Haisan J, Oba M
Department of Agricultural Food and Nutritional Science, University of Alberta, Edmonton T6G 2P5, Canada.
Department of Agricultural Food and Nutritional Science, University of Alberta, Edmonton T6G 2P5, Canada.
J Dairy Sci. 2020 Jul;103(7):6135-6144. doi: 10.3168/jds.2019-17698. Epub 2020 Apr 16.
The objective of this experiment was to determine the effect of pellet type and feeding amount on feeding behavior, dry matter intake, rumen fermentation, and milk production of lactating dairy cows. An experimental diet was formulated to provide an adequate amount of nutrients to a 650-kg cow producing 40 kg of milk per day, with a portion of the diet removed as a high-fiber (33.2% neutral detergent fiber; F) or high-starch (56.8% starch; S) pellet. Pellets were fed at a low (1 kg; L) or high (3 kg; H) amount twice per day alongside a partial mixed ration (PMR). Four complementary PMR were formulated for each pellet treatment such that the overall diet (pellet + PMR) offered to the cows was the same among all treatments. Eight ruminally cannulated cows were used in a 4 × 4 Latin square design with 14-d periods. Cows were fed PMR once daily at 1200 h, and pellet twice daily at 0600 and 1800 h. Data and samples were collected on d 11 to 14 of each period. By design there was a difference in pellet intake between the H and L treatments (5.31 vs. 1.81 kg/d), and PMR intake was reduced when H pellet was fed (22.9 vs. 25.3 kg/d); however, feeding H tended to increase total dry matter intake. Feed disappearance, which was measured as the amount of PMR consumed every 3 h following PMR delivery, was affected by the nutrient composition of the PMR as cows fed S (with high-fiber PMR) consumed 28.6% of their PMR intake within 3 h of delivery, whereas cows fed F (with high-starch PMR) consumed 33.5%. Duration that pH was below 5.8 tended to be lower when cows were fed the S pellet (270 vs. 125 min/d) compared with F. In addition, feeding the S pellet (with high-fiber PMR) decreased plasma concentrations of glucose (66.0 vs. 70.0 mg/dL) and insulin (1.90 vs. 2.25 ng/mL) compared with F. These results suggest that the composition of the PMR dictates rumen fermentation to a greater extent than composition of pellets. The S pellet was fed alongside a high-fiber PMR, which was more filling in the rumen, less fermentable, and contained more neutral detergent fiber. Although no difference was observed in milk production among treatments, the fact that feed intake pattern and rumen fermentation are better explained by nutrient composition of the PMR should be considered when formulating diets for lactating cows fed pellet and PMR, such as those milked with automated milking systems.
本实验的目的是确定颗粒料类型和饲喂量对泌乳奶牛采食行为、干物质采食量、瘤胃发酵及产奶量的影响。配制了一种实验日粮，为一头体重650千克、日产奶量40千克的奶牛提供充足的营养，日粮的一部分被替换为高纤维（中性洗涤纤维含量33.2%；F）或高淀粉（淀粉含量56.8%；S）颗粒料。颗粒料以低量（1千克；L）或高量（3千克；H）每天分两次与部分混合日粮（PMR）一起饲喂。针对每种颗粒料处理配制了四种互补的PMR，以使所有处理中提供给奶牛的总体日粮（颗粒料 + PMR）相同。八头安装了瘤胃瘘管的奶牛采用4×4拉丁方设计，每期14天。奶牛每天12:00饲喂一次PMR，每天06:00和18:00饲喂两次颗粒料。在每个周期的第11至14天收集数据和样本。按照设计，H组和L组的颗粒料采食量存在差异（分别为5.31千克/天和1.81千克/天），饲喂H组颗粒料时PMR采食量降低（分别为22.9千克/天和25.3千克/天）；然而，饲喂H组颗粒料倾向于增加总干物质采食量。饲料消失量通过在投喂PMR后每3小时消耗的PMR量来衡量，受PMR营养成分的影响，因为饲喂S组颗粒料（搭配高纤维PMR）的奶牛在投喂后3小时内消耗了其PMR采食量的28.6%，而饲喂F组颗粒料（搭配高淀粉PMR）的奶牛消耗了33.5%。与F组相比，饲喂S组颗粒料时pH低于5.8的持续时间倾向于更短（分别为270分钟/天和125分钟/天）。此外，与F组相比，饲喂S组颗粒料（搭配高纤维PMR）会降低血浆葡萄糖浓度（分别为66.0毫克/分升和70.0毫克/分升）和胰岛素浓度（分别为1.90纳克/毫升和2.2纳克/毫升）。这些结果表明，PMR的组成比颗粒料的组成对瘤胃发酵的影响更大。S组颗粒料与高纤维PMR一起饲喂，这种PMR在瘤胃中更易产生饱腹感，发酵性更低，且含有更多中性洗涤纤维。尽管各处理间产奶量未观察到差异，但在为饲喂颗粒料和PMR的泌乳奶牛（如采用自动挤奶系统挤奶的奶牛）配制日粮时，应考虑到PMR的营养成分能更好地解释采食量模式和瘤胃发酵这一事实。
