Current and future fish diets are facing increased variability in ingredient composition due to fishmeal and -oil replacement and due to a diversification in available ingredients for fish feeds. Consequently dietary macronutrient content might alter,including the carbohydrate fraction.For pigs,energy evaluation is done on a net-energy(NE) basis.In such systems,maintenance is assumed constant and the potential for energy retention is derived from the amount of digestible protein(DP),digestible fat(Dfat) and digestible carbohydrates(Dcbh) in feeds/ingredients.This study aimed to assess if for fish,the energy retention potential of diet(ingredient) can be estimated from the intake of digestible protein,fat and carbohydrate.A data set was used containing 8 experiments on Nile tilapia,Oreochromis niloticus(in total 68 groups of fish) done at 26-28¿in which digestibility of nutrients as well as complete energy balances were measured. Carbohydrates content of feed and faeces were calculated as nitrogen fat free extract(NFE).Initial body weight,growth rate,retained energy(RE) ranged between 40 to 140 g,0.7 to 4.0%,and 6 to 328 kJ/kg~(0.8)/d,respectively.Intake of DP,Dfat,Dcbh and digestible ash(Dash) ranged between 2.0 to 12.0 g/kg~(0.8)/d,0.3 to 5.7 g/kg~(0.8)/d,0.5 to 10.8 g/kg~(0.8)/d,and 0.2 to 0.8 g/kg~(0.8)/d,respectively. The net energy value of digestible nutrients was described by RE = -48.7(±2.64) + 12.2(±0.52)*DP + 36.7(±0.99)*Dfat + 11.9(±0.43)*Dcbh(R~2=0.99).Thus the efficiency of energy utilization of digestible nutrients for energy retention were estimated to be 52%,93%and 68%for respectively DP,Dfat and Dcbh,being slightly lower for DP and Dcbh compared to pigs.The residuals analysis indicated that digestible ash intake negatively affected RE(P0.05).Dash effects on RE disappeared if a fixed effect of experiment was included into the equation.This fixed effect of experiment(P0.001) indicates the presence for differences in energy requirements for maintenance between experiments.However,the inclusion of a fixed effect of experiment did not affect the NE estimates of the macro nutrients(i.e.,the regression coefficients).The results and use of net energy evaluation for fish are discussed in relation to:fish species(data sets on trout and turbot currently under construction);husbandry system;the aspect of variations in maintenance.This study suggests that a net energy evaluation for Nile tilapia,does not strongly differ from applied net energy evaluation systems in pigs.
|Title of host publication||The 14th International Symposium on Fish Nutrition and Feeding: Program & Abstracts. May 31-June 4, 2010, Qingdao, China|
|Place of Publication||Qingdao, China|
|Publication status||Published - 2010|
|Event||The 14th International Symposium on Fish Nutrition and Feeding. May 31-June 4, 2010, Qingdao, China - |
Duration: 31 May 2010 → 4 Jun 2010
|Conference||The 14th International Symposium on Fish Nutrition and Feeding. May 31-June 4, 2010, Qingdao, China|
|Period||31/05/10 → 4/06/10|