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Individual animal variability in ruminal bacterial communities and ruminal acidosis in primiparous Holstein cows during the periparturient period

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The purpose of this study was to investigate variability among individual cows for their susceptibility to ruminal acidosis (RA) pre- and postpartum, and determine whether this variability was related to differences in their ruminal bacterial community composition (BCC). Variability in susceptibility to RA among individual cows was characterized based on ruminal fermentation variables. Effects of prepartum dietary treatment on susceptibility of cows to RA were also examined. Fourteen Holstein heifers paired by expected calving date and BCS were allotted to 1 of 2 prepartum dietary treatments: low concentrate (2 diets ranging from forage:concentrate (F:C) = 80:20 to 54:46); or high-concentrate (4 diets ranging from F:C = 68:32 to 46:54). All cows received the same lactation diet postpartum. Microbial DNA extracted from 58 rumen digesta samples collected prepartum (d -50, -31, -14) and postpartum (d +14, +52) and amplified by PCR were subjected to automated ribosomal intergenic spacer analysis (ARISA). Changes in ruminal variables [pH, volatile fatty acids (VFA), and acidosis indicators measured at d -54, -35, -14, -3, +3, +17, +37, +58] were analyzed using principal component analysis (PCA). Based on the shift (defined as the distance of the mean loadings) between the prepartum and postpartum period for each cow, the 14 cows were classified into 3 groups: less acidotic (LA; n=5), more acidotic (MA; n=5), and intermediate (IN; n=4). Cows in the MA group had greater severity of RA (measured as duration of total RA, mild RA, moderate RA and acute RA; area under pH curve for total RA, mild RA, and moderate RA) postpartum than prepartum, and this difference between periods was greater than for the LA cows. The variation in susceptibility to RA was independent of intake, total VFA and individual VFA. However, RA index (total area of pH < 5.8 normalized to intake) showed interaction between susceptibility and period. Production variables (milk yield, fat %, fat yield, FCM, efficiency of milk production) were not influenced by susceptibility to RA. Ruminal BCC was not influenced by dietary treatment or period. However, a shift in BCC occurred across periods for some cows. Based on the magnitude of the shift in BCC (distance between mean ordination values across the periods for each cow), cows were grouped into 3 BCC profile categories: stable (5 cows with lesser shift), unstable (5 cows with greater shift) and intermediate (4 cows with average shift). Cows demonstrating a greater shift in BCC were not necessarily those in the MA group and vice versa. The relationship between the shifts in ruminal fermentation variables (PCA rankings) and the shifts in BCC (ARISA rankings) were not related (n = 14; r2 = 0.00; P = 0.98). It was concluded that not all cows are equally susceptible to RA, and shifts in BCC appear to be independent of differences in the severity of RA postpartum.
R. Mohammed , D. M. Stevenson , P. J. Weimer , G. B. Penner , K. A. Beauchemin
USDA Scientist Submission
Journal of dairy science 2012 v.95
American Dairy Science Association
Journal Articles, USDA Authors, Peer-Reviewed
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