Study on Utilization of Alternate Plant Protein Sources in Tilapia (Oreochromis Niloticus) Diets
|School||Huazhong Agricultural University|
|Keywords||Oreochromis niloticus plant protein mixture cottonseed meal detoxification growth apparent digestibility|
The study was conducted to Oreochromis niloticus, the effects of fish meal replacement by plant protein sources on growth performance, body composition and apparent digestibility, and using cottonseed meal treated with two methods for detoxification of gossypol as a partial substitution of soybean meal. The contents and results are as follows:1.A study with increasing levels of a plant protein mixture (PM) replacing fish meal (FM) in diets for juvenile Nile tilapia, was conducted to elucidate effects on growth performance, body conposition and digestibility. The PM was consisted of 25% cottonseed meal,25% rapeseed meal,25% corn gulten meal and 25% broad bean. Five isonitrogenous (crude protein 30%) and isoenergetic (20 KJ/g) diets replacing 0% (control),25% (PM25),50% (PM50),75% (PM75) and 100% (PM100) of the FM with PM were formulated. Each experimental diet was fed to triplicate groups of 30 Nile tilapia juveniles (initial body weight 7.16±0.81 g) in 400 L aquaria for 10 weeks.The water temperature was (21±0.5)℃,and dissolved oxygen was approximately 5.0 mg/L during the experimental period. The results showed that weight gain rate (WGR),specific growth rate (SGR), feed conversion ratio (FCR) and protein efficiency ratio (PER) of fish fed diets PM25,PM50, PM75 were not significantly different from those of fish fed control diet (P>0.05), while fish fed PM100 had significant difference with those of fish fed the other diets.No significant differences in HSI and VSI were observed among dietary treaments.The whole body proximate analysis showed that protein and ash contents significantly decreased with increasing dietary PM levels, while the whole body lipid content showed increased. Except hisidine content was increased with increasing dietary PM levels, there were no significant effects on muscle indispensable amino acid (IAA) and total amino acid contents.Taste amino acid to total amino acid ratio decreased with increasing dietary PM levels, and no effect on total amino acid content was observed (P>0.05).PM substitution up to 75% of the FM protein did not result in differences in the apparent digestibility of protein and total amino acid compared with the control(P>0.05), whereas in the PM100 group digestibility was significantly lower than the other groups (P<0.05);no significant effects were found on lipid digestibility (P>0.05).These results suggest that 75% FM replacement by PM caused no significant effect on the growth, body composition and digestibility of Nile tilapia.2.The cottoseed meal used in this experiment was treated with ferrous sulfate and heated for detoxification of gossypol, then was used to replace 33%,67% soybean meal. The objective was to study the effect of different treatments on the reduction of gossypol level. Seven isonitrogenous (33% crude protein) and isoenergetic(19 KJ/g) diets were formulated. Each experimental diet was fed to triplicate groups of 30 Nile tilapia juveniles (initial body weight 7.27±0.25 g) in 400 L aquaria for 10 weeks.The water temperature was (21±0.5)℃,and dissolved oxygen was approximately 5.0 mg/L during the experimental period. The result showed that the detoxification treatments were beneficial for the reduction of free gossypol, the free gossypol content of diets treated with ferrous sulfate and heated (44.80 mg/kg,70.02 mg/kg; 32.43 mg/kg,43.23 mg/kg) were significantly lower than the untreated diet(198.14 mg/kg,267.02 mg/kg). Detoxification treatment markedly reduced the free gossypol contents of liver and kidney (P<0.05);No significant differences were observed in weight gain rate (WGR),specific growth rate (SGR),survival rate (SR) among dietary treatments (P>0.05);Detoxification treatments had no significant effects on protein and lipid contents, while, the ash content of untreated group was significantly higher than that of control group (P<0.05), the ash content of detoxification treated group was similar with the control group (P>0.05);No significant differences in HSI and VSI were observed among dietary treaments (P>0.05), however, aspartate aminotransferase and alanine aminotransferase activities of untreated group were significantly higher than detoxification treated and control groups (P<0.05), which showed that the free gossypol content of cottonseed meal can bring the abnormity of liver function. In conclusion, the free gossypol content of cottonseed meal had significant effect on liver function, the detoxification treatment was beneficial to reduce the content of free gossypol, improve the utilization of cottonseed meal.