Gordon F J, Porter M G, Mayne C S, Unsworth E F, Kilpatrick D J
Agricultural Research Institute of Northern Ireland, Hillsborough.
J Dairy Res. 1995 Feb;62(1):15-27. doi: 10.1017/s002202990003363x.
Six lactating dairy cows were used in a three period, part balanced changeover design experiment to investigate the effects of forage digestibility and concentrate composition on the efficiency of nutrient utilization in lactating dairy cows. Six treatments comprising three forage regimens and two concentrate types (starch v. fibre) were examined in a 3 x 2 factorial design. The three forage regimens were high digestibility grass silage offered ad lib. (HA) or restricted to 6.5 kg dry matter/d (HR) and a low digestibility grass silage offered ad lib. (LA). Within each forage regimen animals were offered 10 kg/d of supplements containing either high-starch or high-fibre concentrations. Experimental periods lasted 28 d with a 10 d recording period, during which animal performance, ration digestibility and nitrogen and energy utilization were measured. Respiratory exchange measurements were made over a 72 h period using indirect open-circuit calorimetry. Throughout the experiment, there were no significant forage x concentrate interactions in any of the intake, production or nutrient utilization results. Milk yield was significantly influenced by forage regimen (24.1, 21.7 and 21.9 kg/d for HA, HR and LA respectively) and concentrate type (21.6 and 23.5 kg/d for high-starch and high-fibre respectively). Concentrate type also significantly influenced milk protein concentration (32.8 and 30.9 g/kg for high-starch and high-fibre respectively). Forage regimen significantly influenced the efficiency of utilization of metabolizable energy (ME) for milk production (k1) with values of 0.62, 0.64 and 0.59 for HA, HR and LA respectively. Concentrate type had no significant effect on ME intake, heat production or k1, although animals receiving the high-fibre concentrates synthesized proportionately 0.11 more milk energy per unit of available energy (ME intake--heat production) than those receiving the high-starch concentrates. Interpolation of the values obtained with the two high digestibility forage regimens indicated that at similar ME intakes there was a trend towards a higher k1 with the diet based on high digestibility silage, and this was in line with the higher metabolizability of the overall diet with this silage.
选用6头泌乳奶牛，采用三阶段部分平衡转换设计试验，研究饲草消化率和精料组成对泌乳奶牛养分利用效率的影响。采用3×2析因设计，考察了包括三种饲草方案和两种精料类型（淀粉型与纤维型）在内的六种处理。三种饲草方案分别为自由采食高消化率青贮牧草（HA）、限制采食至6.5千克干物质/天（HR）和自由采食低消化率青贮牧草（LA）。在每种饲草方案中，给动物提供每天10千克含高淀粉或高纤维浓度的补充料。试验期持续28天，其中有10天的记录期，在此期间测定动物生产性能、日粮消化率以及氮和能量利用情况。采用间接开路量热法在72小时内进行呼吸交换测量。在整个试验过程中，在任何采食、生产或养分利用结果中，饲草×精料交互作用均不显著。产奶量受饲草方案显著影响（HA、HR和LA分别为24.1、21.7和21.9千克/天）以及精料类型显著影响（高淀粉和高纤维分别为21.6和23.5千克/天）。精料类型也显著影响乳蛋白浓度（高淀粉和高纤维分别为32.8和30.9克/千克）。饲草方案显著影响用于产奶的代谢能（ME）利用效率（k1），HA、HR和LA的值分别为0.62、0.64和0.59。精料类型对ME摄入量、产热或k1无显著影响，尽管采食高纤维精料的动物每单位可利用能量（ME摄入量－产热）合成的乳能量比采食高淀粉精料的动物相应多0.11。对两种高消化率饲草方案所得值进行内插表明，在相似的ME摄入量下，以高消化率青贮饲料为基础的日粮有k1更高的趋势，这与该青贮饲料整体日粮的更高代谢率一致。
