Resting and social behaviour of dairy heifers housed in slatted floor pens with different sized bedded lying areas

Abstract

The hypothesis that an increase in the straw bedded resting area for group housed heifers would increase synchronization of resting behaviour and decrease aggressive and abnormal behaviour was tested. An experiment was conducted on two Danish commercial dairy farms with 20 Danish Friesian heifers (approximately 400 kg) from November 1994 to April 1995. The experimental pens were constructed on existing slatted floor and contained a total area of 27 m 2 per pen with five heifers in each pen. Three different sizes of lying area (1.8, 2.7 and 3.6 m 2 per heifer) bedded with straw were established in each pen for three consecutive periods of 5 weeks. Resting and social behaviour were recorded using direct observations for 24 h at the end of each 5 week treatment period. The synchronization of resting behaviour was reduced ( P = 0.002) when the heifers were offered 1.8 m 2 bedded lying area per heifer compared with 2.7 or 3.6 m 2 per heifer, and the heifers were more aggressive, as more butting ( P = 0.007) and forcing another heifer to stand up ( P = 0.02) were seen. The frequency of leaning against other heifers was highest ( P = 0.05) at the lowest space allowance in the bedded area. The results indicate that increasing the resting area from 1.8 m 2 to 2.7 or 3.6 m 2 per heifer improved the welfare of group housed dairy heifers.