Apparent Digestibility of key feed ingredients by largemouth bass (Micropterus salmoides)
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- Master’s theses (BioVit) 
The aim of this project was to determine apparent digestibility coefficients (ADC) of macronutrients, amino acids (AA), phosphorus (P) and energy (EN) in protein-rich ingredients in extruded diets for largemouth bass (Micropterus salmoides). Digestibilities were assessed by the ingredient replacement method. Yttrium oxide was used as inert marker and faeces was collected by manual stripping. Peruvian anchovy fishmeal (PAF) was the sole protein source in the reference diet. Each ingredient was examined in triplicate with 30% replacement. Animal protein ingredients included four fishmeals (Peruvian anchovy fishmeal PAF, three Chinese fishmeals made from sardine CSF, anchovy CAF or mackerel CMF), four sources of poultry by-products (poultry by-product meal PBM, poultry carcass meal PCM, hydrolysed feather meal HFM, spray-dried granulated inedible egg product SGE) and two potential alternative animal protein ingredients (defatted Tenebrio molitor beetle larvae meal DTM, and hydrolysates of stickwater and soybean HSS). The results showed that the apparent digestibility coefficients (ADC) of dry matter (DM, ranging from 67.0 to 96.4% ), EN (75.6-98.6%) and crude protein (CP, 72.0-95.3%) for animal protein ingredients varied considerably. The ADC of SGE was significantly higher than others, while the ADCs of HFM and DTM were lowest. ADCs of DM (77.4-86.2%), EN (81.8-94.4%) and CP (84.7-88.9%) for other ingredients were quite close. ADCs of proteins in animal ingredients reflected the ADCs of total amino acids. The ADC of P showed no significant difference except for CMF (37.2%) and PAF (61.7%). All values for ADC of P were low. Plant protein ingredients included soybean products (soybean meal SBM, soy protein concentrate SPC, two fermented soybean meals TB FSM-TB and YH FSM-YH), and cottonseed products (cottonseed meal CSM, degossypolled cottonseed protein TY DCP-TY, degossypolled cottonseed protein JL DCP-JL). The results showed that ADCs of DM (55.0-78.0%) and EN (67.0-84.8%) in the plant ingredients varied greatly. Compared with PAF, DM and EN digestibility of SPC and SBM showed no significant difference, while that of other raw materials were significantly lower (P < 0.05). ADCs of DM was highly correlated (r = 0.95) with ADC of energy. ADC of CP for all plant ingredients were high and only varied moderately (83.1-96.5%). ADC of CP of the soy products was significantly (P < 0.05) higher than that of the fish meal. No significant difference was seen among the cottonseed products. ADCs of total amino acids (AA) was highly correlated (r = 0.93) with the ADCs of CP. Overall, ADCs of DM, CP, AA and EN of SGE were highest in animal protein ingredients, followed by PBM and PCM. ADCs of four sources of fish meal and HSS were slightly lower (67.0-84.8%) than those of animal products. The ADCs in HFM and DTM were significantly lower than that of any of the other ingredients. The results showed that all animal protein ingredients except HFM and DTM can be used as main protein sources for largemouth bass. HFM and DTM should only added as a part of a mix of protein sources in the diet, and essential amino acids must be added to achieve balanced composition. The requirement of phosphorus in fish must be noted, in view of the low values for ADC of P in the tested ingredients. In plant protein ingredients, the ADC of P was highly variable. ADC of P of PAF, SPC and SBM were not significantly different, while ADCs of FSM-TB, FSM-YH, CSM, DCP-TY and DCP-JL were significantly lower. Therefore, SPC and SBM can replace fish meal as the main protein source in largemouth bass diets, while the usage of other protein-rich ingredients should be limited. The absence significant difference of PAF in the reference diet tested in two experiments. This indicates that slightly different rearing conditions did not significantly affect the results, and that the results obtained in these experiments were repeatable and reliable.Målet med dette prosjektet var å bestemme fordøyelighet av makro-næringsstoff, aminosyrer (AA), fosfor (P) og energi (EN) i ekstruderte fôr til «largemouth bass» (Micropterus salmoides). Fordøyeligheter ble bestemt ved hjelp av utbyttingsmetoden. Yttriumoksyd ble benyttet som inert markør, og faeces ble samlet inn ved å stryke fisken. Peruansk fiskemel av ansjos (PAF) var eneste proteinkilde i referansefôret. Hver ingrediens ble bestemt med 3 gjentak med 30% utbytting.