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ARS Home » Plains Area » Miles City, Montana » Livestock and Range Research Laboratory » Research » Publications at this Location » Publication #258839
Title: Small quantities of supplemental crude protein promote optimal neutral detergent fiber digestion and nitrogen retention in simulated dormant range forage diets

Author
item SAWYER, JASON - Texas A&M University
item MULLINIKS, JOHN - New Mexico State University
item Waterman, Richard
item Petersen, Mark

Submitted to: Rangeland Ecology and Management
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 4/1/2012
Publication Date: 7/1/2012
Citation: Sawyer, J.E., Mulliniks, J.T., Waterman, R.C., Petersen, M.K. 2012. Small quantities of supplemental crude protein promote optimal neutral detergent fiber digestion and nitrogen retention in simulated dormant range forage diets. Rangeland Ecology and Management. 90:2324-2330. https://doi.org/10.2527/jas.2011-4782.
DOI: https://doi.org/10.2527/jas.2011-4782

Interpretive Summary: Supplemental protein source may influence utilization efficiency. Ruminally DIP requirements are dependent on fermentability of the basal diet. When slowly fermented roughages are fed, lower amounts of DIP would be required and when excess degradable protein is fed, N losses from the rumen and decreased capacity to recycle N will likely occur. Protein sources higher in ruminally UIP may therefore improve utilization efficiency by slowly contributing to the ruminal N supply thus reducing potential ruminal N losses and enhancing N recycling. Lower quantities of a supplement that is higher in UIP may be utilized more efficiently than greater quantities of DIP when animals are consuming poor quality roughages with slower fermentation rates via mechanisms of improved NDF digestibility and minimized N losses.

Technical Abstract: Supplying minimal amounts of ruminally degradable protein from supplements may improve utilization efficiency when fed to ruminants grazing dormant forages. In Experiment 1, nitrogen retention was evaluated for 12 ruminally cannulated cows fed mature weeping lovegrass hay (Eragrostis curvula; 4.1% crude protein; 1.3 % body weight/d) and supplemented with different quantities of protein sources differing ruminal degradability. Cows were assigned to 1 of 3 sources of CP (urea; cottonseed meal, CSM; or 50% blood meal, 50% feather meal combination, BFM) fed to supply 0, 40, 80, or 160 g /d of CP. Fecal bags were utilized to obtain feces and urine. Ruminal fluid and serum samples were also collected. In Experiment 2, 4 ruminally cannulated steers were used in a 4×4 Latin Square to evaluate utilization of supplements differing in quantity and ruminal CP degradability. Steers were fed 6.8 kg/d chopped sudangrass hay (Sorghum bicolor) and supplemented with 56 g/d of a salt mineral mix (control); control + 28 g/d blood meal + 28 g/d feather meal (BFM); control + 98 g/d CSM (LCS); or control + 392 g/d CSM (HCS). Treatments provided 0, 40, 40, or 160 g/d of CP for control, BFM, LCS, and HCS; respectively. In Experiment 3, BFM was offered free choice to grazing cows for 60 d to determine acceptability and consumption rate. In Experiment 1, nitrogen retention with 40 g of CP from BFM was similar to 160 g of CP from CSM (P = 0.51). Ruminal NH3 and serum urea N concentrations were quadratic over time (P < 0.05) and increased linearly when increasing levels of UREA were fed (P < 0.05) but not when BFM or CSM were fed. In Experiment 2, supplementation increased ruminal DM disappearance (P < 0.10) although minimal differences were observed between BFM and LCS or HCS (P > 0.20). Ruminal NH3 concentrations were increased by supplementation (CON vs. supplements, P < 0.05). Lower quantities of supplemental CP were efficiently utilized.