Valorization of chicken intestine: A process of protein hydrolysate for fish feed attractant using pilot plant scale system

Chicken intestine as a poultry industry byproduct is rich in protein, contains various endogenous enzymes and can be prepared as a hydrolysate via autolysis. This research examined the physico-chemical properties of chicken hydrolysate as a feed attractant. Growth of fish fed on the chicken hydrolysate-coated diet was compared with fish fed on a commercial hydrolysate (C). Three chicken hydrolysates were prepared at 60 degrees C for 4 h on a pilot plant scale including autolysis at pH 3 (S1), supplemental enzyme addition at pH 6.11 (S2) and a combination of supplemental enzyme addition following autolysis at pH 3 (S3). Highest yield was found in S2 (76%) followed by S3 (74%) and S1 (72%). The chicken hydrolysate had lower protein content (13-16%), higher fat (21-23%) and lower viscosity at 7429-10607 cP compared with C. Degrees of hydrolysis (DH) of S1, S2, S3 and C were 56%, 73%, 65% and 61%, respectively. Highest number of peptides less than 3 kDa associated with feed palatability was found in S2 (76%), followed by S3 (49%), C (29%) and S1 (28%). The three chicken hydrolysates were rich in essential amino acids similar to the C sample but with smaller amounts of amino acids in S1 and S3 due to the acidic pH preparation. An 8-week feeding trial of two selected fish species (hybrid catfish and Nile tilapia) was conducted in a water -recirculation system to investigate the effect of different hydrolysate-coated diets on fish growth performance. Highest body weight of hybrid catfish at 65.20 g gave weight gain of 150.15% and specific growth rate 1.73% d- 1. Optimal feed conversion ratio (FCR) at 1.49 was observed in the S2 diet (p < 0.05). Improved growth performance was observed in Nile tilapia for diets coated with all chicken hydrolysates but no significant difference was found (p >= 0.05). Highest values of the he-matological parameters, including hemoglobin, hematocrit and mean corpuscular hemoglobin concentration, were found in the two fish groups fed with S1, S2 and S3 diets (p < 0.05). At the end of the experiment, hybrid catfish and Nile tilapia fed with the S2 and S3 diets had the highest fish body protein content at 17% and 16%, respectively (p < 0.05). Our results showed that the three chicken hydrolysates, particularly S2, could potentially be used as feed attractants for freshwater fish.

Automated summary

Three chicken hydrolysates, particularly S2, can be used as feed attractants for freshwater fish.