Effect of Transition to the Dry Period on Fecal Shedding of Coliform Bacteria in Dairy Cows
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Date
2016-12
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The Ohio State University
Abstract
On well-managed dairy farms, environmental mastitis leading to clinical mastitis (CM) in dairy cows is common, and the most likely cause identified is certain gram-negative bacteria. Clinical mastitis is a very costly disease for farmers, limiting milk production and saleable milk, as well as negatively affecting milk quality. Previous studies have shown that the dry period is a critical time in the development of new intramammary infections that persist into the next lactation. In some beef feedlot studies, large increases in grain have resulted in increased fecal shedding of E. coli bacteria. Cows are fed primarily a high grain diet and a forage-based diet in lactation and the dry period, respectively. Lactating cows are fed high levels of grain to support high milk yields. The high level of grain in late lactation may be associated with higher fecal shedding of bacteria compared to the dry period when lower levels of grain are fed. The objective of this study was to quantify the effect of a rapid change in grain levels in the diet by measuring fecal shedding in dairy cows before and after dry-off. Fecal samples, from cows at two dairy farms either one week before drying off (n = 25) or two weeks into the dry period (n = 30), were taken rectally and immediately plated on MacConkey agar plates, selecting for coliform bacteria. The numbers of coliform bacteria in the feces of cows were measured to quantify the shift in bacterial shedding counts as affected by the transition between lactation and dry-off. Results showed no change in coliform levels between late-lactation and the dry period (P = 0.78). Because high variability of coliform fecal shedding was seen between cows on each farm, detection of changes associated with grain feeding were likely masked; however, additional studies following cows through the transition from lactation to dry-off are needed to confirm.
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Keywords
cows, cow, dairy, coliform, fecal shedding