In situ ruminal crude protein degradability of by-products from cereals, oilseeds and animal origin

The aim of this study was to establish a database on in situ ruminal crude protein (CP) degradability characteristics of by-products from cereal grains, oilseeds and animal origin commonly fed to ruminants in Pakistan and South Asian Countries. The oilseed by-products were soybean meal, sunflower meal, mustard seed meal, cottonseed meal, decorticated and un-decorticated cottonseed cake, maize oil cake and mustard seed cake. The cereal grain by-products were corn gluten meal, corn gluten feed, guar meal, toria meal, rice meal, rice polishings, rice bran and wheat bran. The animal by-products were fish meal, feather meal, blood meal, and meat and bone meal. Four samples per feed were collected from different dairy farms (n=1), local markets (n=1), and agro-food industries (n=2). Ruminal protein degradation characteristics of the feeds were determined using the in situ nylon bag technique where each feed was incubated in the rumen of 3 mature steers for 2, 4, 8, 12, 24 and 48 h. There were large differences in instantly soluble (W) fraction, potentially rumen degradable (D) fraction, rate of degradation (kd) and effective degradability of crude protein (EDCP) among the by-product feeds. Among the oilseed by-products, mustard seed cake had the highest (P<0.05) and un-decorticated cottonseed cake had the lowest EDCP values at the three outflow rates (0.02, 0.05 and 0.08/h). Similarly, among cereal grain by-products wheat bran had the highest (P<0.05) and rice bran had the lowest EDCP. The animal by-product based protein feeds had lower kd and EDCP values compared to oilseeds and cereal grain by-product based protein feeds, and can be used to increase the bypass protein. The CP degradation parameters reported in this study can be used to optimize diet formulation for ruminant livestock in terms of protein supply to the animals, and reduce N losses to the environment and increase economic profitability of the dairy farmers.