(T3), 0.937(T6) to 1.009(T5), 0.592(T3) to 0.675kg(T6) in growing, fattening and finishing period, respectively. Although it was high in T3, T5 and T6 at growing, fattening and finishing period, respectively, it was not significantly different by treatments. The ranges of concentrates and TDN intakes per kg gains were 8.71 to 9.50(average 9.05) and 7.52 to 7.64kg(average 7.55kg), they all were lower in Hwangto feeding groups than in control about 4.5 to 8.3% and 1.2 to 1.6%, respectively. In carcass characteristics, back-fat thickness, loin eye muscle area and yield index were not difference by treatments, but marbling scores were high in T5 and T6 than in percent. Summarizing above results, it may be concluded that the use of unprocessed Hwangto as feed additives for growing-fattening steers seems to improve meat quality but not red meat quantity and feed efficiency, and may be required to feed ad libitum during the finishing period.

육성비육 거세한우에 대한 황토 급여가 성장 및 도체특성에 미치는 효과

육성비육우에 대한 황토급여 효과 구명을 위하여 거세한우 송아지 10두(평균체중 : 144.7kg)를 대상으로 황토급여 유무에 따른 2개 처리(T1 : 황토 무급여, T2 : 황토 자유채식) 와 황토급여 수준에 따른 4개 처리(T3 : 황토 무급여, T4 : 황토 2% 첨가, T5 : 황토 5% 첨가, T6 : 황토 자유채식)를 두어 6개월령부터 24개월령까지 540일간 사양시험을 실시한 결과를 요약하면 다음과 같다. 시험 1에서, 일당증체량은 육성기 및 비육후기에는 황토 무급여구가, 비육전기에는 황토 자유채식구가 우수하였으나 전기간 동안에는 황토급여 유무에 따른 차이가 없었고, 1kg 증체당 소요된 농후사료 및 TDN량도 황토급여 유무에 따른 뚜렷한 차이는 없었다. 도체조사 결과, 도체율, 정육율 및 거래정육율은 황토급여 유무에 따른 뚜렷한 차이가 없었으나 육량지수, 전단력 및 관능검사의 각 항목 등은 황토급여시 개선되는 경향이었다. 그 밖에 경제성분석결과 처리구별 소득은 처리구간에 따른 뚜렷한 차이는 없었다. 시험 2에서, 일당증체량은 육성기에는 황토 무급여구가, 비육전기에는 황토 5%구가 그리고 비육후기에는 황토 자유채식구가 우수하였으나 전기간에는 황토급여 수준에 따른 뚜렷한 차이가 없었으나, 1kg 증체당 소요된 농후사료 및 TDN량 관행사육구에 비해 황토 급여구에서 각각 4.5-8.3% 및 1.2-1.6% 적게 소요되었다. 도체조사 결과 등지방두께, 배최장근단면적 및 육량지수는 황토급여 수준에 따른 뚜렷한 차이가 없었지만, 근내지방도는 황토 5% 및 자유채식구에서 높은 것으로 나타났고, 황토를 자유채식시 관행사육에 비해 소득이 15.5% 증가하는 것으로 나타났다. 이상과 같은 결과를 요약해 볼 때 거세한우 비육우에 대해 가공하지 않은 황토 급여시 육량 및 사료이용성에는 뚜렷한 효과가 없는 반면 육질개선에는 다소 영향을 미치는 것으로 나타났다. 따라서 황토급여시에는 비육후기에 자유채식의 형태로 급여하되, 이용성 증대를 위해 미세입자로 하거나 지장수 형태로 급여하는 것이 바람직 할 것으로 판단된다.