AcID - Indicateurs de diagnostic et suivi de l’acidose ruminale subaiguë dans les troupeaux de vaches et chèvres laitières

The AcID (acidosis and diagnosis indicators) project was funded by CasDar and began in January 2014. The aim of the project was to use milk fatty acids profile to predict ruminal fermentations and subacute ruminal acidosis (SARA). The estimation of milk fatty acids profiles in routine using mid infrared (MIR)spectroscopy coupled with field surveys were supposed to make it possible to calculate SARA frequency in dairy cows herds and dairy goats flocks. This method was also supposed to make it possible to identify sensitive animals and risky feeding practices, and to evaluate the effects of SARA on animal health and milk production. In dairy cows, a curvilinear relationship between even to odd fatty acids ratio in milk and ruminal acetate to propionate (C2/C3) ratio has been brought to light. Milk MIR spectra were used to build an equation to estimate C2/C3 ratio in routine with quite good precision (R² = 0.82). In dairy goats, no relationship between milk fatty acids and ruminal fermentation parameters has been highlighted, and the estimation of fermentation parameters directly from MIR spectra was not precise enough. A case-control survey was led in 60 dairy cows herds which were recruited on the basis of their milk fatty acids profile and fat to protein ratio. 94 field surveys were conducted in dairy goats flocks on the basis of their feeding practices. Results from the surveys are similar between species: very few SARA cases were observed or suspected, the feeding practises identified as risky were already known, and the strategy used to prevent SARA is working quite well. Le projet CasDar AcID (acidose et indicateurs pour le diagnostic) a débuté en janvier 2014. Son objectif était d’utiliser le profil en acides gras (AG) du lait comme prédicteur des paramètres fermentaires du rumen et donc de l’acidose ruminale subaiguë (ARSA) chez la vache laitière et la chèvre laitière. Laquantification de ces profils en routine par spectrométrie moyen infrarouge (MIR) devait permettre, via des enquêtes en élevage, d’estimer la fréquence de l’ARSA dans les troupeaux, d’identifier les animaux les plus sensibles et les pratiques alimentaires à risque, et d’évaluer les effets de l’acidose sur la santédes femelles et leurs performances de production. Chez la vache laitière, le projet a permis de mettre en évidence une relation curvilinéaire entre un ratio d’AG pairs/AG impairs du lait et le rapport acétate sur propionate (C2/C3) du jus de rumen. Une équation spécifique a