Effect of portion size and milk flow on the use of a milk feeder and the development of cross-sucking in dairy calves

This study aimed to investigate whether reducing the milk flow and increasing the milk portion size of a computer-controlled milk feeder would lead to less cross-sucking and fewer unrewarded feeder visits in dairy calves. Five groups, each with 9 or 10 calves (n = 48), were housed in pens with one milk feeder in each pen, and exposed to four milk-feeding treatments in a cross-over design with four periods of 1 week. All four treatments involved a daily allowance of 8 L of whole milk, with variation in the maximum portion size and the rate at which milk entered the teat of the milk feeder. The treatments were: 1) 1 L/Low flow (1 l portions at a flow of 300 ml/min); 2) 2 l/Low flow (2 l portions at a flow of 300 ml/min); 3) 1 l/High flow (1 l portions at a flow of 600 ml/min); 4) 2 l/High flow (2 l portions at a flow of 600 ml/min). When the calves were fed milk in 2 l portions, they had fewer rewarded visits (P < 0.001) than when they were fed 1 l portions. When the calves were fed the milk in 2 l portions with a low flow, they spent more time on rewarded visits during which they did not ingest the whole portion (P < 0.05) and had more (P < 0.001) and longer (P < 0.001) rewarded visits during which they ingested less than 0.5 l of the portion. The treatments had no effect on the occurrence of cross-sucking. A higher number of bull calves were subject to cross-sucking than heifer calves (P < 0.001), and in total they also received more cross-sucking events than heifer calves (P < 0.001). Heifer calves initiated a higher frequency of cross-sucking than bull calves (P < 0.001). We concluded that when calves are given milk in 2 l portions, a very low flow should be avoided, as this may reduce the calves' milk intake. The finding that bull calves were subject to cross-sucking more often than heifers, while heifer calves initiated more cross-sucking than bulls warrants further studies on these gender effects.