Taste Aversion as a Motivation Test of Hunger in Dairy Calves

Megan Woodrum Setser^1,2Joao HC Costa¹Katherine Creutzinger^1,2*Daniel Brown²

• ¹University of Vermont, Burlington, United States
• ²University of Wisconsin–River Falls, River Falls, Wisconsin, United States

The objectives of this study were to investigate a new method to assess dairy calf hunger. These experiments aimed to determine if 1) calf consumption of milk changed when a bitter substance was added and 2) the addition of a bitter substance to milk could be used to assess hunger in pre-weaned dairy calves. Twenty-seven individually housed calves (17 Holstein, 10 dairy-beef terminal crosses; 21 ± 3 d of age) were enrolled in 2 Latin Square Design experiments. For each experiment, calves were assigned to two treatments: 1) bitter (milk with quinine) and 2) control (unaltered milk). In Experiment 1, calves received milk with 0.0, 0.2, 0.3, and 0.4 g/L quinine at their afternoon feeding. In Experiment 2, both control and bitter treatments (0.0 vs. 0.35 g/L quinine) experienced different intervals between meals (6, 12, and 16 h). Milk and grain intake and feeding behaviors were recorded for both experiments. Calves in Experiment 1 consumed less milk and performed more non-drinking oral behaviors when it was altered with quinine at 0.4 g/L compared to all other concentrations. Calves also performed more aversive behaviors when fed milk with any quinine concentration compared to 0.0 g/L. The reduced milk consumption and performance of more aversive behaviors during the consumption of bitter milk indicates that calves find quinine aversive. In Experiment 2, calves in the bitter treatment consumed less milk than control calves regardless of the length of time between meals. No interaction between treatment and feed withhold time was observed on milk intake, indicating calves did not change their willingness to consume bitter milk when feed was withheld for a longer time. However, calves provided unaltered milk performed more drinking bouts when milk was withheld longer, and all calves performed more non-drinking oral behaviors at 12 and 16 h and consumed more starter after longer periods between meals, indicating greater hunger. Overall, these results show that calves altered their consumption of bitter milk when the concentration was greater, and that intake should not be the sole measure to consider when utilizing taste aversion to assess calf hunger.