摘要
The objectives of this study were to determine if feed sorting differs between primiparous (PP) and multiparous (MP) cows, if sorting changes from the period of peak lactation to peak dry matter intake (DMI), and whether feed sorting affects efficiency of production. Data on DMI, milk production, feed sorting (particle size of offered and refused feed), and energy status (plasma nonesterified fatty acid, β-hydroxybutyrate, insulin and glucose concentration) were collected on 30 PP and 30 MP lactating Holstein dairy cows, individually housed and fed in tie-stalls, during 3 wk (wk 2, 6, and 10) over 10 wk of a lactation study. Cows averaged 53, 81, and 109 ± 10 d in milk (DIM) at the beginning of each of the 3 recording weeks. To determine sorting, feed samples were separated with a particle separator that had 3 screens (19, 8, and 1.18 mm) and a bottom pan, resulting in 4 fractions (long, medium, short, fine). Over the study period, MP cows consumed more DM and produced more milk than did the PP cows, but had similar efficiency of production (kg of milk/kg of DMI), and similar levels of plasma indicators of energy status. Across the study period, DMI increased, whereas milk yield decreased, resulting in decreased efficiency of milk production as cows moved further into lactation. All cows had higher nonesterified fatty acid and lower insulin concentrations in plasma at 53 DIM compared with at 81 and 109 DIM, suggesting they were mobilizing more body fat at that earlier stage of lactation. Across periods, all cows sorted against the longest ration particles, did not sort the medium ration particles, and sorted for fine ration particles; as a result, all cows consumed less neutral detergent fiber (NDF) and physically effective NDF (proportion of NDF retained on the 19- and 8-mm screens of the particle separator) than predicted. Greater selection against the longest ration particles was associated with greater efficiency of milk production; however, this sorting pattern also tended to be associated with lower milk fat percentage. The extent of the observed sorting against the longest, physically effective ration particles and for the finest ration particles was greater for PP cows than for MP cows across all 3 observation periods. Feed sorting remained consistent in cows across the DIM evaluated in this study and that this sorting behavior can affect the efficiency of milk production as well as milk fat percentage. Further, PP cows engage in more sorting of their ration than MP cows.
摘要译文
这项研究的目的是确定是否初产（PP）和多子（MP）的奶牛饲料之间的排序不同，如果从峰值泌乳期排序改变到峰值干物质摄取量（DMI）和进料分选是否影响生产效率。对DMI数据，产奶量，饲料排序（所提供粒度和拒绝饲料），以及能源的状态（非酯化血浆脂肪酸，胰岛素和葡萄糖浓度）上收集30 PP和30的MP泌乳荷斯坦奶牛，单独圈养并供给在提携档，在3周（周2,6和哺乳期研究10）超过10周。母牛平均53，81，和109±10天的牛奶（DIM）在每个记录3周的开始。为了确定排序，饲料样品进行分离用的颗粒分离器，其具有3个屏幕（19，图8，1.18毫米）和一个底盘，导致4级分（长，中，短，细）。在研究期间，MP消耗的奶牛更DM并生产更多的牛奶比没有的PP奶牛，但有生产类似的效率（公斤牛奶/公斤的DMI），以及能源状况等离子指标相似的水平。横跨研究期间，DMI增加，而乳产量减少，导致牛奶生产效率下降牛进一步移入泌乳。所有牛具有较高的非酯化脂肪酸和下胰岛素浓度在血浆中在53 DIM具有在81和109 DIM相比，这表明他们是在哺乳期的早期阶段，动员更多的脂肪。跨越时间，所有的牛进行排序对最长口粮颗粒介质口粮颗粒没有排序，整理细颗粒的口粮;其结果，所有奶牛消耗更少的中性洗涤纤维（NDF）和物理有效NDF（NDF比例保持在19-和8毫米屏幕颗粒分离），比预测。针对最长的口粮颗粒较大的选择是牛奶生产的效率有关;然而，这种分类模式也趋于更低乳脂率相关。针对最长观察到的分拣的程度，实际有效配给颗粒和最好的口粮颗粒是更大的PP牛比MP奶牛在所有3观测时段。进料分拣留在奶牛横跨在这项研究中，并且这个排序行为可能会影响牛奶的生产效率以及乳脂率评价在DIM一致。而且，PP奶牛搞自己的口粮比MP奶牛更多的排序。
T.J. DeVries[*]; L. Holtshausen[†]; M. Oba[‡]; K.A. Beauchemin[†]. Effect of parity and stage of lactation on feed sorting behavior of lactating dairy cows[J]. Journal of Dairy Science, 2011,94(8): 4039–4045