Location: Livestock, Forage and Pasture Management Research Unit
Project Number: 3070-31630-008-009-S
Project Type: Non-Assistance Cooperative Agreement
Start Date: Jul 15, 2025
End Date: Jul 14, 2027
Objective:
Determine how cashew nut-shell liquid impacts the energetic efficiency, ruminal fermentation patterns, growth performance, and carcass characteristics of finishing beef steers.
Approach:
Sixty-four steers will be fed a finishing diet (95 Mcal of net energy of maintenance per 100 lb of diet dry matter) and assigned to one of four treatments arranged in a 2×2 factorial design. These treatments will be either: 1) control, diet with no monensin or cashew nut-shell liquid (CNSL); 2) a diet containing monensin to supply approximately 330 mg per head per day; 3) a diet containing CNSL at 1% of dietary dry matter inclusion; or 4) a diet providing both monensin and CNSL. Steers will be fed their respective treatment diets until they achieve acceptable harvest weights (1,450 lb of body weight), approximately 150 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 75); and end (d 150) 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, and starch content. 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. Indigestible acid detergent of diet and feces will be used to estimate diet digestibility. Further, the nutrient concentration of feces and diets together with indigestible acid detergent fiber 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. This information will be used to calculate the feed energy lost as heat production.