Effect of aflatoxin, ochratoxin and their combination on protein and energy utilisation in white leghorn laying hens

The effect of dietary aflatoxin B-1 (AF) at levels of 0.5, 1 and 2 mg kg(-1), ochratoxin A (OA) at levels of 1, 2 and 4 mg kg(-1) and their corresponding combinations on protein and energy utilisation as well as energy partitioning was studied in white leghorn laying hens. Protein retention was adversely affected at all levels of AF and OA either singly or in combination, though the effect was more evident with OA and AF + OA. Minimum protein retention was recorded in hens fed the combination of toxins at their highest levels (2 mg kg(-1) AF + 4 mg kg(-1) OA). Aflatoxin at 1 and 2 mg kg(-1) and OA and AF + OA at all levels caused a significant reduction in metabolisable energy (ME) value of the diets. The minimum ME value was recorded for the diet containing both toxins at their highest levels (2 mg kg(-1) AF + 4 mg kg(-1) OA). A significant depression in egg energy deposition was observed with dietary inclusion of 1 and 2 mg kg(-1) AF, 2 and 4 mg kg(-1) OA and all levels of AF + OA in period I. In period II the reduction in egg energy deposition was significant at all levels of toxins either singly or in combination. Body energy deposition was adversely affected in hens fed the highest levels of AF (2 mg kg(-1)) and OA (4 mg kg(-1)) and all levels of AF + OA in period I. However, in period II a significant decrease in body energy deposition was observed at all levels of toxins except 1 mg kg(-1) OA. A significant increase in maintenance energy (MEm/W-0.75 day(-1)) requirement was recorded in hens fed 2 mg kg(-1) AF, 4 mg kg(-1) OA and all levels of AF + OA. It is suggested that AF and OA either singly or in combination affect not only protein and energy utilisation in laying hens but also energy partitioning i.e. egg and body energy deposition and maintenance energy requirement. However, the combination of toxins (AF + OA) has more severe adverse effects on all parameters than the individual toxins because of their synergistic toxicity effect. (c) 2007 Society of Chemical Industry.