Fats are important but variable energy-yielding ingredients in diets for broilers. One of the factors that may affect the dietary energy value of fats is the proportion of free fatty acids which, together with rate of inclusion of fat and the age of the bird, must be considered in fat evaluation. The current experiment was designed to investigate the effect of free fatty acid content of tallow on the apparent metabolisable energy values for broilers.

Tallow and tallow acid oil (Table 1) were obtained for evaluation. Tallow (A) of free fatty acid content 138.4 g/kg was hydrolysed to produce a fat (E) of free fatty acid (FFA) content 952.1 g/kg. Fat A and B were blended in the proportions A75:B25, A50:B50 and A25:B75 giving fats of 341.5, 545.3 and 748.7 g/kg FFA respectively which were included at rates of 40 g/kg, 80 g/kg and 120 g/kg at the expense of the energy-yielding ingredients. The 16 experimental diets - basal (Table 2) together with 15 containing fats - were evaluated with Ross 1 broiler chicks of 1.5 weeks (5 replicates of cage of 2 birds) and 7.5 weeks of age (5 replicates of cage of 1 bird).