The digestible and metabolizable energy of two fat blends for growing pigs as influenced by level of inclusion

Abstract

AbstractTwo fat blends differing in free fatty acid concentration and fatty acid composition were included in cereal-based diets at concentrations of 10, 30, 50, 70, 90 and 110g/kg. The digestible (DE) and metabolizable (ME) energy of each diet were estimated in a metabolism experiment based on three 4 × 4 Latin squares using gilts of 30 kg initial live weight fitted with indwelling bladder catheters. With increasing dietary fat both DE and ME increased linearly (P < 0·001) and the linear equations derived were used to calculate the DE values of the two fats by extrapolation. Values were 26·4 and 24·2 MJ/kg respectively for fats A and B. The change in dietary D E and ME to increasing dietary fat concentration showed a curvilinear trend (P = 0·0987 and 0·1268 respectively for DE and ME ) indicating that fats may not be correctly evaluated at only one rate of inclusion. The quadratic functions derived were interpolated to provide DE and ME data for the two fats. Values for DE for fat A ranged from 32·7 o t 25·7 MJ/kg at 10 and HOg/kg, and for fat B from 38·6 to 26·3 MJ/kg at 10 and 110 g/kg. Data for ME followed similar trends. It was concluded that multi-level assays are important in the evaluation of fats and that the rate of decline of fat DE and ME was specific to the fat examined.