Protein source affects apparent digestibility of feed ingredients and protein metabolism in Chinese perch (Siniperca chuatsi)

In previous studies of apparent digestibility coefficients (ADCs), the association between apparent digestion and protein metabolism from different protein sources has long been ignored. To develop nutritionally adequate diets, this study evaluated the effects of different protein sources (fermented soybean meal [FSM], rapeseed meal [RSM], Antarctic krill powder [AKP] and fish protein hydrolysate [FPH]) on the growth performance, ADCs and expression of genes related to protein metabolism in Chinese perch. The experimental feed was composed of 300g kg(-1) test ingredients and 700g kg(-1) reference feed (RF). After the feeding trial, FPH was found to achieve the best growth performance of Chinese perch and had significantly higher ADCs of dry matter and gross energy than all other ingredients. Besides, FPH was the only ingredient with crude protein ADC exceeding 90% and the highest crude lipid ADC, while RSM had the lowest crude protein and crude lipid ADC. FPH showed the highest ADC of amino acids except for serine and tyrosine, and RSM showed the lowest amino acid ADC except for methionine. FPH resulted in the lowest expression of mtor, s6k, murf1, mafbx, pept2 and lat2 and the highest expression of gdh and ast in the muscle. The transcription level of cat significantly increased in the gut of the FSM group compared with that in the RF group. These findings imply that FPH may be a promising ingredient to be incorporated into the formulated diet of Chinese perch.