Impact of forage inclusion rate on the occurrence and persistence of feed sorting behaviour in growing dairy cattle

一种新的生长奶牛喂养方案，将切碎的秸秆和多种质地的犊牛精料混合在干混合日粮（TMR）中，旨在提供一致的谷物和饲料摄入量，包括刺激瘤胃的良好磨粒纤维来源，以及足够的精料摄入量以提供所需的营养物质。这种喂养方案的关键特点之一是保持饲料和谷物在配方量上的一致摄入量。日粮的膳食选择（分类）有可能导致营养摄入的不平衡。因此，本研究的目的是确定饲料添加水平对饲喂干TMR方案的乳牛分选行为和生长的影响。第二个目标是确定在小牛转换到传统的口粮后，发达的喂养模式如何延续。我们假设，增加饲料包涵水平将增加谷物的分选量，从而增加营养消耗的变异性。我们还假设，在小牛过渡到传统的口粮后，这种行为会延续下去。为了验证这些假设，10头从出生到12周龄的荷斯坦小牛将被分配两种处理中的一种：1)85%浓缩物和15%切碎（2.5厘米）稻草，持续12周；或2)85%浓缩物和15%切碎的稻草连续6周，然后70%浓缩物和30%切碎的稻草连续6周。在24周龄时，所有动物将过渡到含有50%玉米青贮和50%干草的常规日粮，为期3周。采食量、行为（分拣、进食、躺卧和反刍）、生长和健康将在整个研究过程中进行监测。这项研究不仅将为Nutreco Canada Agresearch提供该喂养计划的经验支持，而且还将补充圭尔夫大学（University of Guelph）在创造奶牛喂养行为发展基础知识方面的研究。这项研究的主要受益者是加拿大乳制品生产商，他们实施了这项喂养计划，以降低饲料成本，提高替代奶牛的健康、效率和福利。

A new feeding program for growing dairy cattle, which incorporates chopped straw and a multi-textured calf concentrate in a dry total mixed ration (TMR), has been developed with the intent of providing consistent intakes of grain and forage, including a good source of abrasive fibre for rumen stimulation, and sufficient intake of concentrate to provide nutrients required. One of the key features of this feeding program is to maintain a consistent intake of both forage and grain in the formulated amounts. Dietary selection (sorting) of the ration has the potential to cause imbalances in nutrient intakes. Thus, the objective of this research is to determine the impact of forage inclusion level on the sorting behaviour and growth of young dairy cattle fed this dry TMR program. A secondary objective is to determine how developed feeding patterns carry over after the calves are switched to a conventional ration. We hypothesize that increasing the forage inclusion level will increase the amount of sorting for grain, thus increasing variability in nutrients consumed. We also hypothesize that this behaviour will carry over after calves are transitioned to a conventional ration. To test these hypotheses, 10 Holstein calves, raised similarly from birth to 12 weeks of age, will be assigned 1 of 2 treatments: 1) 85% concentrate and 15% chopped (2.5 cm) straw for 12 weeks; or 2) 85% concentrate and 15% chopped straw for 6 weeks, then 70% concentrate and 30% chopped straw for 6 weeks. At 24 weeks of age, all animals will be transitioned to a conventional ration, containing 50% corn silage and 50% haylage, for a 3-week period. Feed intake, behaviour (sorting, feeding, lying, and ruminating), growth, and health will be monitored throughout the study. This research will not only provide Nutreco Canada Agresearch empirical support for this feeding program, but also complement research at the University of Guelph in creating fundamental knowledge on the development of feeding behaviour in dairy cattle. The primary beneficiaries of this research are the Canadian dairy producers who implement this feeding program to reduce feed costs, and improve the health, efficiency, and welfare of their replacement dairy cattle.