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 relates to the following objectives of the parent project: Objective 1: Improve accuracy, reproducibility, and ease of measuring/estimating feed digestibility. Sub-objective 1.A: Develop analytical methods that accurately identify and measure critical feed characteristics and digestion products that will enhance our understanding of complex diets needed to develop feeding strategies for improving animal performance. Research Goal 1.A.3: Improve the utility, accuracy, and applicability of in vitro fermentation systems to evaluate in vitro fiber digestibility. Milk samples from the 71-cow lactation study with four dietary treatments (completed in Winter/Spring 2012) are undergoing compositional analysis by the cooperator. Dried feed refusal samples were ground, and processing of fecal samples has begun. Computer entry of behavior data has also been started.