Submitted to: Journal of Dairy Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: June 28, 2001
Publication Date: November 1, 2001
Citation: Greenfield, T.L., Baldwin, R.L., Erdman, R.A., Mcleod, K.R. 2001. Ruminal fermentation and intestinal flow of nutrients by lactating cows consuming brown midrib corn silages. Journal of Dairy Science. 84(11):2469-2477.
Interpretive Summary: Recent advances in the development of genetic varieties of corn have facilitated the commercialization of corn varieties that have desirable characteristics for dairy cattle production. One of the potentially beneficial variants is brown midrib corn which has fiber characteristics which could make it a valuable crop for feeding to dairy cattle. This experiment evaluated digestion characteristics of brown midrib (BM3)corn silage to see if it will be beneficial to dairy farmers. Breakdown of a majority of the components of the BM3 corn silage in the rumen of dairy cattle was enhanced. Additionally, amounts of starch consumed and digested in the total tract were greater, but ruminal starch digestion was less, suggesting that more of the starch was available for absorption post-ruminally for the BM3 treatment. Furthermore, although nitrogen (N) intake and digestion were greater for the BM3 treatment N losses to the urine were not increased indicating that BM3 promotes a better N economy for the dairy cow. Thus, true benefits of BM3 may be realized by dairy cows at peak production where increases in nutrient delivery and N economy might be combined with greater feed intake to result in increased milk production without increases in the negative impact of N excretion on the environment.
Ruminal characteristics and total digestion of brown midrib corn silage was evaluated using five multiparious cows in late lactation. Total mixed rations were fed containing 60% corn silage and 40% concentrate. The treatments were brown midrib (BM3) and isogenic (ISO) corn silage that were applied in a reversal design with two 21-d periods. Apparent rumen digestibility of DM and OM were greater with the BM3 treatment. Amounts of starch consumed and digested in the total tract were greater, but ruminal starch digestion was less, suggesting that more of the starch was available for absorption post-ruminally for the BM3 treatment. Ruminal and total tract NDF and ADF digestibilities were higher for BM3 treatment. These data show that digestion was partitioned toward the rumen microbial population for the BM3 treatment. Rumen pH was lower with the BM3 treatment. Nitrogen intake and digestion was higher for the BM3 treatment versus the ISO treatment. However, there was no difference in urinary N excretion. This suggests a better N economy for the cows on the BM3 treatment. The true benefit of BM3 may be realized by cows at peak production, where these increases in digestibilities and N economy might be combined with a higher DMI, frequently observed with feeding BM3 corn silage.