Effet de l'apport de D,L méthionine, protégée de sa dégradation dans le rumen, aux vaches laitières pendant le tout début de la lactation

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Abstract
The effect of feeding supplementary protected D,L methionine to dairy cows (105 in total) was studied in 3 trials carried out during the first 6 weeks of lactation. In each trial, cows were divided into 2 groups, one of which was supplemented with methionine supplied in decreasing quantities between each of the 3 successive periods of 2 weeks: 20 g, 12 g and 6 g in trials 1 and 2 respectively and, on an average, 18 g, 10 g and 5 g in trial 3 where the quantities offered were individually adjusted to the expected milk production. The basal diet comprised grass silage fed ad libitum and hay fed in limited amounts in trials 1 and 2 and maize silage in limited amounts in trial 3. In the 3 trials, concentrate was offered in limited quantities adjusted for each cow to its expected milk production. The supply of protected D,L methionine on average did not modify milk production, milk composition, feed intake (trials 1 and 2) or liveweight variations during the 6 experimental weeks. Nevertheless, it increased milk production during weeks 1 and 2, highly significantly (2.6 kg/d) or significantly (1.2 kg/d), respectively.