Effect of Prepartum Dietary Carbohydrate Source on Feed Intake, Energy Balance, Rumen Fermentation, and Milk Yield and Components of Holstein Cows

Sixty eight Holstein cows, 38 primiparous and 30 multiparous ones, were employed in a randomized complete block design, blocked to evaluate the effects of 2 diets in various ruminal fermentable carbohydrate sources (Ground Corn vs Rolled Wheat) on rumen fermentation and performance during preparturient period. Primiparous and multiparous cows were blocked by parity. The cows were fed diets as total mixed ration with similar energy and crude protein content including 1) 18.57% GC; 2) 18.57% RW from -23.1 ± 9 d relative to expected calving until calving. Followeing calving, all the animals received the same lactation diet for 28 days. The results revealed that, dry matter intake, energy intake, energy balance, and body condition score did not differ between multiparous cows fed either the ground corn or rolled wheat diet at preparturient period. Dry matter intake, energy intake, and energy balance were lower for primiparous cows fed the rolled wheat diet at prepartum period (p<0.05) with no differences observed after calving. Higher ruminal propionate was produced through feeding the rolled wheat diet to multiparous cows at prepartum. Acetate to propionate ratio was also lower for these cows (p<0.05). There were no significant differences observed between multiparous cows for milk yield and its components with the exception of milk urea nitrogen. Primiparous cows fed with the rolled wheat diet had a greater milk protein content and yield (p<0.05) relative to cows fed the ground corn diet. Milk urea nitrogen was lower for multiparous and primiparous cows fed the rolled wheat diet (p<0.05). In total, it can be concluded that, feeding prepartum diets containing rapidly fermentable sources of starch (rolled wheat) can improve ruminal fermentation, performance as well as adaptation from gestation to lactation in prepartum Holstein cows.