Ruminal degradability of dry matter, crude protein, and amino acids in soybean meal, canola meal, corn, and wheat dried distillers grains

• Published in: Journal of dairy science Vol. 96; no. 8; pp. 5151 - 5160
• Main Authors: Maxin, G., Ouellet, D.R., Lapierre, H.
• Format: Journal Article
• Language: English
• Published: United States Elsevier Inc 01.08.2013; American Dairy Science Association
• Subjects: amino acid; amino acids; Amino Acids - metabolism; Animal Feed; Animals; bags; Brassica napus - metabolism; canola meal; Cattle - metabolism; Cattle - physiology; corn; cows; crude protein; Dietary Proteins - metabolism; Digestion - physiology; distillers grains; Edible Grain - metabolism; Female; Glycine max - metabolism; grass hay; Holstein; lactation; Life Sciences; nylon; protein; protein sources; protein supplement; protein supplements; rumen; Rumen - physiology; rumen degradation; soybean meal; Triticum - metabolism; wheat; Zea mays - metabolism; rumen degradation; protein supplement; amino acid; protein; BARLEY SILAGE; MILK-PRODUCTION; PLUS SOLUBLES; INTESTINAL DIGESTIBILITY; LACTATING DAIRY-COWS; CATTLE DIETS; NITROGEN; DEGRADATION; RUMEN DEGRADABILITY; IN-SITU
• ISSN: 0022-0302; 1525-3198
• DOI: 10.3168/jds.2012-6392

Different protein sources, such as canola meal (CM) or dried distillers grains (DDG), are currently used in dairy rations to replace soybean meal (SBM). However, little data exists comparing their rumen degradation in a single study. Therefore, the objective of this study was to compare the ruminal degradation of dry matter (DM), crude protein (CP), and AA of SBM, CM, high-protein corn DDG (HPDDG), and wheat DDG plus solubles (WDDGS). In situ studies were conducted with 4 rumen-fistulated lactating Holstein cows fed a diet containing 38% grass hay and 62% corn-based concentrate. Each protein source was incubated in the rumen of each cow in nylon bags for 0, 2, 4, 8, 16, 24, and 48h to determine DM and CP rumen degradation kinetics, whereas additional bags were also incubated for 16h to evaluate AA ruminal disappearance. Rumen DM and CP degradability was calculated from rumen-undegraded residues corrected or not for small particle loss. Data were fitted to an exponential model to estimate degradation parameters and effective degradability (ED) was calculated with a passage rate of 0.074h−1. The WDDGS and SBM had higher uncorrected ED (DM=75.0 and 72.6%; CP=84.8 and 66.0%, respectively) than CM and HPDDG (DM=57.2 and 55.5%; CP=59.3 and 48.2%, respectively), due to higher soluble fraction in WDDGS and a combination of higher potentially degradable fraction and rate of degradation in SBM. Correction for small particle loss from bags, higher for WDDGS than for the other protein sources, decreased estimated ED but did not alter feed ranking. The ruminal disappearance of AA after 16h of incubation reflected the overall pattern of CP degradation between protein supplements, but the ruminal disappearance of individual AA differed between protein supplements. Overall, these results indicate that, in the current study, (1) SBM and WDDGS were more degradable in the rumen than CM and HPDDG, and (2) that small particle loss correction is relevant but does not alter this ranking.