Welfare assessment of broiler breeders that are food restricted after peak rate of lay

Abstract

1. Broiler breeder females were reared on one of three growth curves (ad libitum, conventional or modified restriction) and given rations containing a high or low concentration of crude protein. After the peak rate of lay they were fed ad libitum or a decreasing quantity of food in response to declining egg production. The welfare of the birds was assessed by determining the changes in indices of welfare at 36, 48 and 60 weeks of age. 2. Body weight increased rapidly in restricted birds fed ad libitum post-peak and water intake declined. 3. Post-peak food restriction was associated with a decrease in resting and increased drinking and spot-pecking activities. Birds that were food restricted during rearing spent more time foraging and spot-pecking at 36 and 48 but not 60 weeks of age. 4. Immune function increased with age but was not affected by the experimental treatments. The heterophil-lymphocyte ratio in birds fed ad libitum during rearing was numerically lower at 36 and higher at 48 and 60 weeks of age compared with restricted birds. 5. There was no effect of treatment on plasma corticosterone concentration. Creatine kinase activity was high at 60 weeks in treatments that were characterised by poor reproductive status and the activities of other enzymes reflected differences in reproductive status and mortality. 6. There was no long-term welfare or production advantage from feeding low protein rations or more generous feeding during the rearing period compared with conventional food restriction programmes.

Scientific Opinion on the influence of genetic parameters on the welfare and the resistance to stress of commercial broilers

“…Broiler breeders fed ad libitum have characteristically low rates of lay, poor persistency and produce a large proportion of eggs with defective egg shells that cannot be used for incubation (Renema and Robinson, 2004). For example, in the study of Hocking et al (2002) birds fed ad libitum produced only 28 chicks to 60 weeks of age (restricted birds produced 134). This improvement in egg laying and the substantial reduction of mortality are the main reasons for feed restricting broiler breeders (EFSA Panel on Animal Health and Welfare, 2010).…”

Identification of novel candidate genes for follicle selection in the broiler breeder ovary

“…Feed restriction does however reduce follicle numbers in the ovarian hierarchy to a normal level [5], and consequently decreases the chance of multiple ovulation. Despite the benefits to the health of the birds, the degree of hunger experienced by the birds has raised concerns in some quarters as to the resulting impact on the birds’ welfare [3,6,7]. …”

RETRACTED ARTICLE: Immunosuppressive interactions of viral diseases in poultry

“…Assays to assess immune-competency are mainly used, however, a broader approach could assess combined environmental and infectious contributions of immunosuppression (Dietert et al, 1994;Haq et al, 2013). The heterophil:lymphocyte ratio in the circulating blood is a general indicator of stress and may provide general assessment of immunocompetency (Hocking et al, 2002).…”