Detection and comparison of time patterns of behaviours of two broiler breeder genotypes fed ad libitum and two levels of feed restriction

Abstract

Time structure of behavioural patterns of broiler breeders were investigated to assess comparative behavioural complexity using “Theme”. The behaviour of an experimental dwarf heavy broiler breeder selected for better viability and reproductive traits at the partial expenses of growth (E) was compared to a standard heavy broiler breeder (S). Both were either fed ad libitum (A), feed restricted at 55% of A from 6 to 15 weeks of age (I), or feed restricted as in commercial practice to match a standard growth curve (R) in a 2 genotypes × 3 diets factorial design with 8 pens of 14 hens per treatment. The fine mash feed contained 10 MJ ME/kg. In each pen, three hens were coloured-marked and video recorded twice from 6 to 13 weeks. Four to 5 h after feed distribution, 10 min files (288) were coded by focal sampling and 1 min files (107) of one hen per pen were coded in detail in the morning and afternoon sessions. In the 10 mins files, while E rested more often and longer on average than S, the total number of changes of states recorded per hour were 222 for E versus 184 for S. When both genotypes were feed restricted, resting was replaced by more frequent stepping and standing bouts, and eating events by pecking at the empty feeder and at the litter. The overall number of time structured T-patterns detected by Theme were more frequent per hour of behaviour in genotype E (142) compared to S (115) and in the feed restricted hens (151) compared to the ad libitum fed hens (83). Genotype and diet modulation of activity followed different paths and interactions were not significant. In the 1 min detailed files, most of the pecks were included in T-patterns and their mean lengths were consistent (feed = 145 ms for E and 161 ms for S; litter = 174 ms; empty feeder = 193 ms) whatever the feed restriction levels. Feed restriction did not “disorganize” the behaviour of broiler breeder hens and “hyperactivity” of feed restricted hens was mainly due to transitions between various activities. A transfer of feeding activities toward foraging and spot-pecking and a reduction of the number and duration of resting bouts were the major observed changes. No specific sequences of behaviour attributable to feed restriction could be consistently identified. A more detailed analysis of resting in heavy genotypes might bring new insights on adaptability of broiler breeders to ad libitum feeding.