Optimal group size for calves fed in transponder-controlled milk feeders

Sammanfattning: Traditionally preweaned calves have been kept in single pens until the time for weaning. However, nowadays the general opinion from both the society and manufactures is that calves should preferable be kept in groups (DeLaval, 2000). There are several reasons why group housing is increasing. This system for rearing calves has many advantages compared with single housing. Group housing give calves opportunity to perform social behaviours (Jensen et al. 1998, Jensen, 2004) and stimulates the consumption of forage and grain (Phillips, 2004, Babu et al. 2004). The aim of this project was to achieve knowledge about the optimal group size for group housed calves that are fed milk from automatic milk feeders. The project has been conducted in collaboration with Delaval. Recent literature was reviewed and an interview part was conducted where 7 different farms in the Netherlands, Norway and Latvia was visited. The interviews showed that most farmers were satisfied with their milk feeder and their group housing system. Group housing is more preferable compared to single housing in several aspects. This housing system makes the calves develop a social behaviour which has a positive impact on the ability to function in a group even later in life. The literature study and the interviews also showed that the optimal group size is very much depending on the management system and the presumptions on the actual farm. However, the incidence of disease outbreaks can be greatly reduced and the daily weight gain can be increased if stable groups are kept. This study concludes that calves should preferable be kept in small groups (max 12 individuals) and the age range among them should be as small as possible in order to achieve optimal conditions for the calves.