PSI-26 - Comparison of whole cottonseed to a traditional supplement (20% breeder cubes) in commercial beef cows: impacts on estimated forage intake, metabolites, and methane emissions

Abstract: The objective was to compare whole cottonseed (WCS) to a more traditional supplement (20% breeder cube; BC) to determine the impacts on estimated forage intake, metabolites, and methane emissions in beef cows. Cows (n = 24) were assigned to 1 of 2 experimental treatments (BC vs. WCS) based on age and body weight (BW). Supplements were fed individually at 0.9, 1.8, or 2.7 kg per d, resulting in 12 animals per supplement treatment and 4 animals per supplementation level within treatment. Two additional cows served as negative controls. Cows were fed 4 d per wk, with supplementation levels being prorated at 1.6, 3.2, and 4.8 kg per feeding. Data collection occurred in 28 d intervals through d 84, with a final collection on d 99 after all cows had calved. Forage intake was estimated by dosing all animals once daily with a 10 g TiO2 bolus for 13 consecutive d. Fecal samples were obtained on d 11-14 in respect to TiO2 bolus administration. There were no interactions observed (P = 0.37), no effect of treatment (P = 0.31), and no effect of amount fed per d (P = 0.20) on estimated forage dry matter intake (DMI). A treatment × amount fed per d × d interaction for plasma glucose concentrations (P = 0.04) was detected. An amount fed per d × d interaction was detected for plasma lactate concentrations (P = 0.01) indicating that cattle receiving different amounts of supplement had different trends in lactate concentrations over time. An effect of amount fed per d on plasma lactate concentrations (P = 0.05) was also observed, where lactate concentrations increased with increasing supplementation, excluding cows receiving no supplementation. A tendency for an amount fed per d × d interaction for plasma urea nitrogen (PUN; P = 0.06) was observed indicating that cattle receiving different amounts of supplement had varying trends in PUN over time. While there were no interactions detected for non-esterified fatty acid concentrations (NEFA; P ≥ 0.22) nor an effect of treatment (P = 0.91), there was a day effect detected (P = 0.0005). There was a treatment × amount fed per d × d interaction for plasma gossypol concentrations (P = 0.001). There was also a tendency for treatment × amount fed per d interaction observed (P = 0.09), but no effect of treatment (P = 0.79). No treatment effect on methane emissions was observed between cows consuming BC and WCS (P = 0.68). This experiment suggests that the supplementation of BC or WCS had minimal impacts on estimated forage DMI, metabolites, or methane emissions, but some interactions existed between supplementation source or level and d.