RESPONSES OF 2 GENOTYPES OF CHICKEN TO THE DIETS AND STOCKING DENSITIES TYPICAL OF UK AND LABEL ROUGE PRODUCTION SYSTEMS .1. PERFORMANCE, BEHAVIOR AND CARCASS COMPOSITION
Pd. Lewis et al., RESPONSES OF 2 GENOTYPES OF CHICKEN TO THE DIETS AND STOCKING DENSITIES TYPICAL OF UK AND LABEL ROUGE PRODUCTION SYSTEMS .1. PERFORMANCE, BEHAVIOR AND CARCASS COMPOSITION, Meat science, 45(4), 1997, pp. 501-516
'Label Rouge' (LR) chickens are reputed to possess improved sensory ch
aracteristics compared with birds reared under intensive conditions. T
he effects on body weight, food utilisation, behaviour and carcass com
position, of genotype (Ross I vs ISA '657'), diet (conventional UK bro
iler vs LR) and stocking density (17.0 birds m(-2) vs 4.25 birds m(-2)
) were evaluated in a 2 x 2 x 2 experiment. ISA birds were grown to 83
days, and compared with Ross birds grown to 48 days; additionally ad
libitum and control-fed Ross birds were grown to 83 days. Performance
and behaviour parameters were assessed empirically. The effects on car
cass composition were evaluated using standardised carcass dissection
techniques and analysed by analysis of variance. ISA birds grown under
LR conditions to 83 days had similar body weights to Ross birds grown
under UK broiler conditions to 48 days, but LR birds consumed more fo
od, and converted food into meat less efficiently. LR birds had no mor
tality, whilst UK broiler mortality was 11.3%. Under similar condition
s, Ross birds had a faster body weight gain, a larger food intake, but
more efficient food conversion ratio and higher incidence of mortalit
y. Birds stocked 17.0 m(-2) had lower body weights, consumed less food
and, when fed UK diets, converted food less efficiently than birds st
ocked 4.25 m(-2). Both genotypes had a faster growth rate on UK diets,
similar food intakes, and, as a result, better food conversion than b
irds given LR diets. LR and UK broiler birds had similar carcass compo
nent weights, breast meat yields, and total meat yield, but LR birds h
ad less meat on the frame, larger drumsticks and more meat on the wing
s. Under similar conditions, ISA birds had a larger percentage of wing
and total bone, but a smaller percentage of breast meat and total mea
t yields. When Ross birds had controlled growth, total meat, bone and
skin yields were similar to those of ISA birds. Birds stocked 4.25 m(-
2) had more breast meat and larger frames than, but similar meat, bone
and skin yields to, birds stocked 17.0 m(-2). Most carcass components
were heavier in birds fed UK broiler diets, but, on a percentage basi
s, these birds had larger thighs, but smaller drumsticks. (C) 1997 Els
evier Science Ltd.