|Waghorn, Garry - DEXEL LIMITED, NEW ZEALAN|
|Mccaslin, Mark - FORAGE GENETICS, ST. PAUL|
Submitted to: Journal of Dairy Science
Publication Type: Abstract Only
Publication Acceptance Date: July 10, 2006
Publication Date: July 10, 2006
Citation: Hatfield, R.D., Grabber, J.H., Sullivan, M.L., Waghorn, G., Mccaslin, M. 2006. Transforming Forage Plants to Increase Nitrogen Utilization in Dairy Systems: What Are the Possibilities? Journal of Dairy Science. 89(supplement 1):633. Technical Abstract: Forages can supply adequate protein to meet the nutritional needs of high producing dairy cows, at least as the crop stands in the field. However proteins are one of the most labile nutritional components in most forages, often being excessively degraded during ensiling and ruminal digestion, leading to depressed amino acid absorption and excessive urea excretion by cattle. Even when forages are grazed, protein-use efficiencies are often low due to rapid plant cytoplasmic protein degradation in the rumen. To maintain high production dairy diets are frequently supplemented with a protein source to compensate for poor forage protein use. Traditional breeding and molecular approaches can be used to modify forages for improved protein-use by cattle. For example, redesigning alfalfa to produce polyphenol oxidase and o-diphenols or condensed tannins would lead to decreased protein degradation during ensiling and ruminal digestion with a likely increase in amino acid absorption by cattle. Production and feeding of such a forage would reduce urea excretion and possibly slow nitrogen release from feces and crop residues, thereby reducing nitrogen losses form farms. Altering specific gene expression in the lignin pathway may allow decreased lignification and increased fiber digestion for improved nitrogen utilization. Genetic selection or molecular alteration of forages to produce greater quantities of rapidly fermented carbohydrates should enhance conversion of non-protein nitrogen to ruminal protein for utilization by cattle. Increasing total biomass production that has good quality remains a challenge for forage production. Exploiting the genetic potential for total biomass production in forages is just now being explored. It is not an impossible task to redesign forages to function more efficiently as effective nitrogen sources for dairy cows, decreasing the need for additional protein supplements, and ultimately decreasing nitrogen losses to the environment.