Compartmental flux and in situ methods underestimate total feed nitrogen as judged by the omasal sampling method due to ignoring soluble feed nitrogen flow
Huhtanen, Pekka; Bayat, Alireza; Krizsan, Sophie J.; Vanhatalo, Aila (2013)
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Huhtanen, Pekka
Bayat, Alireza
Krizsan, Sophie J.
Vanhatalo, Aila
Julkaisusarja
British Journal of Nutrition
Volyymi
111
Numero
3
Sivut
535-546
Cambridge University Press
2013
Tiivistelmä
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 5 £ 5 Latin square study with 21 d periods.
Experimental silages of grass or red clover harvested at two stages of maturity in addition to a supplement of 9·0 kg 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 (38 mm 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
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 5 £ 5 Latin square study with 21 d periods.
Experimental silages of grass or red clover harvested at two stages of maturity in addition to a supplement of 9·0 kg 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 (38 mm 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
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