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 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 nitrogen (N) use efficiency. This was a 71-cow lactation study with four dietary treatments performed by a non-ARS scientist. Eight ruminally cannulated cows were used in a 4 x 4 Latin square design; 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. Computer data have been entered and samples have been analyzed. Complete analyses of data are in progress, including determination of total tract diet digestibility. At least seven farmers have contacted the ARS scientist in Madison, Wisconsin, regarding the outcome of the study with regard to a potential on-farm application of the calcium oxide treatment of corn stover.