Attempted Control of Paratuberculosis in Dairy Calves by Only Changing The Quality of Milk Fed to Calves

Abstract

Background: The most important route of Mycobacterium avium subsp. paratuberculosis (MAP) transmission is fecal-oral and milk is an important vehicle for MAP transmission to dairy calves. The aim of the present study was to assess the efficacy of treatments for milk being fed to calves as a means of preventing MAP infection transmission. A one-year longitudinal study was carried out on a Chilean dairy farm. New-born calves were assigned to one of four experimental groups. Five calves received naturally MAP-contaminated milk. For comparison, 5 calves received the same milk after treatment with copper ions, 4 calves were fed commercial calf milk replacer and 3 were fed UHT pasteurized milk designed for human consumption purchased from retail stores. MAP concentrations were estimated for copper-treated and untreated milk. Infection progression was monitored monthly. After one year, calves were euthanized, and tissue samples were cultured and visually examined.Results: MAP was undetectable in calf milk replacer and UHT milk. Copper ions treatment significantly reduced the number of viable MAP in naturally contaminated milk. Fecal shedding of MAP was observed in all study groups, but the group of calves fed untreated, naturally contaminated milk began to shed MAP earlier than the rest.Conclusions: Strict dependence on a single intervention to block infection transmission, no matter how important, may fail to control this insidious infection on dairy farms. To be successful, paratuberculosis control programs must use multiple methods to interrupt infection transmission between the source, MAP-infected adult cows, and the most susceptible animals on the farm, young calves.