title: Effects of induced subacute ruminal acidosis on milk fat content and milk fatty acid profile.
abstract: Two lactating dairy cows fitted with a rumen cannula received successively diets containing 0%, 20%, 34% and again 0% of wheat on a dry matter basis. After 5, 10 and 11 days, ruminal pH was measured between 8:00 and 16:00 hours, and milk was analysed for fat content and fatty acid profile. Diets with 20% and 34% wheat induced a marginal and a severe subacute ruminal acidosis respectively. After 11 days, diets with wheat strongly reduced the milk yield and milk fat content, increased the proportions of C8:0 to C13:0 even- or odd-chain fatty acids, C18:2 n-6 and C18:3 n-3 fatty acids but decreased the proportions of C18:0 and cis-9 C18:1 fatty acids. Wheat also increased the proportions of trans-5 to trans-10 C18:1, the latter exhibiting a 10-fold increase with 34% of wheat compared with value during the initial 0% wheat period. There was also an increase of trans-10, cis-12 C18:2 fatty acid and a decrease of trans-11 to trans-16 C18:1 fatty acids. The evolution during adaptation or after return to a 0% wheat diet was rapid for pH but much slower for the fatty acid profile. The mean ruminal pH was closely related to milk fat content, the proportion of odd-chain fatty acids (linear relationship) and the ratio of trans-10 C18:1/trans-11 C18:1 (nonlinear relationship). Such changes in fatty acid profile suggested a possible use for non-invasive diagnosis of subacute ruminal acidosis.
authors.affiliation: INRA, Université de Toulouse, Tissus Animaux, Nutrition, Digestion, Ecosystème et Métabolisme, Chemin de Borde-Rouge, Auzeville, Castanet-Tolosan Cedex, France. f.enjalbert@envt.fr
authors.forename: F
authors.initials: F
authors.lastname: Enjalbert
authors.forename: Y
authors.initials: Y
authors.lastname: Videau
authors.forename: M C
authors.initials: MC
authors.lastname: Nicot
authors.forename: A
authors.initials: A
authors.lastname: Troegeler-Meynadier
mesh_terms: D000138:Acidosis / Q000175:diagnosis / Q000378:metabolism / Q000662:veterinary*; D000821:Animal Feed; D000824:Animal Nutritional Physiological Phenomena; D000818:Animals; D002417:Cattle / Q000502:physiology; D002418:Cattle Diseases / Q000175:diagnosis / Q000378:metabolism*; D005227:Fatty Acids / Q000032:analysis*; D005260:Female; D006863:Hydrogen-Ion Concentration; D007774:Lactation; D008892:Milk / Q000737:chemistry* / Q000378:metabolism; D012417:Rumen / Q000378:metabolism*; D014908:Triticum
chemical_list: D005227:Fatty Acids