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):
This trust agreement follows previous agreements with ADM that established that calcium oxide (CaO) treatment of corn stover at ensiling improved fiber digestibility. Other studies 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, two diets with TCS substituted at 2 levels for corn grain, and 1 diet with TCS substituted for a portion of the corn silage in the diet. 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. This will be conducted via a specific cooperative agreement with the University of Wisconsin.
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. The 71-cow lactation study with 4 dietary treatments was completed in Winter/Spring 2012. Eight ruminally cannulated cows on the study were used in a 4 x 4 Latin square design, and 63 uncannulated cows were fed a common diet for a two-week covariate period before being offered the treatment diets for a six-week period. Intake, milk production, and animal behavior were recorded. Feed, feed refusal, milk, fecal, and ruminal samples were obtained for analysis. Feed refusal samples were dried, and dry matter content was determined. Individual ingredients of the diets were dried. These ingredients are being subjected to particle-size measurement. Computer entry of behavior data has also been started.