Nitrogen-corrected apparent metabolizable energy value of macadamia nut cake for broiler chickens determined by difference and regression methods

Two energy balance experiments were conducted to determine the AME(n) value of Macadamia nut cake (MNC) for broiler chickens at different ages. In experiment 1, two dietary treatments were fed from 4 to 10 d of age. Dietary treatments consisted of a basal diet (no MNC) and a diet containing 60 g/kg of MNC (940 g/kg of basal diet + 60 g/kg of MNC). In experiment 2, four dietary treatments were provided from 17 to 23 d of age. Diets in second experiment were 1) basal control diet (no MNC); 2) 30 g/kg of MNC (970 g/kg of basal diet + 30 g/kg of MNC); 3) 60 g/kg of MNC (940 g/kg of basal diet + 60 g/kg of MNC); and 4) 90 g/kg of MNC (910 g/kg of basal diet + 90 g/kg of MNC). In experiment 2, broilers were restricted feeding in such a way that all the birds received the same amounts of basal diet, so that differences in AME(n) consumption were only due to MNC. A single source of MNC was used in both experiments. Feed intake, body weight, energy intake, energy excretion, N intake, N excretion, AME(n) intake and AME(n) were determined in both experiments. In experiment 1, the AME(n) was estimated using the difference method by subtracting AME(n) of the basal diet from AME(n) of the test diet. In experiment 2, AME(n) intake was regressed against feed intake with the slope estimating AME(n) of MNC. Regression equation used was Y = 2,908.2x - 122.73 (P < 0.001; SEM of the slope = 11.7; r(2) = 0.93). The AME(n) of MNC was found to be 12.09 and 12.17 MJ/kg in experiment 1 and 2, respectively with an average of 12.13 MJ/kg on DM basis. The results indicate that AME(n) of MNC is comparable to conventional feedstuffs with similar nutrient profile, thus can be incorporated in broiler diets.