THE EFFECT OF FREE FATTY-ACID CONTENT ON THE APPARENT METABOLIZABLE ENERGY OF COCONUT PALM KERNEL OIL FOR BROILER-CHICKENS AGED 12 AND 52 DAYS

A blend of coconut and palm kernel oil (CP; free fatty acid (FFA) cont ent 13.8 g kg-1 oil) together with its hydrolysed acid oil (CPAO; FFA content 839 g kg-1 oil) were obtained for evaluation. The two oils wer e blended in the proportions CP:CPAO 75:25, 50:50 and 25:75. The five oils (CP and CPAO, together with the three blends) were included in a basal diet at 40, 80 and 120 g kg-1. Experimental diets were evaluated for apparent metabolisable energy (AME) and apparent oil metabolisabi lity (AOM) with younger (12 days of age) and older (52 days of age) Ro ss I broiler chicks. The AME and AOM values for oils were determined f rom linear regression of AME and AOM of diets on rate of inclusion of oil. The AME values of oils were also determined as the product of AOM and gross energy/1000. The AME of oils varied from 32.2 to 22.6 MJ kg -1 with an increase in FFA content from 13.8 to 839 g kg-1 with younge r birds. Corresponding figures for older birds were 36.8 and 31.8 MJ k g-1. The reduction in AME with increasing FFA content appeared linear in both cases. AME of oil estimated from AOM of diets and oil gross en ergy followed a similar trend with a progressive reduction from 33.1 t o 25.8 MJ kg-1 (younger birds) and from 34.6 to 33.0 MJ kg-1 (older bi rds), with FFA increasing from 13.8 to 839 g kg-1 oil. The ratio of un saturated to saturated fatty acids (U/S) of oils was calculated in thr ee ways: (1) with all saturated fatty acids, (2) with myristic (C14:0) , palmitic (C16:0) and stearic (C18:0) fatty acids, (3) with palmitic and stearic fatty acids only appearing in the S fraction giving U/S va lues of 0.07, 2.51 or 7.82 respectively (U/S values are mean for the t wo oil sources). Comparison with predicted AME values revealed that a U/S of 2.52 gave an accurate estimate of the determined value, suggest ing that myristic acid behaves more like a saturated fatty acid but th at, in terms of metabolisability, shorter chain length saturated fatty acids resemble unsaturated fatty acids.