Mastitis is a mammary gland inflammatory disease often due to bacterial infections. Like many other infections, it used to be considered as a host-pathogen interaction driven by host and bacterial determinants. Until now, the involvement of the bovine mammary gland microbiota in the host-pathogen interaction has been poorly investigated, and mainly during the infectious episode. In this study, the bovine teat microbiome was investigated in 31 quarters corresponding to 27 animals, which were all free of inflammation at sampling time but which had different histories regarding mastitis: from no episode of mastitis on all the previous lactations (Healthy quarter, Hq) to one or several clinical mastitis events (Mastitic quarter, Mq). Several quarters whose status was unclear (possible history of subclinical mastitis) were classified as NDq. Total bacterial DNA was extracted from foremilk samples and swab samples of the teat canal. Taxonomic profiles were determined by pyrosequencing on 16s amplicons of the V3-4 region. Hq quarters showed a higher diversity compared to Mq ones (Shannon index: ~8 and 6, respectively). Clustering of the quarters based on their bacterial composition made it possible to separate Mq and Hq quarters into two separate clusters (C1 and C2, respectively). Discriminant analysis of taxonomic profiles between these clusters revealed several differences and allowed the identification of taxonomic markers in relation to mastitis history. C2 quarters were associated with a higher proportion of the Clostridia class (including genera such as Ruminococcus, Oscillospira, Roseburia, Dorea, etc.), the Bacteroidetes phylum (Prevotella, Bacteroides, Paludibacter, etc.), and the Bifidobacteriales order (Bifidobacterium), whereas C1 quarters showed a higher proportion of the Bacilli class (Staphylococcus) and Chlamydiia class. These results indicate that microbiota is altered in udders which have already developed mastitis, even far from the infectious episode. Microbiome alteration may have resulted from the infection itself and or the associated antibiotic treatment. Alternatively, differences in microbiome composition in udders with a history of mastitis may have occurred prior to the infection and even contributed to infection development. Further investigations on the dynamics of mammary gland microbiota will help to elucidate the contribution of this endogenous microbiota to the mammary gland health.

-We studied the feeding behaviour of cattle offered unconstrained choices between two hays of either different or similar nutritive values, and linked these choices to their behaviour when the same forages were offered alone. Over successive 10-day periods, six 15-month-old Aubrac heifers received three hays (a leafy one, G, and two late cut ones, C1 and C2, of very similar nutritive value), ad libitum, alternately alone and associated two by two. As expected, the heifers ate more G than C1 or C2 when the hay was offered alone, and preferred G in choice trials. They displayed a similar behaviour towards C1 and C2 when they were given alone, and also when they were independently associated with G (C1 and C2 making up 18% and 17% of the total intake and 21% and 17% of total feeding time, respectively) or when they were offered together (each accounting for nearly 50% of the total intake or feeding time). The choices could be related to the daily intakes of the forages given alone, which could thus be a good predictor of relative daily intakes under choice conditions. Heifers always showed partial choices, which could be seen as the research of the maintenance of optimal ruminal conditions, the result of sampling behaviour and/or the pleasure associated with the diversity of the diet. Their tendency to diversify the diet was also supported by the reaction to the recent diet by temporarily increasing their preference for the hay that had not been offered during the previous nochoice sub-period. Finally, all the choice situations raised the daily dry matter intake, which could be seen as the result of their motivation to eat due to the diversity of the offer. de regain G et deux foins tardifs C1 et C2 de valeurs alimentaires similaires) à volonté, alternativement distribués seuls ou associés deux par deux. Les génisses ont ingéré G en plus grande quantité que C1 ou C2 lorsque les foins étaient distribués seuls et l'ont préféré en situation de choix. Elles ont eu des comportements similaires vis-à-vis de C1 et de C2 distribués seuls, mais également lorsqu'ils étaient offerts avec G (C1 et C2 représentant respectivement 18 % et 17 % des quantités ingérées totales, et 21 % et 17 % du temps d'ingestion) ou lorsqu'ils étaient distribués ensemble (chaque foin représentant environ 50 % des quantités ingérées et du temps d'ingestion). Les choix étaient en accord avec l'ingestibilité des fourrages distribués seuls, qui pourrait donc être un bon critère de prévision des quantités ingérées relatives en situation de choix. Les génisses ont toujours montré des choix mixtes, ce qui peut être interprété comme la recherche d'un maintien de conditions ruminales optimales, le résultat d'un comportement d'échantillonnage et/ou du plaisir associé à un régime diversifié. Leur tendance à diversifier le régime s'est également exprimée lors du passage d'une situation de non choix à une situation de choix, par l'augmentation temporaire de leur préférence pour le foin qui n'avait pas été distribué précédemment. Enfin, la situation de...

-During winter, beef cows in large herds are now more often accommodated with group feeding systems. However, the recommended allowances for feeding beef cows are primarily based on results obtained with tethered animals. The feed intake and feeding behaviour of 47 Charolais cows fed hay ad libitum were thus compared over two successive winters in a stanchion tie-stall system (TS) and in a loose housing system (LH) using 24

-The criteria used by farmers to assign animals to the different groups do not only concern nutritional aspects, implying that each group is not homogeneous with regards to nutrient requirements. The food intake and feeding behaviour of 12 loose-housed Charolais cows (6 dry and 6 lactating), given hay ad libitum were compared in homogeneous (Hom) and heterogeneous (Het) groups according to their physiological states: Hom groups were comprised of cows in similar physiological states (dry or lactating) and Het groups were comprised of cows in different physiological states (dry + lactating).