ACHIEVING BETTER NITROGEN EFFICIENCY IN LACTATING DAIRY CATTLE: UPDATING FIELD USABLE TOOLS TO IMPROVE NITROGEN EFFICIENCY

摘要

On dairy farms, improving the efficiency of use of feed nitrogen (N) has become a central component of the ration formulation process for two reasons: the desire to be more environmentally friendly and in some cases the ability to reduce feed costs ormake best use of the farm-specific feeds. New data and re-evaluation of feed fractionation techniques are suggesting that how we currently characterize feed protein fractions and their associated degradation and passage rates might cause us to overfeedprotein (Lanzas et al. 2007). Previous papers have discussed some of the relevant concepts and offsets (Chase and Stone, 2004; Van Amburgh et al., 2004; Recktenwald and Van Amburgh, 2006) and reviewed the data concerning the efficiency of dairy cattle toconvert feed N into milk N (Chase, 2003). The objective of this paper is to examine current accounting for various fractions of N in feed, the behavior of these fractions in the rumen, and describe changes in the model library and framework that improvethe sensitivity of predictions to changes in feed N fractions using the Cornell Net Carbohydrate and Protein System (CNCPS)/Cornell-Penn-Miner (CPM) Dairy approach.