Cotton burrs as alternative roughage to adapt beef steers to steam-flaked corn-based finisher diet

Abstract Text:

Effect of cotton burrs as a roughage source during the transition of beef cattle (hay to finisher diet) was evaluated on intake, ruminal characteristics, nutrient digestibility, and feeding behavior. Ruminally cannulated steers (n = 6; BW = 235 ± 81 kg) were assigned using a complete randomized design to 1 of 2 adaptation strategies: Alfalfa hay-based or cotton burrs-based. In both strategies, roughage sources decreased as steam-flaked corn gradually increased. Steers were fed ad libitum once daily, a series of six diets (7-d period each): wheat hay; 4 step-ups; and a finisher. In situ technique was used to assess ruminal fiber degradability (substrate = wheat hay). Wireless rumen pH probes were used. A 3-d spot fecal collection (twice daily, last 3 d of each period) and AIA were used to estimate total tract apparent nutrient digestibility. Rumen fluid samples (0, 4, 8, and 16 h post-feeding) were taken (d-6 of each period) for VFA and NH₃. Data were analyzed using Glimmix procedure of SAS (wheat hay period used as a covariate). Intake was not affected by adaptation strategies (P ≥ 0.16), except for a tendency (P = 0.10) for steers adapted with alfalfa-strategy to ruminate more per kg of NDF consumed during finisher diet, than those adapted with cotton burrs-strategy. Steers fed cotton burrs-strategy showed lower ruminal pH average on step-3 and finisher periods (5.62 and 5.51 vs. 6.04 and 5.83; P < 0.01 and P = 0.05, respectively) compared with alfalfa-strategy. A greater area of pH below 5.6 (200 vs. 15 min*pH; P < 0.01); lower ruminal NH₃ concentration (5.1 vs. 8.8 mg/L; P < 0.01); and lower digestibility (OM, ADF, and hemicellulose; P ≤ 0.02) during step-3 were also observed for steers fed cotton burrs-strategy compared to alfalfa-strategy, respectively. However, cotton burrs-strategy steers showed greater (P = 0.01) NDF digestibility during step-4; greater (P < 0.01) OM digestibility during finisher diet; and lower acetate/propionate ratio (P = 0.04) with a tendency (P = 0.08) to have greater propionate molar proportion during step-2, compared to alfalfa-strategy steers. Ruminal fiber degradability was not affected by adaptation strategies (P ≥ 0.36), neither was dietary starch digestibility during common finisher (P = 0.73). Cotton burrs adaptation strategy induced an improved ruminal fermentation environment during finisher diet, although with riskier ruminal pH and rumination than alfalfa-strategy. Further evaluation must consider cattle growth performance and economic aspects.

Keywords: adaptation, cotton burrs, alfalfa