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Research Training Scholarships

Louise Buckley

“Choices for hungry broiler breeders: do they prefer qualitative food restriction to quantitative food restriction?”

Increasingly large numbers of meat chickens (broilers) are reared every year to satisfy a growing consumer demand for poultry (in the UK alone approximately 900 million broilers are killed annually). To ensure broiler chicken production is as economical as possible, broiler birds have undergone intense genetic selection for increased rate of growth and feed conversion efficiency. A broiler chick can grow from hatch to slaughter weight (approximately 2 kg) in as little as 35 days. However, this rapid growth rate has not come without a cost to the chicken and welfare problems often affect broiler birds reared for slaughter and parent stock reared for egg production.

In 2007 UFAW awarded an Animal Welfare Research Training Scholarship to Louise Buckley to investigate the welfare of broiler breeders. Broiler breeders, as are their progeny, are highly motivated to eat and also to consume large amounts of food. However, although this is a desirable trait in broiler birds that will be slaughtered at a few weeks old for market, it is incompatible with rearing breeder birds who must remain healthy and reproductively viable as they grow to sexual maturity and reach point of lay (breeder birds are usually slaughtered at approximately 60 weeks old). Consequently, the amount of food given to broiler breeders is routinely severely restricted and, as a result, broiler breeders experience chronic hunger. Chronic hunger is a welfare problem due to the increased likelihood of stereotypic behaviours, aggression, cannibalism and polydipsia (excessive thirst and drinking). There are approximately 7.5 million broiler breeders in UK production systems at any one time.

Louise sought to investigate whether broiler breeder welfare may be improved by qualitative, compared to quantitative, food restriction. Various researchers have explored qualitative restriction of broiler breeder diets through manipulating the quality of the diet by the addition of lots of fibre and / or other compounds thought to have an appetite supressing function. Researchers at the Scottish Agricultural College (now SRUC) successfully created a qualitative restricted diet that allowed broiler breeders to feed ad libitum but still grow to a healthy, commercially viable bodyweight. However, it was unclear whether this was achieved through improved satiety (a positive welfare effect) or decreased palatability of the diet (a negative welfare affect).

The aim of Louise’s PhD research was to use choice test methodologies to find out whether broiler breeders wanted a quantity – or quality – restricted diet. The underlying assumption was that if these quality-restricted diets made the broiler breeders feel more satiated, they would prefer them. This proved to be a more challenging task than was anticipated. In the initial study that used a T maze task, Louise found that broiler breeders could discriminate easily between a food / no food task, but failed to demonstrate a preference between different diets offered. A subsequent study demonstrated that it was likely that this failure to show a preference was affected by the level of hunger that the birds were experiencing as birds reared to commercial levels of feed restriction found it impossible to learn a food quantity discrimination task that birds that were much less hungry could learn.

Further experiments applied conditioned place preference and state–dependent learning methodologies to the problem but the birds still failed to show preferences that would indicate indirectly a preference for either qualitative or quantitative dietary restriction. Louise concluded that her research indicated that there was no evidence that the broiler breeders wanted a diet that was quality restricted, but acknowledges that the cognitive impact of hunger made preference testing problematic.

Louise graduated from her PhD studies in July 2012 and now works at Harper Adams University as a lecturer within the Department for Animal Production, Welfare & Veterinary Sciences. She is now the University – UFAW LINK contact at her institution.

Published papers arising from Louise’s project supported by UFAW:

Buckley, L.A., Sandilands, V., Hocking, P.M., Tolkamp, B.J., D’Eath, R.B. 2015. Feed-restricted broiler breeders: State dependent learning as a novel welfare assessment tool to evaluate their hunger state? Applied Animal Behaviour Science. 165: 124–132.

Buckley, L.A., Sandilands, V., Hocking, P.M., Tolkamp, B.J., D’Eath, R.B. 2012. The use of conditioned place preference to determine broiler preferences for quantitative or qualitative dietary restriction. British Poultry Science, 53(3): 291 – 306.

Buckley, L. A., Sandilands, V., Tolkamp, B. J. and D'Eath, R. B. 2011. Quantifying hungry broiler breeder dietary preferences using a closed economy T - maze task. Applied Animal Behaviour Science133 (3): 216 – 227,

Buckley, L. A., MacMillan, L. M., Sandilands, V., Hocking, P., Tolkamp, B. J. and D'Eath, R. B. 2011. Too hungry to learn? Hungry broiler breeders fail to learn a Y-maze food quantity discrimination task. Animal Welfare. 20: 469 – 481