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This Article Full Text Full Text (PDF) Supplemental data All Versions of this Article: jas.2008-1729v1 87/10/3300    most recent Alert me when this article is cited Alert me if a correction is posted Services Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Google Scholar Articles by Martineau, R. Articles by Lapierre, H. PubMed PubMed Citation Articles by Martineau, R. Articles by Lapierre, H.

Technical note: Correction of net portal absorption of nitrogen compounds for differences in methods: First step of a meta-analysis^1,2

R. Martineau^*, I. Ortigues-Marty, J. Vernet and H. Lapierre^*,3

^* Dairy and Swine Research and Development Centre, Agriculture and Agri-Food Canada, Sherbrooke, Quebec, Canada J1M 1Z3; and Institut National de la Recherche Agronomique, UR1213 Unité de Recherches sur les Herbivores, Theix, 63122 St Genès Champanelle, France

³ Corresponding author: Helene.Lapierre{at}agr.gc.ca

The objective of this study was to evaluate the usefulness of correcting net portal absorption (NPA) of urea-N, ammonia, and AA-N for differences in methods before their inclusion into a meta-analysis. It was hypothesized that the difference, or portal-drained viscera (PDV) balance, between N inputs (apparently digested N plus urea-N) and outputs (ammonia plus AA-N) was 0 in the absence of measurement errors and based on the assumption that other sources of N inputs and outputs were relatively small and balanced each other. A database was built from 44 publications that reported data from 129 treatments (sheep, n = 71; beef cattle, n = 32; and dairy cows, n = 26). When necessary, NPA of urea-N (n = 38) and ammonia (n = 35) results were recalculated on a whole-blood basis, whereas NPA of AA-N (n = 87) was recalculated for all the N from AA transferred across the PDV rather than only the N from the -amino group. Before corrections, PDV balance averaged 22.9% of N ingested (SD 29.0) for all treatments; after corrections, PDV balance significantly decreased to 10.2% of N ingested (SD 34.7). No difference in PDV balance was observed among species before or after corrections. Correcting NPA of urea-N, ammonia, and AA-N increased the accuracy without improving precision. Therefore, from a biological perspective, recalculating reported data seems appropriate to reduce bias due to differences in methods because this approach reduces the excess in N inputs relative to N outputs.

Key Words: amino acid • ammonia • meta-analysis • portal flux • ruminant • urea