Effect of group size on performance, bone strength and skin lesions of meat rabbits housed under commercial conditions
Research was conducted to investigate the effect of group size (6, 12, 18, 30, 42 and 54 animals) on performance, bone strength and skin lesions of meat rabbits housed in cages at a density of 17 animals/m2 The research was performed in three succeeding experiments (A, B and C) from March 1995 until July 1996 in a compartment with 16 cages. Weaned rabbits of 31 days of age were placed. Body weight, feed intake and mortality were recorded until 73 days of age. At start and the end of each trial the animals were weighed individually to determine uniformity per cage. In the second and third experiment the trial period was prolonged until 80 days of age to investigate the effect of group size on aggressiveness by scoring skin injuries. At the end of the second and third experiment bone strength was determined. No influence of group size on growth, feed intake and mortality was observed. At 73 days the animals had gained an average live weight of 2462 g at a daily growth of 40.5 g and a daily feed intake of 122.7 g. There was a tendency (p<0.1) for a better feed efficiency of 6 animals/cage (3.02) compared to 12, 30 and 54 animals/cage (resp. 3.11, 3.07 and 3.12). No effect of group size on uniformity and bone strength was found. The percentage of injured animals was not related with group size, but the severity of the injuries increased with age. At 73 days of age 5.7%, 16.4% and 12.6% of the total number of animals in experiment A, B and C had skin injuries, with more than 80% of the injuries located at head and ears. At 80 days of age 42.5% and 20.1 % of the total number of animals in resp. experiment B and C were scored with injuries, 50% of which were observed at the genitals. The results of this research show that at a density of 17 animals/m2 floor, space use efficiency can be improved by increasing group size, without altering performances. Our findings support the recommendation to finish the fattening period before 80 days of age.
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