THE EFFECTS OF ENZYMATIC HYDROLYSATES OF FEATHERS AND COLLAGEN IN DIETS FOR BROILER CHICKS (Gallus gallus L.) ON MEAT QUALITY

Abstract

The deficit of feed-grade protein for the productive animals and poultry is presently propelling the interest toward the use of the hydrolysates of slaughter wastes as the potential protein sources. The slaughter wastes of poultry (feathers, intestines, blood, heads, shanks, meat-bone residues of the deboning) can mount up to one third of the initial bodyweight. Earlier we have developed the two-stage technology of easily digestible protein additives involving the hydrolysis and fermentation of protein from poultry slaughter wastes (primarily keratin from feathers and collagen from meat-bone residue). The study presented is a pioneer evidence that the substitution of these additives for fishmeal in diets for broilers provides more rapid growth and does not deteriorate the protein, fatty and amino acid profiles, concentrations of non-peptide, peptide and residual nitrogen, technological properties of meat. The study was performed in 2019 and aimed at the comparative evaluation of meat quality at 38 and 49 days of age in floor-housed broilers fed standard diet and three experimental diets with these hydrolysates. The broilers (cross Ross-308, 35 birds per treatment) kept in conditions of the Center for Genetics & Selection “EPH Zagorskoye” (Moscow Province) were allotted to four treatments partially slaughtered at 38 days of age and partially at 49 days. Control treatment 1 was fed a standard broiler diet with fishmeal; in experimental treatments fishmeal was substituted by enzymatic hydrolysate of feathers (treatment 2), enzymatic hydrolysate of collagen (treatment 3), mixture of these two hydrolysates with addition of probiotic Bacell M (0.2 %), and bran (0.5 %) as a source of vegetable fiber (treatment 4). It was found that supplementation of diets with the hydrolysates of keratin and collagen significantly improved live bodyweight in broilers by 8.78-10.89 % in compare to control (p £ 0.001). The content of peptide nitrogen in breast muscles in treatments 1 and 4 tended to grow with the increase in slaughter age (in treatment 1 from 0.07 at 38 days to 0.27 % at 49 days; in treatment 4 from 0.07 to 0.35 %). The number of protein fractions (with molecular weights from 100 to < 20 KDa) in meat increased with slaughter age with all studied diets. Protein of breast muscles contained more isoleucine, leucine, valine, and phenylalanine at 38 and 49 days of age in compare to thigh meat with all studied diets. The digestibility of essential amino acids in breast muscles in treatment 4 grew from 81.78 % with slaughter at 38 days to 90.29 % at 49 days. Evaluation of biological value of meat revealed better balanced ratios of the essential amino acids in breast muscles in control treatment at 38 days of age (the difference in the amino acid score 70.53 %) and in treatment 4 at 49 days of age (the difference in the amino acid score 66.48 %). In thigh meat this difference was higher in treatment 3 at 38 days of age (59.69 %) and in treatment 4 at 49 days of age (61.43 %). There were no significant differences between the treatments in concentrations of fatty acids in meat. The conclusion was made that the use of new protein additives based on the enzymatic hydrolysates of feathers and collagen in diets for broilers does not deteriorate the parameters of meat quality.