As more and more dairy farmers move away from restricted feeding of pre-weaned calves and move towards feeding higher planes of nutrition for better health, growth, and long-term performance, it becomes important to learn more about the mechanism of voluntary intake regulation in young calves. The fact that their digestive tracts are still developing may interfere with the action necessary for satiety to take hold.1 While it has been shown that weaned calves exhibit a large variation in feed preferences,2 little research has been done into feed intake regulation in young calves provided both solid feed and milk components.
|Would growing calves choose only one type of food, if given the choice?
Or, would they choose a balanced diet?
In the research for their presentation and paper entitled "Determinants of feed preferences and intake in calves,"3 which was shared at the International Symposium on Energy and Protein Metabolism in Poland, in September, 2016, Berends et al. sought to gain insight into the long-term dietary preferences of
young calves, what determines those preferences, and if said preferences change over time. They also wanted to monitor the levels of intake when calves were offered all feed ad libitum. In other words, they wanted to find out what the calves preferred to eat and how much of it they would consume when consumption was unrestricted.
Materials & methods
For 25 weeks, starting at 17 days of age, 24 calves were given ad libitum access to milk replacer, water, long barley straw, long hay, chopped corn silage and pelleted starter concentrate. Intakes of each component for each calf were recorded for one full week, at both three and six months of age. Feed component energy and protein digestibility was assessed based on data in the literature. The importance of bulkiness was evaluated (and calculated) as a possible trigger for satiety. Table 1 shows the findings.
What the results mean
What the research team found was that despite a very large variation in the intake level of the individual diet components, the components calves did choose helped them all to achieve a remarkably constant digestible crude protein to digestible energy ratio. Indeed, when choosing for themselves, calves seem to self-regulate and select feeds that produce diets that stay balanced (unlike what we humans would do if given the choice)! Additionally, when provided unlimited access to both solid feed and milk components, calves do not wean on their own before six months of age.
Young calves truly seem to work to balance their own diets, even though they do so with a notable amount of variation in specific ingredients and feed types. This new information could lead to a variety of breakthroughs, including a new understanding of how to maximise the voluntary intake of pre-weaned calves and how to prevent growth dips at weaning.