Physiological and metabolic responses of broilers to heat stress - implications for protein and amino acid nutrition

Abstract

When broilers are necessarily subjected to conditions of constant or cycling high temperatures, there is invariably consideration of changing diet formulation. Such changes may involve substitution of specific ingredients and/or alterations to nutrient levels in the diet. A primary concern is often the appropriate use of protein-rich ingredients and specifically their content of crude protein and amino acids. Broilers eat less at high temperatures, in an attempt to maintain homeothermy. Logically, diets will be fortified with protein and amino acids to counterbalance reduced intake. It is unclear if amino acids needs are altered, at high environmental temperatures, yet it is clear that any such change in level or balance is likely to be of lesser magnitude than change in feed intake. However, there is still controversy as to the direction of change for amino acids and protein under conditions of heat stress. There are specific concerns about the balance of certain amino acids, in particular arginine: lysine and also the source of any synthetic methionine added to correct apparent deficiencies. Balance of amino acids is described relative to pathways for polyamine metabolism.

Keywords::

• broiler
• temperature
• arginine
• lysine
• methionine
• amino acids