Evaluation of the effects of synchronising the availability of N and energy on rumen function and production responses of dairy cows – a review

This paper reviews the effects of synchronising the availability of N and energy on rumen function and production responses of lactating dairy cows. The paper makes a key distinction between altering the synchronicity of diets by changing dietary ingredients, or by altering the feeding frequency or the feeding patterns. Manipulating synchrony by changing dietary ingredients presents some problems, since it is not possible to discount the possibility that apparent effects of synchrony are associated with the manipulation of the ingredients (level and type) themselves. These problems can be overcome, at least partially, by altering the feeding patterns. This review shows that the evidence for the benefits of synchronising energy and N supply to the rumen is contradictory, both for efficient microbial protein synthesis and for maximising milk production responses. dairy cow / energy / nitrogen / rumen / synchrony Rsum -Effets de la synchronisation de la disponibilit en azote et en nergie sur la fonction ruminale et les performances de production des vaches laitires -revue. Cet article passe en revue les effets d'une synchronisation entre les disponibilits en azote et en nergie sur la fonction ruminale et les performances de production des vaches laitires. Une distinction importante est faite entre les effets d'une synchronisation obtenue en changeant les ingrdients de la ration, et celle obtenue en modifiant le schma et la frquence d'apport d'aliment. La premire solution conduit des difficults d'interprtation, car il devient impossible de distinguer les effets de la synchronisation de ceux dus la nature et au niveau des ingrdients utiliss. La deuxime solution permet, au moins