Do different levels of moderate feed deprivation in dairy cows affect feeding motivation?

Dairy cows grazed on pasture are likely to experience seasonal fluctuations in both the quantity and quality of forage available. In order to better understand how the variation in feed supply influences animal welfare, we need to understand the degree of hunger experienced during various levels of feed restriction. The aim of this study was to study feeding motivation in dairy cows by measuring cows' motivation to walk for food at different levels of feed deprivation. In the first study 18 lactating dairy cows were divided into three groups of six, with one group being tested each day, and each group tested four times, once every 3 days. Each cow was randomly allocated to one of four different levels of feed deprivation (0, 3, 6 or 9 h) and then given the opportunity to walk a number of consecutively increasing distances along a race in a U-turn to obtain a specified amount of food (increasing distance by 20 m starting at 20 m). All cows were randomly exposed to all feed deprivation levels over the 12 days in a crossover design. Maximal distance walked, milk production, body weight and body condition score (BCS) were monitored during the test period. The experiment was repeated with 12 non-lactating cows (divided into three groups of four) following the same protocol as in the first study. In the lactating cows, there was a significant effect of treatment on maximal distance walked with maximal distance increasing approximately linearly with increasing feeding deprivation levels. In both lactating and non-lactating cows, there was a significant effect of body weight on maximal distance walked with lighter cows walking greater distances. There was no significant relationship between BCS or daily milk production and maximal distance walked. The results show that feeding motivation in lactating dairy cows increases within a few hours of feed deprivation and that lighter cows may be more motivated to spend energy to obtain a limited amount of food compared to heavier cows. We conclude that this method is suitable for studying feeding motivation, at least in lactating dairy cattle. However, more research is needed to provide information about the levels of hunger at which an animal starts to suffer.