Apparent digestibility of ten protein ingredients for largemouth bass ( Micropterus salmoides )

The study was conducted to investigate the apparent digestibility coefficients (ADC) of nutrients in commonly used protein sources for largemouth bass. A reference diet and test diets with 70% reference diet and 30% feedstuff were formulated with yttrium oxide as a digestibility indicator. Overall, the ADC of dry matter of tested protein ingredients was 69.5%–96.4%, and the ADC of dry matter in animal protein sources was significantly higher than in the other five plant protein sources. The ADC of crude proteins ranged from 89.1% to 97.3% for all tested feedstuffs. The ADC value of total amino acids in the tested ingredients is consistent with that of the protein. The ADC of crude lipid of tested ingredients ranged from 45.4% to 96.2%, and the lowest and highest values were observed in porcine haemoglobin powder and pet-grade poultry by-product meal, respectively. The ADC of total phosphorus of animal protein ingredients, except porcine haemoglobin powder, was significantly higher than that of plant protein ingredients, except fermented soybean meal. The results revealed the difference in availability of nutrients in plant and animal protein sources for largemouth bass, which could provide a theoretical basis for the selection of protein sources of commercial feed for largemouth bass.