Characteristics of Nitrogen Fractions and Amino Acids of Feedstuffs Common to the Pacific Northwest

Abstract

Thirty-nine forage samples and 47 grain and by-product feed samples were collected from various sites in Washington. Total crude protein (total N), soluble protein (soluble N), soluble nonprotein N (soluble NPN), soluble true PN, neutral detergent insoluble N (NDIN), and acid detergent insoluble N (ADIN) were determined. The soluble N in forages contributed 30 to 70% of total N, in which 60 to 80% was soluble NPN. Grains and by-product feeds had a lower percentage of soluble Nand NPN. Nitrogen degradability of feeds was estimated by Streptomyces grise us fermentation and in situ disappearance in the rumen. Effective N degradability of feeds was calculated. The rate and extent of N degradability offeeds, estimated by in situ technique, were generally greater than by S. griseus. In situ N degradability of most feeds could be accurately predicted by its DM degradability or by S. griseus N degradability. The proportion of microbial N in the incubated feeds was calculated from concentrations of purines or diaminopimelic acid. Eighty to 90% of total N for most feeds was degraded in the rumen after 24h of incubation.