Strategies to Optimize Dietary Energy in Fresh Cow Rations

The transition period from pregnancy to lactation is one of great adaptation for dairy cattle, which too often can lead to metabolic disease and consequently subpar performance throughout lactation. After parturition, cattle enter negative energy balance, as DMI is not able to meet nutrient demands for several weeks, and body reserves are mobilized to compensate for these differences. In fresh cattle diets, the use of Rumensin, an ionophore that increases ruminal production of propionate through a shift in rumen bacteria population, has been shown to increase energy balance, decrease body reserve mobilization, and increase milk yield. Another strategy to increase energy density of the diet is use of higher digestibility corn silage hybrids, such as brown mid-rib (BMR) corn silage. BMR corn silage, which has less overall cross linking within the plant structure, typically provides more digestible aNDFom to the cow than conventional corn silage. Feeding BMR through the periparturient period has been shown to increase DMI and milk production in the early lactation period when compared to conventional corn silage. To investigate any possible synergism of Rumensin and higher digestibility corn silage, 85 multiparous Holstein cattle were moved to a tie-stall 28 days prior to expected parturition to be enrolled in our study. Cattle were fed a common close-up diet for the first seven days consisting of corn silage, chopped straw, and a grain mix, and assigned to treatment diets at 21 days before calving. Cattle fed BMR corn silage performed better overall than those fed conventional corn silage through the transition period. Higher intakes prepartum, as well as higher yield and more favorable circulating blood metabolites in the postpartum period, suggest these cows were in a more positive energy balance than cows fed CON corn silage, likely due to the increased digestible fiber. Cattle fed Rumensin, despite having slightly lower intakes prepartum, had lower circulating BHBA prepartum, as well as lower BHBA and NEFA in the postpartum period. This again suggests that animals were in a better metabolic status. Although we saw minimal statistical interactions between corn silage type and Rumensin, both use different strategies to increase the overall energy availability of the cow. The interaction seen in milk yield data suggests a potential synergism between these two strategies. In this vital transition period these strategies, alone or together, can be key to increase overall cow health and productivity through their impacts on energy availability and overall energy balance.