Faster growing birds ate larger meals, but fewer per day, than slower growing birds
Take Home Message: Feeding behaviour indicates that birds selected for growth are not ‘constantly hungry’ and their welfare therefore not compromised.
The structure of short-term feeding behaviour that results from intensive genetic selection for growth is similar to that observed in many other species. This finding dispels the hypothesis that intensive selection for growth leads to birds that are constantly hungry.
“We found no alteration of the overall organisation of short-term feeding behaviour into bouts in relation to selection intensity,” the Scottish Agricultural College’s Jennifer Howie told delegates at the British Society of Animal Science’s annual conference.
Selection for increased growth rate in livestock may be accompanied by increases in requirements for energy and nutrients. It has been suggested that intensively selected broilers have altered food intake control mechanisms and could be constantly hungry, due to their high resource demands. “If this were true it would be a major welfare issue,” said Miss Howie.
“And as a ‘side-effect’ of genetic selection it would also lead to changes in the feeding behaviour of birds, such as the clustering of visits into meals and the probability of birds starting a new meal in relation to the time since the last meal.
“So the aim of this study was to test whether broilers intensively selected for growth showed any alteration in the structure of their feeding behaviour that would indicate a change in the underlying hunger and satiety control mechanisms,” she added, explaining the rationale behind her team’s work.
Data of visits to feeders from 16,823 broilers aged between two and five weeks from four genetic lines in 12 hatches per line were analysed. Lines differed in their degree of selection for growth, with average live weights of 2.4, 2.1, 1.8 and 1.6 kg at 35 days of age for lines A, B, C and D, respectively, with all birds being fed on the same high quality food.
“And we found no significant difference in meal criteria between the lines. Similar patterns of bouting were observed across all the lines, and even the line with the highest growth rate showed a normal bouted structure,” said Miss Howie.
“The faster growing lines took longer and larger meals, but fewer per day than the slower growing lines – even when the effects of differences in stocking density were accounted for.”
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