:Two experiments were conducted to establish a digestible energy (DE) content prediction model of rapeseed meal for growing-finishing pig based on rapeseed meal's chemical composition. In experiment 1, observed linear relationships between the determined DE content of 22 rapeseed meal calibration samples and proximate nutrients, gross energy (GE) and neutral detergent fiber (NDF) were used to develop the DE prediction model. In experiment 2, 4 samples of rapeseed meal selected at random from the primary rapeseed growing regions of China were used for testing the accuracy of DE prediction models. The results indicated that the DE was negatively correlated with NDF (r = -0.86) and acid detergent fiber (ADF) (r = -0.73) contents, and moderately correlated with gross energy (GE; r = 0.56) content in rapeseed meal calibration samples. In contrast, no significant correlations were found for crude protein, ether extract, crude fiber and ash contents. According to the regression analysis, NDF or both NDF and GE were found to be useful for the DE prediction models. Two prediction models: DE = 16.775-0.147NDF (R 2 = 0.73) and DE = 11.848-0.131NDF+0.231GE (R 2 = 0.76) were obtained. The maximum absolute difference between the in vivo DE determinations and the predicted DE values was 0.62 MJ/kg and the relative difference was 5.21%. Therefore, it was concluded that, for growing-finishing pigs, these two prediction models could be used to predict the DE content of rapeseed meal with acceptable accuracy.
Summary A feeding trial was conducted to study the effect of partial replacement of dietary monocalcium phosphate (MCP) with phytase on growth performance, feed utilization and phosphorus discharge in black sea bream, Acanthopagrus schlegelii. In the feeding trial, the control diet (designated as P1.5) was prepared with 1.5% MCP but without phytase, and the three other diets (designated as PP1.0, PP0.5 and PP0, respectively) were supplemented with 1.0%, 0.5% and 0% MCP, respectively, along with 200 mg (400 U) phytase/kg diet in each. Each diet was tested in triplicate tanks and fish were fed twice daily to satiation. After an 8‐week feeding trial in indoor flow‐through cylindrical fibreglass tanks (25 fish per tank, initial body weight: 11.5 ± 0.12 g), fish fed with PP1.0 and PP0.5 had no significant change in weight gain (WG), specific growth rate (SGR), protein efficiency rate (PER) or feed conversion ratio (FCR) compared to the control (p > .05), whereas fish fed with PP0 showed a significantly lower growth performance in the above parameters (p < .05). The addition of phytase did not affect the body composition or muscle composition. The apparent digestibility coefficients (ADCs) of crude protein and phosphorus increased when fish were fed diets in which MCP was replaced by phytase. Phosphorus discharge was also significantly reduced in fish fed diets in which MCP was replaced by phytase (10.2 ± 0.50 to 8.01 ± 0.47 g/kg weight gain). The present study suggests that dietary MCP can be reduced when phytase is added to the black sea bream diet, with a maximum MCP reduction level of up to 1% when phytase is supplemented at 200 mg (400 U)/kg diet. Thus, phytase in the diet of black sea bream is economically and ecologically beneficial.
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