Variation in ruminai degradation and intestinal digestion of animal byproduct proteins

In situ and in vitro procedures were used to determine ruminai degradation and intestinal digestion of crude protein (CP) from animal byproducts. Seven samples of meat and bone meal (MBM), hydrolyzed feather meal (HFM), ring dried blood meal (RBM), and batch dried blood meal (BBM) were obtained from various rendering and meat packing plants. Ruminal undegradable CP determined using in situ procedures ranged from 51.3 to 60.8% (x̄ = 55.4 ± 1.3%), 53.6-87.9% (x̄ = 73.6 ± 3.8%), 76.4-86.4% (x̄ = 81.0 ± 1.2%), and 77.6-94.4% (x̄ =84.3± 2.1%), for MBM, HFM, RBM and BBM, respectively. Estimates of intestinal digestion of ruminai undegradable CP, determined using a three-step in vitro procedure, ranged from 40.9 to 70.1% (x̄ = 56.0 ± 4.0%), 59.2-75.2% (x̄ = 65.3 ± 2.1%), 72.0-90.3% (x̄ = 79.6 ± 2.5%) and 28.8-79.2% (x̄ = 61.4 ± 6.8%), for MBM, HFM, RBM, and BBM, respectively. Total intestinally absorbable dietary protein (IADP) was calculated as ruminai undegradable protein multiplied by intestinal digestion of the ruminal undegradable protein fraction. Intestinally absorbable dietary protein ranged from 21.6 to 39.3% (x̄ = 31.2 ± 2.7%), 35.8-59.4% (x̄ = 47.6 ± 3.1%), 57.5-75.2% (x̄ = 64.6 ± 2.6%), and 24.8-62.7% (x̄ = 51.3 ± 5.3%), for MBM, HFM, RBM, and BBM, respectively. Results demonstrate that large variations in ruminai degradation, intestinal digestion and IADP can occur among and within different rendering byproducts. These variations should be considered when determining the quality of animal byproducts as protein supplements for ruminants. Measurements of ruminai degradation and intestinal digestion of CP should be used by manufacturers to guarantee the quality of various batches of byproduct that are produced.