EFFECTS OF GLYCEROL SUPPLEMENTATION OF THE DIET OF DAIRY-COWS ON MILK-PRODUCTION AND SOME DIGESTIVE AND METABOLIC PARAMETERS

In 3 trials (57 Holstein lactating cows in total), 2 of which were carried out at the beginning of lactation, 190-610 g glycerol were added to the ration daily in substitution for the same quantity of concentrate. Animals were fed according to standards, with diets based on grass silage and hay + fodder beet roots. Glycerol supply had no effect on milk yield and composition and on food intake (measured in 1 trial). It increased the proportion of propionic and butyric acids in the volatile fatty acid mixture of the rumen juice to the detriment of acetic acid. In blood plasma, it increased 3-hydroxybutyrate concentration and decreased glycemia (1 trial). Addition of glycerol to the diet does not appear to be effective in avoiding ketosis in dairy cows when used at the same doses as in our trials.