Behaviour and welfare of broiler breeders fed qualitatively restricted diets during rearing: Are there viable alternatives to quantitative restriction?

This study investigated whether feeding female broiler breeders on qualitatively, rather than quantitatively, restricted diets during rearing could improve their welfare while also achieving desired growth rates. There were six treatments, each with four replicate pens of 12 birds. From 1 to 20 weeks of age, birds in a control treatment (T1) received a quantitatively restricted amount of a standard mash diet while birds in five additional treatments (T2-T6) had ad libitum access to experimental diets. The latter were based on standard mash and contained supplements of calcium propionate (CaP, an appetite suppressant), or oat hulls (OH, a dietary diluent), or both, that were increased with bird age. Birds received diets with either increasing CaP (T2), low protein and increasing CaP (T3), OH and increasing Cap (T4), CaP and increasing OH (T5), or increasing both Cap and OH (T6). Effects of treatment on body weight, behaviour, response to a feeding motivation test, and blood indices of stress were recorded. Results showed that different qualitative restriction treatments can limit growth rate close to target. T4, with 40% OH and increasing CaP, limited body weight closest to the desired level. Between 6 and 20 weeks of age, control birds (T1) spent 47-54% of their time in object pecking, which was almost absent (< 1%) in all experimental treatment groups. Time spent inactive (sitting) and total time observed in all oral behaviours differed little between treatments. In a feeding motivation test, T1 birds consumed more food in 2 min after 2 or 4 h of food deprivation than did birds in any experimental treatment group. Treatment had no effect on the ratio of heterophils to lymphocytes or on the frequencies of other white blood cells. plasma corticosterone level was raised in T5 birds, whose mean body weight was suppressed to below the commercial target for most of the study, but was otherwise unaffected by treatment. The results suggest that appropriate appetite suppression, with or without dietary dilution, can be an effective method of controlling broiler breeder growth rate. However, although there was some indication that such dietary treatments may be beneficial for bird welfare (e.g. the absence of abnormal pecking at non-food objects), other behaviours and physiological indices of stress did not differ consistently between experimental and control birds. (c) 2005 Elsevier B.V. All rights reserved.