The motivation of high- and low-yielding dairy cows to obtain supplementary concentrate feed

Abstract

The higher nutrient requirements of lactating dairy cows may cause hunger, and therefore the motivation to consume feed, to increase with milk yield. An experiment was conducted that aimed to establish whether dairy cows could be trained to obtain a food reward in response to lever pressing and, if so, whether high-yielding dairy cows had a greater hunger than low-yielding cows. As a measure of hunger the demand to consume feed was evaluated. In total, 7 high- and 6 low-yielding dairy cows were trained in 2 groups to use a lever to obtain 0.33 kg concentrate rewards. For at least a 9-day period each cow was tested for 30 min/day by increasing the number of lever presses required to receive each additional reward in a progressive ratio of 3. After the test cows were allowed to return to their quarters, where they could consume a total mixed ration (TMR). Initially high-yielding cows had lower maximum number of lever presses than low-yielding cows, possibly so that they could consume TMR after finishing the test, but from Days 6–9 the number for high-yielding cows increased until it was the same as low-yielding cows. There was a positive correlation between the maximum lever presses by high-yielding cows and their time in the test pen, which was not evident for low-yielding cows. The high-yielding cows spent more time feeding on the TMR after the test than low-yielding cows. Therefore, although the high-yielding cows were not prepared to work harder for food rewards, they did seem to adopt a more efficient feeding strategy by only spending time in the test pen if they were still receiving rewards and minimizing time without feed by eating more post-test.