Early locomotor behaviour in genetic stocks of chickens with different growth rates

Reduction in exercise increases the occurrence of lameness in meat-type chi ckens. Locomotor activity is dramatically reduced during the finishing peri od in chickens from fast-growing genetic types compared to slow-growing gen etic types, but it is not known whether this difference is already present during the starting period and may be influenced by genetic factors. In ord er to define the effect of genetic origin on early locomotor behaviour, exe rcise was compared from 1 to 22 days of age in two meat-type chicken stocks differing in growth rate: male broilers (B) which grow fast and are often lame, and male "label rouge" chickens (L) which grow slowly and are rarely lame. Time budget (lying, standing, drinking, eating, walking) was measured by sc anning in six repetitions of five birds (density = 2.5 birds/m(2)) at 1, 8, 15 and 17 days of age. Standing bouts were analysed by focal sampling at 2 -3, 6-7, 13-14 and 20-21 days of age. B chicks spent less time standing than L chicks at 15 days of age (B = 13 /- 2%, L = 24 +/- 1%, P < 0.01) and 17 days of age, and spent more time lyi ng at 17 days of age (B = 73 +/- 3%, L = 60 +/- 4%, P < 0.05). The major part (74%) of the total active time observed by focal sampling wa s linked to feeding activity. At 2 and 3 days, the activity of B chicks was half that of L chicks during standing bouts (duration of walking per bout: 19 +/- 4 s for B; 45 +/- 4 s for L, P < 0.05). The activity observed by fo cal sampling during non-feeding bouts at 20-21 days was significantly corre lated with the corresponding data recorded at 2-3 days in the same chicks i n the B stock but not in the L stock. We concluded that (1) both B and L genetic stocks have the same overall act ivity during the first 3 days of age (scanning) but they exhibit different organisation and composition of standing bouts (focal sampling). (2) Geneti c factors are probably involved in the expression of locomotor behaviour in very young chicks. (3) The correlations between the levels of activity at early and later ages suggest that selection of young mobile broiler chicks might increase activity at a later age and might therefore reduce the occur rence of leg abnormalities. (C) 2000 Elsevier Science B.V. All rights reser ved.