The in vivo protein quality of 14 meat and bone meals (MBM) was evaluated in three chick growth assays and a 48-h excreta collection assay using conventional and cecectomized roosters. In addition, in vitro evaluation of protein quality was assessed using pepsin N digestibility (0.2, 0.002, or 0.0002% pepsin), KOH protein solubility, and multi-enzyme pH change. Crude protein, lysine, and SAA in the MBM varied from 48 to 56, 2.32 to 3.01, and 1.0 to 2.13%, respectively. Protein efficiency ratio (weight gain:protein intake) estimated from feeding chicks diets containing 9% protein from a MBM ranged from 0.61 to 2.89 and averaged 1.78. Lysine bioavailability determined by slope-ratio chick assay ranged from 43 to 89%. True amino acid digestibility and TMEn values determined in cecectomized roosters were generally lower (P < 0.05) than those determined in conventional roosters. True digestibility of amino acids (percentage) also varied among MBM, with the mean (and range) for lysine, methionine, and cystine in cecectomized birds being 81 (73 to 88), 85 (77 to 91), and 58% (37 to 72%), respectively. Pepsin N digestibility values determined using 0.002 or 0.0002% pepsin were positively correlated (P < 0.05) with lysine digestibility. Pepsin N digestibility determined using 0.2% pepsin, KOH protein solubility, and multi-enzyme pH change were not significantly correlated with in vivo protein quality. Ash content was negatively correlated (-0.80, P < 0.05) with protein efficiency ratio. These results indicated that there is substantial variation in protein quality among commercial MBM and that pepsin N digestibility and ash content are correlated with some in vivo protein quality measurements.
Intestinal absorption of crystalline DL-methionine (DL-MET) and DL-methionine hydroxy analog calcium (DL-HMA) were determined in a true-digestibility-balance assay using cecectomized (CEC) and sham-operated conventional (CONV) cockerels. The treatments consisted of fasted birds and birds crop-intubated (CI) with 30 g of a corn-soybean meal basal diet (16% CP) supplemented with 0, .2, or .4% of DL-MET or equimolar levels of DL-HMA. There was no detectable free D-MET or L-MET or HMA in the excreta of fasted birds or of those fed the unsupplemented basal diet. The intestinal absorption of DL-HMA was 95.9 +/- .8% (means +/- SE) for CEC and 98.8 +/- .8% for the CONV cockerels. The absorption of DL-MET was approximately 99.7 +/- .2% for the CEC and the CONV cockerels. In a second experiment procedures were developed for a bioavailability assessment by comparing the growth responses to CI and intraperitoneal-injected (IP) DL-MET or DL-HMA in chicks fed a crystalline-amino-acid diet deficient in methionine. Graded increments of pH-adjusted DL-MET or DL-HMA (in water solutions) were administered twice daily in a 7-day growth assay. Slope-ratio analysis indicated that bioavailability (+/- SE) of CI DL-HMA was 91.3 +/- 11.8% relative to the CI DL-MET on an equimolar basis. The bioavailability of CI DL-HMA was similar to that of IP DL-HMA, indicating that the intestinal absorption of DL-HMA was highly efficient.(ABSTRACT TRUNCATED AT 250 WORDS)
Three experiments were conducted to determine the order of amino acid (AA) limitation in meat and bone meal (MBM) using AA addition and deletion assays. In two addition assays, various individual and combined additions of eight AA were made to semipurified basal diets containing 16% protein solely from a MBM. The two MBM had previously been determined to vary greatly in protein quality. In the deletion assay, a semipurified basal diet containing 13.5% CP provided solely by MBM was supplemented with L-Thr, L-Val, DL-Met, L-Leu, L-Ile, L-Phe, L-Tyr, L-Lys-HCl, L-His, and L-Trp to fulfill the Illinois Ideal Protein or AA pattern on a digestible basis. Each AA was then deleted individually from the basal diet, and the effect of its deletion on growth performance was assessed. In both addition assays, supplementation of the MBM basal diet with Trp and Cys together yielded a large increase in growth performance, whereas supplementation with these AA individually had no effect. These results indicated that Trp and sulfur AA (with a primary need for Cys) were equally first limiting in the MBM. The order of limitation for the other AA was unclear. The results of the deletion assay showed that deletion of Trp, Thr, Phe + Tyr, Ile, Met, Lys, Val, or His significantly depressed growth performance. The results of the combined addition and deletion experiments indicated that the order of AA limitation in MBM was 1) Trp and sulfur AA, 2) Thr, 3) Ile and Phe + Tyr, 4) Met, 5) Lys, and 6) Val and His. The deletion assay using diets formulated on an ideal protein basis was more effective than the addition assay for determining the order of AA limitation in MBM.
The use of corn gluten feed (CGF) in the diets of laying hens and in induced molting programs was investigated through four experiments. The first two experiments evaluated the effects of CGF on egg production from 23 to 56 or from 32 to 65 wk of age. Graded levels of CGF from 0 to 25% were added to a corn-soybean meal, control diet (16.5% CP) in a nonisocaloric and an isocaloric manner. The ratio for dietary MEn:protein was held constant in some diets, but varied in others. The nonisocaloric inclusion of up to 25% CGF did not negatively affect egg production in either experiment. When 25% CGF was fed to the 32 wk old hens, egg weight was decreased. Egg weight was also decreased when 10% CGF or higher levels were fed to the younger hens. The nonisocaloric addition of CGF also increased feed intake and decreased feed efficiency (gram of egg per gram of feed) in most cases. Isocaloric inclusion of 15% CGF did not affect egg-production parameters, but 25% CGF negatively affected most parameters. When the ratio for MEn:protein of the CGF diets was equal to that of the control diet, 25% CGF negatively affected most parameters, 17.5% CGF decreased egg weight and feed efficiency, and 10% CGF increased egg production. Feed intake was increased at all of the CGF levels. Two additional experiments evaluated CGF in programs for induced molting. The molting procedure involved feed withdrawal for 10 days followed by feeding molt diets consisting of 99.75% corn, 99.75% CGF, 49.75% corn:50% CGF, or two grower-type diets for pullets (15% CP) containing 25% CGF or 18.5% wheat bran. The two grower-type diets for pullets yielded similar and significantly greater postmolt gains in body weight and early postmolt egg production (3 wk) than did the other diets. The corn:CGF diet also yielded greater postmolt weight gains and early postmolt egg production than the 100% corn or 100% CGF diets. Long-term postmolt egg production (30 or 37 wk) was not affected by the molt diets.
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