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Abstract

The objective of the present study was to estimate ruminal feed N outflow in lactating cows using the omasal sampling, compartmental flux or in situ method. A total of five ruminally fistulated Finnish Ayrshire dairy cows were used in a 5x5 Latin square study with 21d periods. Experimental silages of grass or red clover harvested at two stages of maturity in addition to a supplement of 90kg concentrate/d were fed to the cows. In vivo omasal N flow was determined using the omasal sampling technique. Ruminal in situ N flow was calculated from N intake and degradability (38m nylon bags). The samples of ruminal contents and faeces were divided into seven particle-size fractions by wet sieving; the concentrations of indigestible neutral-detergent fibre and N were used to calculate N flow in the compartmental flux method. In vivo omasal N flow was greater for the red clover silage diets than for the grass silage diets. The N flow calculated using the compartmental flux technique and that calculated using the in situ technique were highly correlated, but both were less than and poorly correlated with the in vivo N flow. In both in situ and compartmental flux techniques, forage maturity increased the particle-associated N flow, with the increase being significantly greater for the red clover diets than for the grass silage diets. In conclusion, the compartmental flux and in situ methods described the N flow associated with the particle fractions rather than the total ruminal outflow of feed N.

Keywords

Feed nitrogen flow; Forages; Compartmental flux method; In situ method; Omasal sampling

Published in

British Journal of Nutrition
2014, volume: 111, number: 3, pages: 535-546
Publisher: CAMBRIDGE UNIV PRESS

SLU Authors

  • Huhtanen, Pekka

    • Department of Agricultural Research for Northern Sweden, Swedish University of Agricultural Sciences

  • Krizsan, Sophie Julie

    • Department of Agricultural Research for Northern Sweden, Swedish University of Agricultural Sciences

UKÄ Subject classification

Animal and Dairy Science

Publication identifier

  • DOI: https://doi.org/10.1017/S0007114513002651

Permanent link to this page (URI)

https://res.slu.se/id/publ/64994