Abstract #M31

# M31
Effects of different number of animals relative to a single feeding space on performance and behavior in Holstein bulls fed high-concentrate diets.
Maria Devant*1, Alex Bach2,1, Marçal Verdú1, 1IRTA-Ruminant Production, Animal Nutrition, Management, and Welfare Research Group, Caldes Montbui, Spain, 2ICREA, Barcelona, Spain.

One hundred and eight Holstein bulls (155 ± 2.0 kg BW and 121 ± 0.8 d age) were randomly allocated to one of 6 pens and assigned either in groups of 16 (Ratio16) or in groups of 20 (Ratio20) to a single space feeder with lateral protections. Each pen (6 m × 12 m) had also 1 straw feeder, and 1 drinker. Concentrate intake was recorded daily, straw consumption weekly, and BW fortnightly (total 15 periods). Animal behavior was registered every 28 d by scan sampling. Animals were slaughtered after 219 d and HCW and carcass quality recorded. Data were analyzed using a mixed-effects model with repeated measures. Mean concentrate intake (6.77 ± 0.168 kg/d), concentrate efficiency (0.22 ± 0.016 kg/kg), and carcass weight (271 ± 2.2 kg) were not affected by treatments. An interaction between treatment and time was observed in most of eating behavior parameters. During the growing (period 1 to 11) in Ratio16 bulls the number of visits to the feeder tended (P = 0.08) to increase, total daily time devoted to eat was greater (P = 0.01), whereas meal size (P = 0.05), meal duration (P = 0.001), and eating rate (period 5 to 11; P = 0.001) were lesser compared with Ratio20 bulls. However, at the end of the fattening period (periods 12 to 15) no differences between treatments were observed. In Ratio16, the percentage of animals drinking was greater (P = 0.05) compared with Ratio20. Moreover, an interaction between treatment and time was observed in the percentage of animals performing self-grooming (P < 0.05) and attempting to mount (P = 0.10). In conclusion, when the ratio of number of animals to a single feeder was reduced by 20%, the number of visits tended to increase, animals had shorter meals and meal sizes, and eating rate decreased; however, these differences were only observed during the growing period. These data may suggest that feeding space to animal ratio has an effect on eating behavior during the growing period, where social facilitation may be important. However, at the finishing as eating behavior becomes more individualized and/or animals learn to take turns, the feeding space to animal ratio is less critical.

Key Words: bulls, feeding space to animal ratio, eating behavior