Protein and Amino Acid Quality of Feather Meals

Abstract

Experiments were conducted to evaluate protein quality and TMEn of seven commercial feather meal (FM) samples by various in vivo and in vitro methods. True digestibilities of amino acids (AA) were determined with a 48-h excreta collection assay using conventional (CONV) and cecectomized (CEC) cockerels. Bioavailabilities of Lys and TSAA were estimated by chick growth assays using purified crystalline AA diets. Protein efficiency ration (PER; grams of gain:grams of CP consumed) was determined by feeding chick diets containing 9% CP supplied solely by a FM. The FM samples averaged (range) 81.0% (76 to 87) CP, 1.82% (1.46 to 2.15) Lys, 4.79% (4.07 to 5.30) Cys, .52% (.45 to .61%) Met, and 1.20% (.93 to 1.66) lanthionine. The PER values averaged .97 (.80 to 1.22). Pepsin N digestibility values determined with .2% pepsin ranged from 70 to 81%, whereas those determined with .002% pepsin ranged from 17 to 49%. True digestibilities of several AA were lower for CEC than for CONV birds. Chick Lys bioavailability values were much lower than the corresponding digestible Lys values for most FM, varied greatly among individual FM samples, and also varied markedly depending on method of calculation. The chick growth assays yielded imprecise estimates of bioavailability of Lys and Met in FM.Correlation analyses indicated that lanthionine concentration was negatively correlated with most in vitro and in vivo assay values. The .002% pepsin digestibility values were more highly correlated with in vivo assay values than were the .2% pepsin ones. Digestible Lys and Cys values for CEC and CONV birds were highly correlated with one another and were also highly correlated with bioavailable Lys and TSAA values, respectively. Mean TMEn was 3.471 kcal/g of DM (2.804 to 3.931) for CEC cockerels and 3.799 kcal/g of DM (3.263 to 4.381) for CONV cockerels, and me values were highly correlated (r = .95).