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Effects of induced subacute ruminal acidosis on milk fat content and milk fatty acid profile

Authors

  • F. Enjalbert,

    1. INRA, Université de Toulouse, Tissus Animaux, Nutrition, Digestion, Ecosystème et Métabolisme, Chemin de Borde-Rouge, Auzeville, Castanet-Tolosan Cedex, France; INPT-ENSAT, Castanet-Tolosan Cedex, France; ENVT, Toulouse Cedex, France
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  • Y. Videau,

    1. INRA, Université de Toulouse, Tissus Animaux, Nutrition, Digestion, Ecosystème et Métabolisme, Chemin de Borde-Rouge, Auzeville, Castanet-Tolosan Cedex, France; INPT-ENSAT, Castanet-Tolosan Cedex, France; ENVT, Toulouse Cedex, France
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  • M. C. Nicot,

    1. INRA, Université de Toulouse, Tissus Animaux, Nutrition, Digestion, Ecosystème et Métabolisme, Chemin de Borde-Rouge, Auzeville, Castanet-Tolosan Cedex, France; INPT-ENSAT, Castanet-Tolosan Cedex, France; ENVT, Toulouse Cedex, France
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  • A. Troegeler-Meynadier

    1. INRA, Université de Toulouse, Tissus Animaux, Nutrition, Digestion, Ecosystème et Métabolisme, Chemin de Borde-Rouge, Auzeville, Castanet-Tolosan Cedex, France; INPT-ENSAT, Castanet-Tolosan Cedex, France; ENVT, Toulouse Cedex, France
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F. Enjalbert, École Nationale Vétérinaire, UMR Tandem 1289, 23 chemin des Capelles, BP 87614, 31076 Toulouse, Cedex, France.
Tel: +33 561193910; Fax: +33 561193910;
E-mail: f.enjalbert@envt.fr

Summary

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.

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