Determination Of Digestibility Of Selected Protein Sources And Evaluation Of Feed Formulation Based On Their Availability For Pacific White Shrimp, Litopenaeus Vannamei

In this paper, the nutrient digestibility of different protein feed ingredients were evaluated using in vitro and in vivo methods for Pacific white shrimp, Litopenaeus vannamei. Based on digestibility of these protein feed ingredients, five practical diets were formulated to contain the same level of digestible crude protein and digestible amino acids for the shrimp, and their effect on growth performance, body compositions, feed utilization, digestive enzyme activity and biochemical parameters were assessed. In addition, the effect of replacement fish meal by peanut meal in practical diets on growth performance for the shrimp was also investigated. The results were as follows:Experiment 1: The digestibility of four protein feed ingredients [fish meal (FM), soybean meal (SM), rapeseed meal (RM) and peanut meal (PM)] were determined using the in vitro method and kinetics of hydrolysis of digestive enzymes in stomach, hepatopancreas and intestine of Pacific white shrimp were studied. The results showed that the order of digestion of different digestive organs for dry matter was stomach > hepatopancreas > intestine, and stomach had significantly higher dry matter digestibility of FM than hepatopancreas and intestine (P<0.05), but intestine got significantly lower dry matter digestibility of PM than stomach and hepatopancreas (P<0.05). The order of digestion of different digestive organs for crude protein was hepatopancreas > stomach > intestine, and the digestibility of PM and RM in intestin were significantly lower than in stomach and hepatopancreas (P<0.05), but the digestibility of FM in hepatopancreas was significantly higher than in stomach and intestine (P<0.05). The order of proteins for digestibility of dry matter was SM (50.78%) > RM (42.02%) > PM (39.67%) > FM (36.50%). The order proteins for digestibility of crude protein was PM (60.40%) > SM (56.45%) > FM (46.28%) > RM (43.28%). The amino acids production of enzymolysis reaction was hepatopancreas (96.72 mg) > stomach (31.28 mg) > intestine (27.58 mg); the order of enzymolysis rate for amino acid was PM (3.9154 mg/h) > FM (3.4774 mg/h) > SM (2.8316 mg/h) > RM (2.7404 mg/h).Experiment 2: A feeding trial was conducted to determined apparent digestibility coefficients (ADC) of dry matter, crude protein, crude lipid, ash, energy and amino acids for twelve protein feed ingredients (i.e. fish meal, blood meal, meat and bone meal, poultry by-products meal, shrimp head meal, squid visceral meal, soybean meal, rapeseed meal, cottonseed meal, peanut meal, corn gluten meal and brewers yeast) for Pacific white shrimp (4.45±0.21 g). A reference diet and test diets (consisted of 70% reference diet and 30% of the raw feedstuff, except for blood meal with a ratio of 85%:15%) were used with Cr2O3 as external indicator. The results showed that the ADC of dry matter ranged from 48.61% to 86.98%, the ADC of energy ranged from 51.11% to 97.27%, the ADC of crude protein ranged from 55.74% to 92.35%, the ADC of crude lipid ranged from -0.23% to 92.64%, and the ADC of ash between 60.83% and 96.30%. The ADCs of total amino acids for fish meal, soybean meal and peanut meal were significantly higher than that for other meals (P<0.05), while corn gluten meal was significantly lower than that for other meals (P<0.05), and those feed ingredients were: soybean meal (92.67%) > peanut meal (90.61%) > fish meal (90.56%)> poultry by-products (89.81%) > shrimp head meal (88.82%) > brewers yeast (86.23%) > rapeseed meal (84.84%) > meat-bone meal (83.87%) > squid visceral meal (83.72%) > blood meal (77.25%) > cottonseed meal (72.82%) > corn gluten meal (59.15%).Experiment 3: A feeding trial was conducted to evaluate the effect of five practical diets formulated on the same level of digestible crude protein, lysine, methionine and arginine on growth performance, body composition, feed utilization, digestive enzyme activity and values of biochemical parameters for the shrimp. The results showed that weight gain rate, survival, specific growth rate and protease activity in stomach in shrimp fed the diet at the fish meal inclusion level of 10% were significantly lower than that of shrimp fed the diets at the level of 15% or higher (P<0.05), while hepatosomatic indexes, blood urea nitrogen and lysozyme activities increased significantly (P<0.05). There were no differences in growth performance, body composition, digestive enzyme activity, blood urea nitrogen level, glutamic-pyruvic transaminase, glutamic-oxalacetic transaminase and lysozyme activities between the fish meal diets at the inclusion level of 15% or higher (P>0.05). Feed conversion rate and feeding rate increased, while protein efficiency ratio and apparent digestibility coefficients of dry matter, crude protein and crude lipid decreased with the reduction in dietary fish meal inclusion level.Experiment 4: Six isonitrogenous (crude protein 41%) and isolipidic (crude lipid 8.5%) diets were formulated to contain 0%, 7%, 14%, 21%, 28% and 35% of peanut meal (PM), replacing 0%, 15%, 30%, 45%, 60% and 75% of fish meal (FM) protein respectively. Chromic oxide was used as the inert indicator for digestibility. The results showed that weight gain rate decreased significantly when dietary PM inclusion was raised above 21% (P<0.05). Protein efficiency ratio and survival rate decreased significantly but feed conversion rate increased significantly as PM inclusion level above 14% (P<0.05). Feeding rate in 21% PM inclusion group was significantly higher than that in 28% and 35% PM inclusion groups (P<0.05). Body crude protein and ash content significantly decreased, but body moisture significantly increased when dietary PM inclusion was higher than 14% (P<0.05). The apparent digestibility for dry matter, crude protein, crude lipids and ash decreased gradually as the level of PM replacement increased. Protease activities in stomach and hepatopancreas of 0~14% PM inclusion groups were significantly higher than in other groups (P<0.05). There was a similar trend as digestibility for the activities of superoxide dismutase (SOD), peroxidase (POD), acid phosphatase (ACP) and alkaline phosphatase (AKP) in serum, but ceruloplasmin (CP) content displayed adverse tendency. Body lipid and lysozyme activity was not affected by all treatments (P>0.05).