Genetic variation of maize silage ingestibility in dairy cattle

During a three-year experiment, twelve registered or experimental maize hybrids were investigated for their ingestibility in dairy cows. Their digestibility values in sheep were also available from simultaneous experiments. Significant intake differences were observed between maize hybrids, ranging from 14.4 to 17.9 kgcow -1 day -1 . The highest intake was observed for the bm3 hybrid. Among normal hybrids, DK265 had a higher ingestibility than other hybrids. However, two recently registered hybrids and an experimental hybrid had only little lower values of intake than DK265. In vivo NDF digestibility explained about 50% of the intake variation (bm3 hybrid excluded), but in vitro cell wall digestibility (DINAGZ) explained only 25% of the intake in similar conditions. Ingestibility variation were probably related to both rate of cell wall degradation and friability traits, that are not relevantly measured through usual digestibility or lignin content estimates. ingestibility / maize / genetic variation / cell wall digestibility / lignin / breeding Rsum -Variabilit gntique de l'ingestibilit du mas ensilage mesure sur des vaches laitires. L'ingestibilit de douze hybrides de mas, inscrits ou exprimentaux, a t tudie sur vaches laitires au cours d'une exprimentation rpartie sur trois annes conscutives. Leurs valeurs de digestibilit sur moutons taient galement disponibles partir d'exprimentations simultanes aux mesures sur vaches laitires. Des diffrences significatives d'ingestibilit ont t observes entre hybrides, comprises entre 14.4 et 17.9 kgvache -1 jour -1 , l'hybride bm3 ayant la valeur la plus leve. Au sein des hybrides normaux, DK265 avait une ingestibilit suprieure aux autres hybrides, mais un hybride rcemment inscrit et un hybride exprimental avaient des valeurs d'ingestibilit proches. La digestibilit in vivo du NDF expliquait environ 50 % de la variabilit observe pour l'ingestibilit (hybride bm3 exclu), mais la digestibilit in vitro des parois estime par le critre DINAGZ n'en expliquait dans les mmes conditions que 25 %. La variabilit de l'ingestibilit est trs probablement relier autant des caractristiques de vitesse de dgradation et de friabilit des parois, non values travers les critres classiques, qu' la digestibilit des parois proprement dite. ingestibilit / mas / variabilit gntique / digestibilit des parois / lignine / amlioration gntique