Investigating how the type and quantity of food affect foraging behaviour and the neural circuits controlling feeding in broiler breeder chickens

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Broiler breeder chickens are food restricted to ensure good reproduction and health, but the resulting hunger is a welfare problem. Restriction of energy intake and growth by providing more of a lower energy density food (e.g. high dietary fibre) might reduce hunger. To determine this requires a better understanding of how the brain integrates information about the energy content and other aspects affecting satiety such as gut fill, and how this affects behaviour and feeding motivation.

The arcuate nucleus of the hypothalamus is key to the regulation of energy intake: AGRP mRNA is an integrated measure of hunger being responsive i) to both short and long term aspects of food intake, and ii) to manipulations of energy density. In a series of experiments, we will measure different variables relating to hunger in the same birds: i) home pen behaviour ii) foraging motivation by imposing a natural cost (of walking through water) on access to a foraging area without food (which avoids altering the hunger state). iii) expression of AGRP and related neuropeptides and receptors (POMC, CCKAR) iv) expression of gut hormone genes (CCK, Ghrelin, MCH, GLP-1).

We will investigate:
1) Diurnal and meal to meal variation using three feeding treatments (ad libitum (AL), am- and pm-fed rationed (R) birds) and sampling at 1,8 or 24hrs after feeding.
2) The effect of different levels of energy density will be identified by comparing R and AL fed controls with birds fed two different levels of dietary fibre (oat hulls) but with the same total energy intake and growth as R birds.
3) To identify how gut signals affect the arcuate nucleus, i) A model system using a standardised dietary fibre will be developed ii) the effect of crop or proventricular vagotomy will be separately compared iii) the effect of a CCKAR antagonist will be determined.
4) Commercially-relevant diets provided by a poultry breeding company will be tested to determine their effects on our hunger variables.

The poultry industry provides a major part of the world's protein in an efficient manner. However there are issues surrounding the breeding birds' management where research on the issue of how to control their growth whilst reducing the symptoms of hunger is required. This project will address the 'broiler breeder paradox', where food restriction is required to ensure the animals' welfare but the resulting hunger is seen as a welfare issue.

The principal benefit from this research will be a greater understanding of how diluting diets with fibre can improve welfare by producing satiety or a feeling of fullness. The project will deliver validated behavioural and physiological measurements of hunger and greater understanding of the way in which satiety and hunger in birds are controlled. We expect that by the end of the project we will have a clear assessment of whether fibre dilution does produce a signature of satiety in the brain and if commercially relevant diets can improve welfare. This will aid the poultry industry in identifying diets which enhance satiety and would represent a step towards solving the broiler breeder paradox.

This work will benefit the birds themselves, responding to societal concerns over animal welfare issues in intensive animal production systems. It will also help address an aspect of poultry production the industry itself would like to improve. The industry will benefit directly from the final part of the project where we will use the methods and knowledge developed to test the potential satiety benefits of practical diets developed by a major poultry breeding company. Our findings will enable breeding companies to implement changes in their dietary recommendations to producers. More generally, the methods and knowledge developed will enable the welfare benefits of other diluted diets or alternative feeding strategies to be appraised. This will be of interest to other stakeholders interested in the welfare of broiler breeders, such as animal welfare charities (e.g. RSPCA), pressure groups (e.g. CIWF) and other expert groups that advise policy makers (The Farm Animal Welfare Committee, European Food Standards Agency) and policy makers themselves (e.g. Defra).

The basic understanding of how dietary fibre can affect gut fill, inducing satiety, has potential impact beyond birds and as with many discoveries in the field of nutrition the chicken can be an excellent model. So in the efforts to fight obesity in humans and companion animals these findings have wider potential applications than the immediate target of the work.

We have a strong record of communication of our work to industry and other stakeholders through various routes. As well as presenting at discipline-specific academic conferences, we will target applied scientific conferences such as those of the WPSA which typically comprise 50% industry and 50% academia. We will also publish results in industry publications such as Poultry World (Deliverable 5) and produce a policy briefing made available on the Knowledge Scotland website (Deliverable 6). To ensure wider dissemination appropriate industry days and agricultural events (Pig and Poultry Fair; Deliverable 2) will be used along with a specific meeting organised to target the full range of organisations with an interest in this topic (Deliverable 3). This will be publicised through invitations to relevant contacts but also through web material and a press release (Deliverable 1), and summaries made available afterwards (Deliverable 4).