1. The effects of dietary aflatoxin (AF, 0.5, 1.0 and 2.0 mg/kg), ochratoxin (OA, 1.0, 2.0 and 4.0 mg/kg) or combinations of these on body weight gain, feed efficiency, organ weights and immune response were studied in broilers. 2. Significant growth depression, reduced food consumption and poor food conversion efficiency were recorded in broilers fed a diet containing the greater concentrations of AF (1 and 2 mg/kg) and OA (2 and 4 mg/kg). 3. The combination of 2 mg/kg AF and 4 mg/kg OA exerted the maximum adverse effect on growth, feed intake and feed efficiency, indicating a synergistic effect on performance. 4. AF at 2 mg/kg in the diet caused a significant increase in the relative weight of liver, whereas the relative weight of kidney was significantly increased at 4 mg/kg of OA. A significant decrease in the relative weight of the bursa of Fabricius was noted at the highest concentration of AF (2 mg/kg) and combinations of 1 and 2 mg/kg AF and 2 and 4 mg/kg OA. 5. Cell mediated immunity (CMI), in terms of mean skin thickness (MST) sensitive to dinitrochlorobenzene (DNCB), was significantly reduced in chicks given the combination of 2 mg/kg AF and 4 mg/kg OA. Haemagglutination (HA) titre against sheep red blood cells (SRBCs) peaked at 42 d of age. At 42 and 47 d of age, a significant decrease in HA titres was recorded in chicks given 4 mg/kg OA or a combination of AF (1 or 2 mg/kg) and OA (2 or 4 mg/kg). 6. AF at a dietary concentration of 1 mg/kg or more and OA at 2 mg/kg or more, either alone or in combination, caused severe reductions in growth and immune response.

1. A study was conducted with broilers to find out the effect of addition of methionine (0.0, 1.5, 3.0 and 4.5 g/kg) and choline (0.0, 1000 and 2000 mg/kg) to a basal diet containing crude protein, 221 g/kg, ME, 12.25 MJ/kg, methionine, 3.6 g/kg and choline, 1300 mg/kg. 2. Supplemental levels of methionine and choline were found to be ineffective in improving the growth, food consumption and food conversion efficiency of broilers. 3. However, a higher value for leucocyte migration inhibition was observed in chicks fed on the diet containing 6.5 g/kg methionine and 1300 mg/kg choline, indicating a significantly improved cellular immune response. 4. HI test and ELISA indicated enhanced antibody titres in chicks receiving 3.0 g/kg methionine and 3300 mg/kg choline, showing a significantly better humoral immune response. 5. Methionine and choline should be supplemented at levels higher than the recommended level of BIS for better health and production in chicks.

1. The effect of dietary vitamin E, selenium (Se) and their different combinations on body weight gain, food consumption, food conversion efficiency, leukocyte migration inhibition and antibody production was determined in broilers. 2. Chicks were fed on maize-soya bean based diets with concentrations of supplemental vitamin E varying from 0 to 300 IU/kg and selenium concentrations varying from 0 to 1 mg/kg either alone or in combination from 1 to 42 d of age. 3. The chicks were immunised for Newcastle Disease Virus (NDV) vaccine at 21 d. Per cent leukocyte migration inhibition (LMI) was studied on 42 d. Antibodies to NDV in serum were determined at 10 and 21 d post immunisation (PI). 4. Chicks receiving Se, 1 mg/kg and vitamin E 300 IU/kg had significantly higher cellular immune responses in terms of per cent LMI. 5. Maximum body weight gain and best efficiency of food utilisation were obtained in chicks fed diets containing 0.50 mg/kg Se and 300 IU/kg vitamin E. 6. Significantly higher antibody titres (HI and ELISA) at 10 d PI were attributed to 0.06 mg/kg and 150 IU/kg Se and vitamin E, respectively. 7. These data suggest that optimum growth and immune response may be achieved at supplemental level of Se of 0.06 mg/kg and vitamin E at 150 IU/kg. The vitamin E level is higher than that recommended by NRC (1984, 1994).

Studies were conducted to evaluate protein and energy utilisation in broilers fed diets containing various levels of aflatoxin (AF; 0, 0.5, 1 and 2 mg kg À1 ) and ochratoxin A (OA; 0, 1, 2 and 4 mg kg À1 ) either singly or in different combinations. Total protein efficiency (TPE) was reduced by 50.97, 76.52 and 132.75% at 2 mg kg À1 AF and 2 and 4 mg kg À1 OA respectively. Co-toxicity at two levels, 1 mg kg À1 AF þ 2 mg kg À1 OA and 2 mg kg À1 AF þ 4 mg kg À1 OA, resulted in significant reductions of 78.58 and 127.43% respectively in TPE. AF at all three levels and OA at 2 and 4 mg kg À1 caused significant decreases in net protein utilisation (NPU). Co-toxicity at all three levels led to significantly lower NPU. The reduction in NPU ranged from 18.68% at 0.5 mg kg À1 AF to 75.12% at 2 mg kg À1 AF þ 4 mg kg À1 OA. Significant reductions in metabolisable energy (ME) content were recorded at 1 and 2 mg kg À1 AF and all three levels of OA. ME content was reduced drastically when both toxins were fed simultaneously. It is suggested that both AF and OA adversely affect energy and protein utilisation in broilers, and this effect is exacerbated when both toxins are fed simultaneously. INTRODUCTIONNet protein utilisation (NPU) was found to be significantly lower and urinary nitrogen excretion significantly higher in ducklings fed a diet containing 30 mgkg À1 aflatoxin (AF) in comparison with those fed a toxin-free diet. 1 There was also a decrease in metabolisable energy (ME) content. 1 Graded levels of AF (1, 2 and 3 mg kg À1 ) significantly reduced the protein efficiency ratio and nitrogen absorbability in broilers. 2 It was also reported that ME was poorly utilised with 2 and 3 mg kg À1 dietary AF. 2 Dietary AF at a level of 1 mg kg À1 did not affect the digestibility of protein but caused a reduction in nitrogen utilisation from 31 to 43% and lowered the plasma concentration of methionine and cystine. 3 Ochratoxin A (OA) also caused malabsorption of nutrients. 4 Feeding of maize artificially contaminated with Penicillium spp and Aspergillus ochraceus to chicks resulted in reductions in dry matter and amino acid digestibility and energy utilisation. 5 AF at a rate of 1-2 mg kg À1 feed did not affect feed intake, protein digestibility or the absorption of amino acids, but reduced the utilisation of proteins. 6 Cereals can be contaminated by AFB 1 and OA and their metabolites before or during harvest or gradually during storage and processing. 7 The toxicity of individual mycotoxins can be enhanced or decreased when they occur as co-contaminants of feed,

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 (ME m /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.