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ARS Home » Plains Area » Bushland, Texas » Conservation and Production Research Laboratory » Livestock Nutrient Management Research » Research » Publications at this Location » Publication #402513
Research Project: Strategies to Manage Feed Nutrients, Reduce Gas Emissions, and Promote Soil Health for Beef and Dairy Cattle Production Systems of the Southern Great Plains

Location: Livestock Nutrient Management Research

Title: Evaluation of site and extent of protein digestion of feedstuffs commonly fed in Southern Plains finishing diets

Author
item PROCTOR, JARRET - Texas A&M University
item Beck, Matthew
item KASUSKE, ZACHARY - Former ARS Employee
item FOSTER, RYAN - Texas A&M University
item LONG, NATHAN - Texas A&M University
item WICKERSHAM, TRYON - Texas A&M University
item GOUVÊA, VINICIUS - Texas Agrilife
item SMITH, JASON - Texas Agrilife Extension

Submitted to: Meeting Abstract
Publication Type: Abstract Only
Publication Acceptance Date: 3/8/2023
Publication Date: 4/7/2023
Citation: Proctor, J.A., Beck, M.R., Kasuske, Z.A., Foster, R.C., Long, N.S., Wickersham, T.A., Gouvêa, V.N., Smith, J.K. 2023. Evaluation of site and extent of protein digestion of feedstuffs commonly fed in Southern Plains finishing diets [abstract]. Plains Nutrition Council. p. 115.

Interpretive Summary:

Technical Abstract: Meeting metabolizable protein requirements of finishing cattle without overfeeding protein requires reliable estimates of site and extent of protein digestion. Current estimates of rumen degradable (RDP) and undegradable protein (RUP), as well as intestinal digestibility of RUP (dRUP) may be inadequate. Thus, the objectives of this experiment were to quantify RDP, RUP, and dRUP of common feedstuffs and evaluate nutrient composition as a predictor of RDP, RUP, and dRUP. Ruminally cannulated steers (n = 6; initial BW = 1662 ± 44.1 lbs) consuming a finishing diet were enrolled in a replicated 3 × 3 Latin square design. Within period, steers were assigned a feedstuff classification for in situ ruminal incubation. Feedstuff classifications were grain (steam-flaked and whole-shelled corn, wheat, and milo), protein (wet and dried corn distiller’s grains, Sweet Bran, cottonseed meal, canola meal, and soybean meal), and roughage (cotton burrs, alfalfa hay, wheat hay, sorghum × sudangrass hay, wheat silage, and corn stalks). Feedstuffs were lyophilized, ground through a 2-mm screen, aliquoted into in situ bags, and ruminally incubated for 0, 4, 8, 12, 24, or 48 h. Samples were composited within incubation time point, analyzed for crude protein (CP), corrected for microbial contamination, and fit to non-linear models to estimate RDP and RUP using calculated passage rate. Subsamples of in situ digested feedstuffs were aliquoted into filter bags for in vitro pepsin-pancreatin digestion and CP analysis to estimate dRUP. Statistical analyses were conducted using JMP Pro 16.0 and R (v4.1.0). On average, RUP estimates were 37.0% lower (P < 0.05) for protein ingredients, yet grains and roughages were not different (P > 0.73) compared to NASEM (2016) values, respectively. However, dRUP was, on average, 11.9% and 33.1% lower (P < 0.01) for protein ingredients and roughages, yet grain dRUP was not different (P = 0.16) when compared to NASEM (2016) values, respectively. Neutral detergent fiber (NDF) and CP explained a substantial portion of the variation in RDP (P < 0.01, R2 = 0.94, RMSE = 2.26). Additionally, acid detergent fiber, NDF, and CP explained the majority of the variation in dRUP (P < 0.01, R2 = 0.91, RMSE = 5.43). Collectively, these data suggest that dRUP values of protein ingredients and roughages are lower than recommendations by the NASEM (2016). Furthermore, CP and fiber values may be capable of predicting RDP, RUP, and dRUP, but require further validation.