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Determination of nitrogen balance in goats fed a meal produced from hydrolyzed spent hen hard tissues

S. R. Freeman^*, M. H. Poore^*, G. B. Huntington^*, T. F. Middleton and P. R. Ferket

^* Animal Science Department, North Carolina State University, Raleigh, NC 27695 , Ag ProVision, LLC, Kenansville, NC Poultry Science Department, North Carolina State University, Raleigh, NC

Sharon_Freeman{at}ncsu.edu

Abstract

In order to provide an economically viable and environmentally sound method for disposing of spent laying hens, we manufactured a proteinaceous meal from the hard tissue fraction of mechanically deboned laying hens (primarily feathers, bones, and connective tissue). We hydrolyzed the hard tissue and co-extruded it with soybean hulls to create a novel feather and bone meal (FBM) containing 94.2% DM, 23.1% CP, 54.5% NDF, and 7.3% fat (DM basis). We evaluated the FBM in supplements for meat goats in which it provided 0, 20, 40, or 60% of the N added to the supplement vs. a negative control supplement with no added N source. The remainder of the N was contributed by soybean meal (SBM). Supplementation of N resulted in greater DMI than the negative control (P = 0.005) and DMI changed quadratically (P = 0.11) as FBM increased in the supplement. Digestibility of DM was similar in all diets, including the negative control (P > 0.10). Fiber digestibility increased linearly as dietary inclusion of FBM increased (P = 0.04 for NDF, P = 0.05 for ADF), probably as a result of the soybean hulls in the FBM. Nitrogen digestibility declined linearly from 60.5% with 0% FBM to 55.6% with 60% FBM (P = 0.07), but N retention changed by a quadratic function as FBM replaced SBM (P = 0.06). Negative control goats had lower N digestibility (P < 0.001) and N retention (P = 0.008) than the N-supplemented goats. Feather and bone meal had a greater proportion of ruminally undegradable B₃ protein than SBM (23.1 vs. 0.3% of CP, respectively). Ruminal VFA and pH were unaffected by replacing SBM with FBM, but supplying no source of N in the concentrate resulted in reduced total VFA in ruminal fluid (P = 0.04). Ruminal ammonia level increased quadratically (P = 0.07) as FBM increased, reflecting increased intake, and it was much lower in unsupplemented goats (P < 0.001). Serum urea had less variation between 0 and 4 h after feeding in goats receiving 40 or 60% of added N as FBM in comparison to those receiving only SBM or 20% FBM. Feather and bone meal promoted a more stable rumen environment, possibly due to reduced rates of protein degradation within the rumen. A palatable byproduct meal for ruminants can be made from spent laying hen hard tissue, one that supports similar N metabolism to traditional protein sources.

Key Words: byproducts • meat goats • nitrogen balance • spent laying hens