Interaction of replacing corn silage with soyhulls as a roughage source with or without 3% added wheat straw in the diet: Impacts on intake, digestibility and ruminal fermentation in steers fed high-concentrate diets

Authors: Neville, Bryan; PICKINPAUGH, WAYDE - North Dakota State University; MITTLEIDER, LEA - North Dakota State University; MOORE, REBECCA - North Dakota State University; SWANSON, KENDALL - North Dakota State University; CATON, JOEL - North Dakota State University

Submitted to: Translational Animal Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 5/16/2022
Publication Date: 5/17/2022
Citation: Neville, B.W., Pickinpaugh, W.J., Mittleider, L.J., Moore, R.L., Swanson, K.C., Caton, J.S. 2022. Interaction of replacing corn silage with soyhulls as a roughage source with or without 3% added wheat straw in the diet: Impacts on intake, digestibility and ruminal fermentation in steers fed high-concentrate diets. Translational Animal Science. 6(2). Article txac061. https://doi.org/10.1093/tas/txac061.
DOI: https://doi.org/10.1093/tas/txac061

Interpretive Summary: Feed resources continue to be one of the main expenses for beef operations. In years when roughage is in short supply due to drought the ability to utilize soyhulls instead of corn silage may prove beneficial for feedlot operations as long as feed intake, cattle performance, and ruminal fermentation are not adversely affected by soyhull inclusion as a roughage source. Soyhulls are currently not recommended for use as a roughage source in feedlot diets; however, soyhulls have been used as roughage sources in some research diets. The current study demonstrated the need for caution in utilizing soyhulls as a roughage source in high-concentrate feedlot diets due to decreased intake observed when soyhulls replaced corn silage. The decreased intake observed in this study would likely decrease feedlot cattle performance and underscores the need for additional research prior to recommending feeding soyhulls as a roughage source to cattle feeders.

Technical Abstract: Six ruminally cannulated steers [475.0 ± 49.6 kg initial body weight (BW)] were used in a 6 × 3 incomplete Latin square design (six treatments and three periods), to evaluate the impacts replacing of corn silage with pelleted soyhulls as roughage in high-concentrate finishing diets containing 30% modified distillers grains with solubles. Treatments were based on increasing dietary inclusion of soyhulls and consisted of: (1) Control (0), roughage supplied by dietary inclusion of 20% corn silage [dry matter (DM) basis]; (2) 50% replacement of corn silage with soyhulls (50); (3) 100% replacement of corn silage with soyhulls (100), and the same three treatments repeated with 3% added wheat straw (DM basis) replacing corn in the diet (0S, 50S, and 100S, respectively). Absolute dry matter intake (DMI; kg/d basis) tended to decrease both linearly and quadratically (P = 0.09) and proportional DMI (% of BW) decreased linearly (P = 0.04) with increasing soyhull inclusion but was not affected by the addition of straw in the diet (P = 0.68). Total tract digestibility of organic matter and crude protein were not affected by soyhull inclusion or added straw (P = 0.32). Ruminal pH did not differ (P = 0.65) with increasing soyhull inclusion but increased with the addition of straw (P < 0.01; 5.9 vs. 6.1 for no straw and straw, respectively). Molar proportions of acetate and butyrate decreased while propionate increased with increased soyhull inclusion (P <= 0.03; linearly and quadratically, respectively). Ruminal fluid kinetics were unaffected by either rate of replacement of corn silage with soyhulls or wheat straw inclusion (P <= 0.13). Decreases in DMI observed in this study would likely decrease finishing cattle performance and underscores the need for additional research before recommending this practice to cattle feeders.