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TDK conference 2015

The effects of subclinical Mycobacterium avium ssp. paratuberculosis infection on the health and production parameters of dairy cows
Bognár Barbara - year 6
SzIU, Faculty of Veterinary Science, Department of Animal Hygiene, Herd-health and Veterinary Ethology
Supervisors: Dr. Jurkovich Viktor, Dr. Mézes Miklós


Paratuberculosis (also called Johne’s disease) is a chronic disease caused by Mycobacterium avium ssp paratuberculosis. The bacterium causes a chronic disease which manifests at 3 or 4 years of age, usually after the 2nd lactation period and causes an incurable disease. The pathogen occurs worldwide in dairy herds being one of the most economically important infectious disease of ruminants. During the past decades many articles have been published about the damage of the disease, but the effects of the subclinical stadium are still unclear. The infected animals shed the pathogen intermittently during the different states of the disease which makes it so hard to diagnose. The diagnosis of the disease in the subclinical state is the hardest, because there are no reliable laboratory tests.

Our objective was to find out how the subclinical state of the disease influences the metabolism of the animals. Our other objective was to evaluate the production and health data of the examined and the pre-examined lactation periods.

The effect of subclinical paratuberculosis infection on the health and production parameters of cows was studied in a Hungarian dairy herd. 15 infected (no clinical signs, but faeces PCR positive) and 15 healthy (faeces PCR negative) cows were involved in the study.

During the study the keeping and feeding conditions of the individuals of the control and the infected group were the same.

Blood and urine samples were taken starting from the 2nd week prepartum to 120 days postpartum and production data were collected.

The following parameters were determined from blood plasma: total protein, albumin, total cholesterol, triglyceride, BHB, NEFA and urea, and AST and GGT. From the urine pH and NABE has been measured. Along with the sampling we performed body condition scoring.

We also collected data about the production (milk yield, milk fat, milk protein) and health and reproduction (number of mastitis treatments, number of treatments due to reproductive tract problems, length of service period, number of AI’s).

No statistically significant difference was observed regarding the blood samples of the two groups.

The body condition of the infected animals was significantly worse than that of the healthy ones, the milk yield tended to be lower in the infected group. Other health and reproductive parameters (number of mastitis treatments, number of treatments due to reproductive tract problems, length of service period, and number of AI’s) were significantly worse compared to the control group. First service conception rate was considerably lower in the infected group.

The subclinically infected cows are more susceptible to other diseases therefore we have to calculate with increased veterinary costs. Usually the disease occurs latently which explains why the farmers do not pay much attention to prevention and eradication.

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