1a. Objectives (from AD-416):
To determine the production, ruminal, and total tract digestion responses of lactating dairy cows to substitution of ensiled calcium oxide-treated corn stover for corn grain or corn silage in their diets.
1b. Approach (from AD-416):
Following on previous research with cooperator that established that calcium oxide (CaO) treatment of corn stover at ensiling improved fiber digestibility, and other studies that showed improved performance in beef cattle fed the CaO-treated corn stover (TCS), this experiment will evaluate the response of lactating dairy cattle to TCS. Corn stover will be ensiled with CaO at the U.S. Dairy Forage Research Center dairy facility in Prairie du Sac, WI. Four experimental diets will be used in an animal study with lactating dairy cows: a control diet with no TCS and three diets with TCS substituted at 3 levels for corn grain. Noncannulated cows (64) used for the lactation and total tract digestion study will be fed a covariate diet for 2 weeks, and then each of the treatment diets will be fed to 1/4 of the cows for 6 weeks. Cows will be sampled/observed for intake milk production, milk composition, behavior, and total tract fiber digestibility during the second week of the covariate period and in weeks 3 and 6 when experimental diets are fed. Cannulated cows (8) will be used in a 4x4 Latin square design in which each of the experimental diets will be fed to 2 cows in each period. In the third week of each 3-week period, feed intake, milk composition, ruminal pH and ruminal fermentation profiles will be measured. Feeds will be analyzed for composition, and forages and TCS for in vitro fiber digestibility. The experimental treatments will be statistically evaluated for their effects on total tract fiber digestibility, milk production and composition, feed intake, feed efficiency, effects on ruminal pH and fermentation measures, and behavior. Samples from this study will be evaluated for fiber digestibility in vitro for comparison/correlation with in vivo fiber digestibility values.
3. Progress Report:
This project is related to Objective 1 of the parent project: Maximize nitrogen (N) use efficiency and animal performance by determining the optimal levels and qualities of dietary protein appropriate for differing base forages in dairy cattle diets, and determining the influence of polyphenol (o-quinones, tannins) or other feed additives on feed N use efficiency. A non-ARS scientist has completed analysis of milk samples from a 71-cow lactation study with four dietary treatments. Processing of all samples and computer entry of data has been completed. The cooperator has completed calculations of diet digestibility and economic analysis of the impact of the treated corn stover on profitability. Statistical analysis of the data has been substantially finished; however, final analyses are in progress.