Effects of Deletion of Ca Supplement (limestone) on Growth and Beef Quality in Hanwoo Finishing Steers

A study was conducted to determine the effects of feeding a diet containing no Ca supplement (limestone) during the late finishing period on growth, marbling and serum 1,25-dihydroxy vitamin $D_3$ level in Korean native cattle. Twenty-four steers (20${\sim}$24 mo of age) were divided into two groups of 12 each: one group assigned to a control diet (concentrates containing 2.5% limestone) and the other to a diet containing no calcium supplement. They were allowed to have free access to diets (concentrates and orchard grass hay) and water during the entire feeding period (223 d). Serum $Ca^{2+}$, Ca and P concentrations were not influenced by diets, but serum 1,25-dihydroxy vitamin $D_3$ concentrations determined 2 or 6 mo after the beginning of feeding the experimental diets were higher (P<0.01) in steers fed the diet without Ca supplement than in those fed the control diet (78.3 vs 51.7 and 80.3 vs 51.1 pg/mL, respectively). Steers fed the diet without Ca supplement tended to have a higher intake of concentrates, but a lower intake of hay, compared to those fed the control diet. Average daily gain was higher (P<0.05) in steers fed the diet without Ca supplement than in those fed the control diet. Feeding the diet without Ca supplement remarkably (P<0.01) increased the marbling score (5.1 vs 2.2) and the muscle (M. longissimus dorsi) fat content (10.2 vs 6.7%) with a concomitant decrease in moisture content (67.6 vs 70.4%), compared to feeding the control diet. Ribeye area was increased (77.2 vs 82.8 $cm^2$) with the diet without Ca supplement, compared to the control diet (P<0.05). Meat color, pH and water-holding capacity in longissimus muscle were not different between the two groups. The Warner-Brazler Shear (WBS) force of the longissimus muscle was slightly (P=0.08) lower in steers fed the diet without Ca supplement than in steers fed the control diet (2.9 vs 3.2 kg/1.27-cm diameter core). Sensory evaluation showed that feeding the diet without Ca supplement slightly (P<0.05) improved tenderness (4.9 vs 4.5) and flavor (4.9 vs 4.6), compared to feeding the control diet, but juiciness was not affected by diets. Results showed that deletion of Ca supplement from finishing diets is beneficial, increasing growth and marbling partly through an increased energy intake and induced 1,25-dihydroxy vitamin $D_3$ synthesis that may increase intracellular $Ca^{2+}$ concentration and in turn fat synthesis.

한우 비육후기 사료에 칼슘 첨가제(석회석) 제거가 성장 및 육질특성에 미치는 영향

이 연구는 소 비육후기에 칼슘제(석회석)를 첨가하지 않은 사료의 급여가 성장율, 근내지방도 및 혈청 1,25-dihydroxy vitamin $D_3$ ($1,25(OH)_2D_3$) 함량에 미치는 영향을 구명하기 위하여 수행되었다. 거세 한우 24두(20${\sim}$24개월령)를 12두씩 대조구(석회석 2.5% 함유 농후사료)와 칼슘제 무첨가구(석회석 0%)로 배치하여 223일 동안 사료(농후사료 및 오차드그라스 건초)와 물을 무제한 급여하였고, 사양시험이 완료된 후 도축하여 육질을 평가하였다. 혈청 $Ca^{2+}$, Ca 및 P 함량에는 처리 간 차이가 없었으나 (P>0.05), 1,25(OH)2D3 함량은 시험 시작 후 2 또는 6개월째 모두 칼슘제 무첨가구가 대조구보다 (각각 78.3 vs 51.7 또는 80.3 vs 51.1 pg/mL) 높았다 (P<0.01). 칼슘제를 첨가하지 않은 사료를 급여한 비육우가 대조구보다 농후사료 섭취량은 증가하고 건초 섭취량은 감소하는 경향을 보였다. 일당증체량은 대조구보다 칼슘제 무첨가구에서 높았다(P<0.01). 등심단면적(82.8 vs 77.2 $cm^2$), 근내지방도(5.1 vs 2.2) 및 지방 함량(10.2 vs 6.7%)이 칼슘제 무첨가구가 대조구보다 높았고 (P<0.05), 수분 함량(67.6 vs 70.4%)은 낮았다 (P < 0.05). 등심 육색, pH 및 보수력에서는 처리 간 차이가 없었으나 전단력에서는 칼슘제 무첨가구에서 (2.9 vs 3.2 kg/1.27-cm diameter core) 약간 낮게 (P = 0.08) 나타났다. 관능평가에서는 칼슘제 무첨가구가 대조구보다 연도 (4.9 vs 4.5) 및 향미(4.9 vs 4.6)가 약간 개선되었으나 (P<0.05) 다즙성에서는 처리간 차이가 없었다 (P>0.05). 본 연구결과는 비육후기에 칼슘제(석회석)를 첨가하지 않은 사료의 급여는 에너지 섭취의 증가 또는 1,25$(OH)_2D_3$의 합성 촉진을 통하여, 근내지방합성이 증가되어 성장율 및 근내지방도를 개선한다는 것을 제시하였다.