The Effects of Processing Methods of Corn on In sacco Starch and Protein Degradability in the Rumen

The objective of this study was to examine the effects of processing methods of corn grains on protein and starch degradability in the rumen by three ruminally cannulated dry Holstein cows. The corns for these experiments were untreated; whole corn L(density; 660 g/$\ell$), whole corn H(density; 740 g/$\ell$), and treated by four different types: Ground corn, 3.8 mm, 2.8 mm, and 1.5 mm flaked corn. The results obtained were summarized as follows: For 48 hrs, the protein degradabilities were high in order, ground corn, 1.5 mm, 2.8 mm, and 3.8 mm flaked corn(82.6, 76.5, 64.5, and 33.9%, respectively). Flaked corn grains were degraded lower than ground corn. However, as increasing the processing degree of flaking, the protein degradabilities, from 4 hrs to 48 hrs, were increased. The starch degradabilities on 48 hrs were higher in 1.5 and 2.8 mm flaked corns, ground corn, 3.8 mm flaked corn(99.1, 91.5, 89.5, and 68.9%, respectively) than whole corn L(32.0%) and whole corn H(20.5%)(P<0.05). By increasing the processing degree of flaking, the protein degradabilty between 2.8 mm and 3.8 mm was increased significantly from 68.9% to 91.5%, however, that of 1.5 mm flaked corn, processed thinner, tended to be increased slightly, but was not significantly different. From 12 hrs to 24 hrs, whole corn L was degraded little more than whole corn H in starch, was not significantly different. However, after 48 hr incubation in the rumen, whole corn L was degraded more 50% than whole corn H(P<0.05). The value of degradation parameter “a” of protein was lower in all flaked corns than in ground corn. In contrast, the value of degradation parameter “a” of starch was significantly higher in all flaked corns than in ground corn(P<0.05). It seemed that by flaking the corn grains, starch particles were gelatinized, and then, starch was degraded more rapidly, while protein was degraded more slowly. Referring to these kinds of physical characteristics of grain sources in ruminal degradabilities, it is possible to synchronize the fermentation of nitrogen and carbohydrate sources, in formulating the cattle diets.

옥수수 가공방법이 In sacco 전분 및 단백질 분해율에 미치는 영향

옥수수 알곡의 무처리(통 옥수수 2종) 및 가공방법(분쇄, flake 3.8mm, 2.8mm 및 1.5mm)이 in sacco 방법에 있어 반추위 내에서의 전분 및 단백질 분해율에 미치는 영향을 측정하고자 반추위에 캐뉼라(cannulae)가 장착된 홀스타인종 건유우 3두를 공시축으로 하여, 본 시험을 수행하였는데 그 결과를 요약하면 다음과 같다. 1)48시간대에서의 전분 분해율은 1.5mm, 2.8mm flake, 분쇄 옥수수, 3.8mm flake, density 660g/$\ell$, density 740 g/$\ell$인 통 옥수수 순으로 높았다. Flake의 가공정도를 증진시키면, 즉 3.8mm에서 2.8mm로 얇게 가공하면 전분 분해율이 유의하게 증가되었으며, 1.5mm로 더욱 얇게 가공하면 2.8mm 보다 증가하는 경향을 보였으나 유의적인 차이는 없었다(P<0.05). 12시간대에서 24시간대까지는 density가 낮은 통 옥수수가 높은 것보다 많이 분해되는 경향을 보였으나, 유의적인 차이가 없었고, 48시간대에서는 유의하게 높았다(P<0.05). 2) 단백질 분해율은 반추위내 배양시간이 경과함에 따라 모두 증가하는 경향이었다. 48시간대에서의 단백질 분해율은 분쇄 옥수수, 1.5 mm, 2.8mm, 3.8mm flake의 순으로 높았다(P<0.05). Flaking 처리시의 단백질 분해율은 분쇄 옥수수보다 유의하게 낮아졌으나, 8${\sim}$48시간대에서는 2.8mm, 1.5mm로 가공정도를 증진시킬수록 높아지는 경향이었다. 3) “a”값, 즉 물에 녹는 수용성 부분을 계산한 결과, 단백질의 “a”값은 flake가 분쇄 옥수수보다 유의하게 낮았다. 반면에 전분의 “a”값은 flake가 분쇄 옥수수보다 높았다. 곡류를 flaking 처리하면 전분이 젤라틴화 되어, 반추위 내에서 전분 분해속도는 증가되고, 단백질 분해속도는 감소되기 때문이라고 생각된다. 이와 같이 사료원료의 물리적 특성은 반추위내 배양시간별 영양소 이용율에 양향을 미친다. 그러므로, 반추가축 사료에 이용되는 원료들의 이와 같은 분해특성을 적절히 고려하면 단백질원과 탄수화물원의 반추위내 발효 동기화를 보다 최적화할 수 있을 것이다.