Chapter 9 Feeds and feeding
In: Tail biting in pigsSearch for other papers by Sandra Edwards in
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Abstract
Farmers in many countries rank deficiencies in feed composition and method of provision as among the most important risk factors for outbreaks of tail biting. Insufficient feeding space for the group when pigs are either meal-fed in long troughs or fed ad libitum from hoppers can result in sudden-forceful tail biting due to aggressive competition and frustration from inability to access feed. This is exacerbated by dividing the daily ration into many small meals, or by breakdowns or outages precluding an expected feed delivery. Deficits in the supply of energy, protein, minerals or micronutrients will induce a state of general or specific metabolic hunger which increases foraging motivation. In the absence of appropriate substrate in the environment, foraging behaviour can be redirected to penmates to cause two-stage tail biting. Hunger may be mitigated by dietary inclusion of some forms of fibre, but excessive dietary fibre may impair intake and digestion of other nutrients. Deficiencies or imbalances of some key amino acids can impair the synthesis of influential brain neurotransmitters regulating feeding, exploration and mood. This might exacerbate conditions predisposing biting and may contribute to development of pathological obsessive tail biting. Amino acid requirements are increased by high genetic lean growth potential or the presence of dietary antinutrients, and deficiencies or imbalances may also be induced by health challenges and gut inflammatory conditions. Other hypothesised mechanisms for dietary effects on tail biting risk include stress-induced changes in sodium metabolism, and behaviour and mood modification induced by microbiome dysbiosis via the microbiome-gut-brain axis. Further research is needed to elucidate these mechanisms and to indicate potential dietary interventions which can prevent and terminate damaging tail biting.