Replacement of Corn Silage with Wheat Middlings and Calcium Chloride or Sodium Bicarbonate for Lactating Dairy Cows

¹ Department of Dairy Science, The Ohio State University, Columbus 43210

Five Holstein cows with ruminal cannulas were used in a 5 x 5 Latin square design in which one diet contained 50% corn silage (high forage control) and four diets contained 38 to 39% corn silage and 15% wheat middlings with or without addition of .45% CaCl₂ or .9% NaHCO₃ arranged in a 2 x 2 factorial. Diets averaged about 34% NDF. Addition of CaCl₂ to wheat middling diets generally doubled Ca concentration but decreased pH at 9 h postfeeding and decreased acetate:propionate ratio in the rumen; thus, milk fat decreased from 3.70 to 3.50%. The acidic effects of CaCl₂ appeared to negate any beneficial responses of increased Ca concentration. Because few interactions were noted for the combination of CaCl₂ and NaHCO₃, CaCl₂ would not likely be a more effective source of Ca than traditional sources. Cows fed wheat middling diets with NaHCO₃ had slightly higher ruminal acetate:propionate ratios, but milk fat percentage was unaffected compared with the ratios of cows fed wheat middling diets without NaHCO₃. Ruminal pH was below 6.0 for all treatments for at least 9 h postfeeding. Therefore, production of VFA probably exceeded buffering capacity for much of the feeding period and limited potential beneficial effects of addition of NaHCO₃ on fiber digestion and milk production. On average, cows fed wheat middling diets tended to have lower ruminal pH and acetate:propionate ratios but had higher DMI and FCM production than did those fed the high forage control diet. Results are interpreted to suggest that wheat middlings at 15% of DM are an effective substitute of corn silage for lactating cows.

Key Words: wheat middlings • calcium chloride • sodium bicarbonate • lactating cows

Submitted on August 10, 1992
Accepted on October 1, 1992