Evaluation of the In Situ Degradation Kinetics of Some Protein Sources Commonly Used in Ruminant Feeding


Abstract: The aim of the study was to evaluate the in situ degradation kinetics of some commonly used protein sources (sunflower meal, cottonseed meal, and soybean meal). Three ruminally fistulated rams were utilized in the study. They were fed ground alfalfa and a mixture of concentrate (60% alfalfa and 40% mixture) at maintenance level. The Dacron bags used in the study had a 45 µ^2 pore size and internal dimensions of 15 x 7 cm. Feed samples were ground to pass through a 2 mm screen. Samples were incubated in the rumen of rams for 0, 2, 4, 8, 12, 24 and 48 h. Each feed sample was incubated in the rumen of 3 rams in duplicate for each incubation time. Approximately 3.5 g of samples were placed in each Dacron bag. Concentrations of organic matter were 93.16%, 94.43% and 93.40% (P < 0.05); ether extract 1.70%, 7.12% and 2.79% (P < 0.05); crude fiber 21.64%, 19.81% and 6.77% (P < 0.05); crude protein 32.03%, 30.07% and 50.02% (P < 0.05); and ADIN-N 11.57%, 11.00% and 10.45% (P < 0.05) for sunflower meal (SFM), cottonseed meal (CSM) and soybean meal (SBM), respectively. Ruminal DM degradability of samples was highest with SBM for all incubation times followed by SFM and CSM in that order (P < 0.05). While crude protein degradabilities of SFM were significantly higher (P < 0.05) than those of CSM and SBM up to 12 h incubation, they were significantly higher (P < 0.05) than those of CSM but similar to those of SBM at 24 and 48 h incubation times. Crude protein degradabilities were 55.72%, 41.08% and 66.06% after 8 h incubation for SFM, CSM and SBM, respectively (P < 0.05). Concentrations of water soluble protein were 45.93%, 37.65% and 35.79% (P < 0.05); potentially degradable protein 44.21% , 29.48% and 55.72% (P < 0.05); non-degradable protein 9.86%, 32.87% and 8.49% (P < 0.05); k, h^{-1} were 0.173, 0.066 and 0.114 (P < 0.05); percentages of escape protein were 18.41%, 42.50% and 33.55% (P < 0.05); and escape protein 57.90, 130.30 and 167.80 g/kg (P < 0.05) for SFM, CSM and SBM, respectively. In conclusion, the concentration of water soluble protein was highest with SFM, potentially degradable protein content was highest with SBM, and non-degradable protein concentration was highest with CSM among the 3 protein sources. However, the highest escape protein concentration was obtained (167.8 g/kg) with SBM.

Keywords: Sunflower meal, cottonseed meal, soybean meal, degradation kinetics, escape protein

Full Text: PDF