Efficacy of heat treatment and sun drying of aflatoxin-contaminated feed for reducing the harmful biological effects in sheep

Drying causes degradation of aflatoxins in animal feed. The effect of drying aflatoxin contaminated feed in hot air oven or in sunlight on aflatoxin reduction was studied and was confirmed through a nutritional study in sheep. Four experimental diets were prepared using crushed maize, wheat bran and peanut meal. Diet I served as control and diets II, III and IV were treated with the required quantity of aflatoxin material to provide 350 ppb of aflatoxin B1 (AF B1). Diet II was not subjected to any physical treatment. Diet III was spread as thin layer in aluminium trays and dried in a hot air oven at 80 °C for 6 h and diet IV was dried in sunlight for 14 h (2 d, 25–37 °C ambient temperature). Twenty-four sheep of 12–16 months of age were distributed based on their body weight to four groups of six animals each in a completely randomized design. Each group was fed on one of the four diets as per requirement for maintenance and growth of 50 g/d. Feeding was continued for 150 d and daily feed intake and bi-weekly body weights were recorded. Blood was collected from each animal at 0, 100 and 150 d of feeding for estimation of biochemical parameters (haemoglobin, total protein, albumin, globulin, urea, triglycerides) and minerals (Ca, P, Mg, Cu, Zn). Analysis of aflatoxin showed that the control diet contained an average of 15 AF B1, whereas the aflatoxin-contaminated diet (II) contained 326 ppb AF B1. Hot air oven drying of the diet resulted in an average reduction of 57.6% in aflatoxin content, whereas sun drying reduced the aflatoxin content by 83.7%. Average feed intake did not differ significantly amongst the groups. Average daily weight gain was lower and feed conversion ratio was higher (P<0.01) in sheep fed the diet without drying. None of the blood biochemical parameters studied varied significantly between groups. However the Ca and P contents in plasma of sheep fed the aflatoxin-contaminated diet without drying for 150 d of feeding reduced significantly (P<0.05; <0.01). The levels of other minerals (Mg, Cu, Zn) however were not different among the four groups. It can be concluded that drying of feed either in hot air oven (80 °C, 6 h) or in sunlight (14 h) is effective in reducing the aflatoxin level and the harmful effects in sheep; the latter method of treatment is more effective and practical, and is less expensive.