Relation of net portal flux of nitrogen compounds with dietary characteristics in ruminants: A meta-analysis approach

Roger Martineau (1) , Daniel Sauvant (2) , Daniel R. Ouellet (1) , Cristiano Côrtes (1) , Jean Vernet (3) , Isabelle Ortigues Marty (3) , Hélène Lapierre (1)

1 Dairy and Swine Research and Development Centre
2 MoSAR - Modélisation Systémique Appliquée aux Ruminants
3 URH - Unité de Recherches sur les Herbivores

Decrease of N intake (NI) with the aim of increasingefficiency of N utilization and decreasing the negativeenvironmental effects of animal production requires assessmentof the forms in which N is absorbed. A metaanalysiswas conducted on 68 publications (90 experimentsand 215 treatments) to study the effect of NI onnet portal appearance (NPA) of nitrogenous nutrients[amino acids (AA), ammonia, and urea] in ruminants.In addition, the effect of several dietary energy andprotein factors on this relationship was investigated.These factors were dry matter intake; proportion ofconcentrate; diet concentrations and intakes of nonfibercarbohydrates and neutral detergent fiber (NDF); dietconcentrations of total digestible nutrients (TDN) andcrude protein; rumen-degradable protein and rumenundegradableprotein, as percent dry matter or percentcrude protein. The effect of species and physiologicalstage was also investigated. Within-experiment analysesrevealed that the NPA of AA-N and ammonia-Nincreased linearly, whereas the NPA of urea-N decreased(or recycling of urea-N increased) linearly withNI. Besides NI, many significant covariates could beintroduced in each NPA model. However, only TDNand neutral detergent fiber intake (NDFi) were commonsignificant covariates of NI in each NPA model. Inthis database, ruminants converted 60% of incrementalNI into NPA of AA-N with no species effect on thatslope. However, at similar NI, TDN, and NDFi, sheepabsorbed more AA-N than did cattle and dairy cows.On the other hand, species tended to affect the slopeof the relationship between NPA of ammonia-N andNI, which varied from 0.19 for the sheep to 0.38 fordairy cows. On average, the equivalent of 11% of incrementalNI was recycled as urea-N to the gut throughthe portal-drained viscera, which excludes salivarycontribution, and no species difference was detected.Overall, at similar TDN and NDFi, sheep and cattleincreased their NPA of AA-N relative to NI incrementby a similar magnitude. The higher absorption of AA-Nobserved in sheep compared with cattle, at similar NI,TDN, and NDFi, might result from lower losses of AAthrough portal-drained viscera metabolism.

Mots clés: urea; portal; amino acid; ammonia

Domaines: Sciences agricoles

Roger Martineau, Daniel Sauvant, Daniel R. Ouellet, Cristiano Côrtes, Jean Vernet, et al.. Relation of net portal flux of nitrogen compounds with dietary characteristics in ruminants: A meta-analysis approach. Journal of Dairy Science, 2011, 94 (6), pp.2986-3001. ⟨10.3168/jds.2010-3438⟩. ⟨hal-01003261⟩