The Influence of Protein Level on the Nitrogen Absorption in the Gastro-Intestinal Tract of Dairy Cows Fed Grass Silage Fertilized With Two Levels of Nitrogen

Abstract

Increased recycling of nitrogen to the forestomachs on low nitrogen rations was found. On high CP rations the AAN at duodenum was greater than or equal to the N intake. Apparently absorbed TN in the small intestine was increased on the SBM supplemented ration. No significant difference was found for absorbed AAN fractions.Key words: Nitrogen, cattle, metabolism, gastro-intestinal tract Results by Lambert et al. (1975) showed that increased nitrogen fertilization to grass, 0-400 kg N/ha, raised the amount of crude protein from 8.6 to 20.6% in DM and the amount of NPN from 0.8 to 5.2Vo, respectively. As a proportion of total CP the amount of NPN varies from 9 to 25Vo in fresh grasses (Lambert et al. 1975) For personal use only.

A Rapid Procedure for Purine Measurement and Its Use for Estimating Net Ruminal Protein Synthesis

“…Combining this purification procedure with the hydrolysis procedure of Marshak and Vogel (1951) In that trial, acid-precipitated casein was included as one source of N. As some of this insolubilized casein escaped ruminal digestion in a subsequent study (Zinn and Owens 1983) Storm et al (1983) by Savage (19'77), 697o by Santos et ai. (1982), 69-1l%o by Merchen and Satter (1983), 6l-7O7o by Hvelplund (1984),70-137o by Moller et al (1984) (Ling and Buttery 1978;Siddons et al 1982 (Smith 1969(Smith , 1975Czerkawski 1976), though Ling and Buttery (1978) (Siddons et al 1982) but should not alter purine content (Ha and Kennelly 1984). In addition, backflow of digesta into the duodenum following intestinal hydrolysis of polynucleotides but before absorption of nucleic acids from the small intestine should not alter purine recovery if any backflow of digesta is accompanied by the digesta marker.…”