Behavioural effects of feed dilution and daily roughage provision in male Hubbard M77 broiler breeders during rearing

Abstract

A growing public interest in broiler chicken welfare is leading to an increase in the number of private companies committing to switch to slower growing hybrids, particularly those approved by schemes such as the Better Chicken Commitment. These slow growing chickens are often, however, a result of cross breeding a slow growing hybrid with a conventional hybrid. The Hubbard JA787 for example, is fathered by the M77 which has a conventional growth rate. As such, these broiler breeder males still experience feed restriction as is routine with other conventional hybrids. This study, therefore, aimed at investigating the effects of a combination of qualitative feeding restriction strategies (i.e. feed dilution and daily roughage) on several behavioural indicators of welfare in Hubbard M77 broiler breeder cockerels during the rearing period. Two hundred M77 broiler breeder cockerels were housed from 5 to 10 weeks of age in 12 pens (6 pens/treatment). The treatments were conventional feed restriction (Control) and feed with 20 % dilution with oat hulls and a daily provision per pen of 150 g of alfalfa roughage (D+R). In the home pen, novel object (NO) tests and frustration assessments during thwarted feeding were conducted, with responses captured on video. Additionally, four birds from each pen underwent a tonic immobility (TI) test. These behavioural tests were carried out weekly at 6, 8, and 10 weeks of age. After euthanasia, two feathers from each bird were plucked and examined macroscopically for fault bars. The results from the NO test introduced doubt as to whether the D+R diet reduced hunger in the short term (4 hours) or increased it in the longer term (24 hours). In the frustration test, control birds performed more behavioural transitions and spent more time pacing and pecking the feed box than D+R birds (P < 0.05), but these results were not consistent across weeks of age. Finally, no diet treatment differences were observed in the tonic immobility test or in the assessment of feather fault bars. We conclude that a combination of feed dilution with 20 % oat hulls and daily provision of roughage did not significantly improve M77 broiler breeder cockerel welfare during rearing according to the indicators assessed. Furthermore, the present study contributes to the growing literature suggesting that qualitative feed restriction, while promising in theory, in practice fails to deliver strong and consistent improvements to animal welfare.