Location: Livestock, Forage and Pasture Management Research Unit
Project Number: 3070-31630-008-008-S
Project Type: Non-Assistance Cooperative Agreement
Start Date: Jul 15, 2025
End Date: Jul 14, 2027
Objective:
Determine how roughage levels in feedlot diets impacts the energetic efficiency, ruminal fermentation and growth performance of beef steers.
Approach:
16 steers will be fed high-concentrate diets and assigned to one of four treatments arranged in a completely random design. These treatments will be either: 4 evenly spaced roughage levels from 65 to 90%. Steers will be fed their respective treatment diets for approximately 90 days. Steers will be fed daily in a feed intake measurement system and will be weighed weekly to assess average daily gain. Ruminal fluid, fecal, and blood samples will be collected at the beginning (d 0); middle (d 45); and end (d 90) of the feeding period. Ruminal samples will be analyzed for ruminal microbiome composition using 16S amplicon sequencing; volatile fatty acid concentrations by gas chromatography; and ammonia concentrations using a colorimetric procedure. Fecal samples will be analyzed for neutral and acid detergent fiber, crude protein, fecal energy, starch content, and acid-insoluble ash. Diet samples will be collected weekly and composited by weight into four samples from each diet. Diet samples will be analyzed for proximate analysis, gross energy by bomb calorimetry, starch using a colorimetric procedure, and indigestible acid-detergent fiber. Acid-insoluble ash of diet and feces will be used to estimate diet digestibility. Further, the nutrient concentration of feces and diets together with acid-insoluble ash will be used to calculate fiber, crude protein, and starch digestibility, and digestible energy content of the diets. Finally, oxygen consumption, methane and carbon dioxide emissions will be measured using an automated head chamber system and this information will be used to calculate the feed energy lost as heat production.