THE NUTRITIONAL VALUE OF POULTRY BY-PRODUCT MEAL G. M. PESTI* ABSTRACT

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1 THE NUTRITIONAL VALUE OF POULTRY BY-PRODUCT MEAL G. M. PESTI* ABSTRACT for their nutritional content. The metabolizable energy of the samples (nitrogen corrected) could be predicted fairly accurately from the ash and protein 'contents of the ingredients. PBPM samples of relatively high and low qualities were incorporated into corn and soybean meal-based diets at the 5% level on an isoenergetic and isonitrogenous basis. Significant differences in chick growth or feed efficiency due to PBPM sample quality could not be detected. INTRODUCTION The composition of the poultry by-product meal (PBPM) now being fed is different from those in many experiments on PBPM nutritional value. For instance, the change of the broiler industry to further processing, particularly deboning, makes more bones available to be added to the PBPM. Further, the legal definition of PBPM is not always considered when "PBPM" is traded: "... the ground, dry-rendered or wet-rendered clean parts of the carcass of slaughtered poultry... It must contain not more than 16% ash and not more than 4% acid-insoluble ash". Often hatchery waste and/or disolved air flotation (DAF) sludge is added to the offal before processing. Several studies established that PBPM could be added to broiler diets with good results (Romoser, 1955; Fuller, 1956; Gerry, 1956; Wisman et al. 1958). These authors found that chicks fed diets supplemented better than controls, but not as well as those fed diets supplemented with fish meal. The objectives of the studies described here were to characterize some modern PBPM samples so that they could be included in diets balanced with respect, to their metabolizable energy, protein, and amino acid contents. Tests were then conducted to determine if chicks would grow better than expected based on the nutrient content of the PBPMs (Pesti et al. 1987; Escalona P. -m et al. 1987; Pesti and Escalona P., 1987). MATERIALS AND METHODS Samples were collected from three processing plants. Random samples during one week were obtained from continuous-flow plant A (#Is l-3). Monday morning (broiler waste only), Monday afternoon (broiler and hatchery wastes), and Friday afternoon (broiler and hatcher wastes and dissolved air floatation sludge) samples were obtained from continuous flow plant B ({j's 5-7). Sample #4 was obtained through commercial channels and was reported to be from plant B. A single sample (#.8) was obtained from batch processing plant C. Chemical analyses were by standard methods (Tables 1, 2 and 3). ME was estimated using a modification of Sibbald's procedure. Pepsin diggstibility in our laboratory was determined with.002x pepsin (Table 4). Available lysine was estimated by Carpenter's (1960) method. Multiple linear regression techniques were used to determine how well the chemical composition predicts ME n (Table 5). *Department of Poultry Science, University of Georgia, Athens, GA USA 175

2 TABLE 1 Poultry by-product meal sample compositions*

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5 ' TABLE 6 Influence of three poultry by-product meals fed at two levels in isoenergetic, isonitrogenous, corn and soybean meal based diets on the gain (g) and feed efficiency of male broiler chicks (Experiments 1 and 2)* PBPM sample Level (%) Gain' Effic? Gain Effic. Gain Effic. Experiment l$ Experiment k6 If5 5OOk t5 If #H k7 #5 518t # Orthogonal comparisons (significance probabilities) Basal vs. others Basal vs. 5% PBPM 5 vs. 10% PBPM PBPM #"5 vs. PBPM #7 Experiment 1 Experiment 2 Gain Effic. Gain --~~ Effic I66.OOl.llO,511 lgrams/20 days. Eight replicate pens of 10 male chicks each. 2Feed efficiency = gain/consumption x *From Escalona P. and Pesti,

6 Three samples of PBPM (#5, #7, #8) were incorporated at 50 or 100 g/kg levels in isoenergetic, isonitrogenous, corn and soybean meal based diets formulated with determined protein and ME contents. Each diet was fed to eight pens of ten male chicks each for 90 days (Table 6). RESULTS AND DISCUSSION The samples collected (Table 1) were similar to samples that are being fed by the broiler industry in the Southeastern U.S.A. (Table 2). Samples low in protein were high in calcium, etc., as would be expected. ME could be predicted fairly well from a number of measurements (Table 3)n The ash content of a sample was the best single predictor of ME accounting for approximately 79% of the variability. By knowing ash &d crude protein ME n could be predicted very well. The ME n of the "average" sample was somewhat higher than that listed in most ingredient composition tables. This may be due to changes in the composition and processing of the PBPM. The average sample has more dry matter, protein and ether 'extract than is listed in the NRC (1984) table, for instance. The earlier assays, upon which the table values are based, were conducted with PBPM substituted at the 40% level. Reduced estimates are expected at this level compared to lower levels (Pesti et e- al. 1987). The amino acid composition of the samples studied was similar to table values with the exception of tyrosine, which was much lower than expected (Table 4). Similar patterns in ranking of protein sources were found by the available lysine and pepsin digestibility methods. Samples from Plant A were the best, followed by the one from Plant C and then Plant B (Table 5). When samples of these poultry by-product meals were included at the 5% level in isoenergetic, isonitrogenous diets, no significant increases or decreases in gains or feed efficiency could be detected (Table 6). Earlier workers found better growth with diets containing low levels of PBPM than without (Romoser, 19855; Fuller, 1956; Gerry, 1956; Wisman, 1958). However, they made no effort to balance the protein, energy, amino acids, or minerals, as in these studies (Table 6). Chicks fed 10% PBPM did not gain as well as those fed 5%. The reason for this is not clear, since the protein, energy and minral contents of the diets were all the same, and essential amino acid minimums were the same in the formulations. It is interesting to note that chicks fed the diet containing sample #7 (Friday P.M.) did nearly as well as those fed #5 (Monday A.M.) (no significant difference, P =,309 for gain,.511 for efficiency). Sample #5 had a higher protein efficiency ratio and total and available lysine, but about the same pepsin digestibility. The reason for the apparent toxicity of PBPM when included at the 10% level is not clear. Since there is no known toxic factor in the PBPM, an amino acid or other imbalance may be involved. These data (Tables 1, 3-6) are hard to interpret in the light of previously published data since most research has been conducted with various mixtures of processed blood, offal and feathers (Naber et al. 1961; Jackson, 1971; Jackson and Fulton, 1971; Bhargava and 0'Nei.c l-5). PBPMs produced in 1985 were good products that can be fed at relatively low levels (at least 5%) and whose economic value should be based entirely on its nutrient content. 181