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

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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.