The effect of sodium benzoate on the nutritive value of rehydrated sorghum grain silage for dairy cows.

• Sodium benzoate increases aerobic stability of rehydrated sorghum grain silage (RSGS). • Proteolysis reduced in RSGS treated with sodium benzoate. • Acetate to propionate ratio was higher when cows were fed RSGS treated with sodium benzoate. • Feeding RSGS treated with sodium benzoate did not alter the performance of dairy cows. The objective of this trial was to evaluate the nutritional value of rehydrated sorghum grain silage treated with sodium benzoate, for use in dairy cow feed. Fifteen-hundred kg of dry ground sorghum were rehydrated to 350 g/kg moisture and ensiled in 200-L plastic drums. At ensiling, grain was either treated with sodium benzoate at 2 g/kg as fed (Benzoate) or nothing (Control). Twelve mid-lactating Holstein cows, with 170 ± 47 d in milk, received a standard diet for 14 d, and then were paired blocked and assigned to one of two dietary treatments for 28 d. Diets contained (dry matter basis): 360 g/kg corn silage, 48 g/kg Tifton haylage, 122 g/kg whole cottonseed, 184 g/kg soybean meal, 27 g/kg mineral-vitamin premix, and 258 g/kg rehydrated sorghum grain silage (Control or Benzoate). Dry matter intake, milk yield and composition were measured weekly, whereas rumen fermentation profile and feeding behavior were measured the last week of the experimental period. Silages treated with sodium benzoate had lower concentrations of ethanol (P = 0.05), ethyl-esters (P < 0.05) and soluble protein (P =0.02), and less yeast counts (P < 0.01). Therefore, silage treated with benzoate had higher aerobic stability compared to control silages (P < 0.01). Ruminal acetate to propionate ratio was lower in cows fed the control treatment compared to benzoate (2.66 vs. 2.96), due to the greater proportion of propionate in the rumen fluid (19.0 vs. 17.8 mol/100 mol of volatile fatty acids). However, dry matter intake, milk yield and composition did not differ between treatments. Sodium benzoate changed silo and rumen fermentation profile without altering the performance of mid-lactation dairy cows. [ABSTRACT FROM AUTHOR]