Crocker L M, DePeters E J, Fadel J G, Perez-Monti H, Taylor S J, Wyckoff J A, Zinn R A
Department of Animal Science, University of California, Davis 95616-8521, USA.
J Dairy Sci. 1998 Sep;81(9):2394-407. doi: 10.3168/jds.S0022-0302(98)70131-6.
Five primiparous Holstein cows (55 d in milk) that were fitted with ruminal and duodenal cannulas were used in a 4 x 5 incomplete Latin square to determine the effects of blends of steam-flaked and dry-rolled corn on site and extent of nutrient digestion and milk yield and composition. Diets were fed as total mixed rations and consisted of 45% forage and 55% concentrate; each diet contained 27% corn grain. Dietary treatments were composed of blends of dry-rolled and steam-flaked corn in ratios of 100:0, 67:33, 33:67, and 0:100. Intake of dry matter; digestibilities of dry matter, organic matter, acid detergent fiber, cellulose, neutral detergent fiber, fatty acids, and N; and microbial efficiency were unaffected by diet. Ruminal, postruminal, and total tract digestion of starch increased linearly, and starch passage to the duodenum decreased linearly, as the proportion of dry-rolled corn in the diet decreased. Ruminal propionate and valerate increased linearly, and acetate, butyrate, isovalerate, and the acetate to propionate ratio decreased linearly, as proportions of dry-rolled corn in the diet decreased; however, no changes in total volatile fatty acid concentrations in ruminal fluid were observed. Ruminal fluid pH was similar across diets. A decrease in dry-rolled corn decreased ruminal ammonia N and plasma urea N linearly. Milk yield and composition, as well as milk N fractions, were similar across diets. Although changes in fatty acid composition of milk fat were small, linear decreases in percentages of trans-C16:1 and cis-9- and cis-10-C18:1, as well as a linear increase in the percentage of C18:2 occurred as the proportion of dry-rolled corn in the diet decreased. An increased proportion of dry-rolled corn in the diet decreased digestion of starch in the rumen, and patterns of volatile fatty acid concentrations shifted accordingly. However, no effects on lactational parameters were observed.
选用5头装有瘤胃和十二指肠瘘管的初产荷斯坦奶牛（产奶55天），采用4×5不完全拉丁方设计，以确定蒸汽压片玉米和干碾压玉米混合比例对营养物质消化部位和程度、产奶量及奶成分的影响。日粮以全混合日粮形式投喂，由45%的粗饲料和55%的精饲料组成；每种日粮含27%的玉米籽粒。日粮处理由干碾压玉米和蒸汽压片玉米按100:0、67:33、33:67和0:100的比例混合而成。日粮对干物质采食量、干物质、有机物、酸性洗涤纤维、纤维素、中性洗涤纤维、脂肪酸和氮的消化率以及微生物效率均无影响。随着日粮中干碾压玉米比例的降低，瘤胃、瘤胃后和全消化道淀粉消化呈线性增加，淀粉进入十二指肠的量呈线性减少。随着日粮中干碾压玉米比例的降低，瘤胃丙酸和戊酸呈线性增加，乙酸、丁酸、异戊酸以及乙酸与丙酸的比例呈线性降低；然而，瘤胃液中总挥发性脂肪酸浓度未观察到变化。各日粮间瘤胃液pH值相似。干碾压玉米比例降低使瘤胃氨态氮和血浆尿素氮呈线性下降。各日粮间产奶量、奶成分以及奶氮组分相似。尽管乳脂肪脂肪酸组成变化较小，但随着日粮中干碾压玉米比例的降低，反式C16:1、顺式9-和顺式10-C18:1的百分比呈线性下降，C18:2的百分比呈线性增加。日粮中干碾压玉米比例增加会降低瘤胃中淀粉的消化，挥发性脂肪酸浓度模式也相应改变。然而，未观察到对泌乳参数的影响。
