More solid feed or ad libitum long straw? Best diet to improve veal calf welfare

Veal calf diets provide insufficient rumination opportunities as indicated by abnormal oral behaviour development in these calves; i.e. tongue playing/rolling and excessive oral manipulation of environment. We investigated whether veal calves would benefit more from increased amounts of a solid feed mixture or unlimited availability of long straw. HolsteinFriesian bull calves (n=60) received milk replacer and solid feed (80% concentrate, 10% corn silage, and 10% chopped straw, DM basis) up to 27 wk of age. Control calves (CO) and calves with unlimited straw (ST) received 115 kg solid feed (based on Dutch veal). Calves with increased solid feed (SF) received 300 kg (based on intake of calves fed ad libitum). Milk replacer was adjusted for equal growth. ST calves received unlimited long barley straw in racks. Behaviour was monitored at 15 and 24 wk of age using instantaneous scan sampling every 2 hours from 06:30 to 20:30 h at a 6 min interval. Data were analysed with a generalised linear mixed model. ST calves used the straw rack 2.3±1.0 and 8.6±1.8% of total scans at 15 and 24 wk. ST calves displayed less abnormal oral behaviours than CO and SF calves (ST: 4.4±0.8, CO: 10.0±1.1, SF: 8.6±0.8; P=0.004). ST calves ruminated more than CO calves at 15 wk (ST: 13.0±0.9, CO: 8.6±1.0, SF: 10.3±1.4), and than CO and SF calves at 24 wk of age (ST: 16.5±2.0, CO: 6.0±0.7, SF: 8.3±1.1; P=0.043). No differences in tongue playing and lying levels were observed. Calves played more at 15 compared with 24 wk (15 wk: 1.8±0.3, 24 wk: 0.6±0.1; P=0.008), irrespective of treatment. This study suggests that unlimited straw has the potential to improve calf welfare more than increased amounts of solid feed, potentially because the straw offered unlimited chewing opportunity with no great impact on nutritional status.