Udder diseases in dairy cows — field observations on incidence, somatic and environmental factors, and control

The incidence of udder diseases and the predisposing factors were examined in 32 herds, in a total of 500 cows. During a 3-year-period 0.32 cases of clinical mastitis occurred per cow per annum. Subclinical mastitis was detected in 61.2 % of the cows during one year. The average incidence based on a single sampling was 36.5 %. In order to obtain reliable information on the udder health of a herd the occurrence of both clinical and subclinical mastitis must be followed. Clinical cases, both those treated by a veterinarian on a farm visit and those treated by the owner according to phone prescription must be filed statistically. In this study the incidence of mastitis as reported by owner was only half of that actually detected. The incidence of teat injuries requiring veterinary treatment was 0.03 cases per cow per annum. The diagnosis »presence of bacteria» obtained from a milk sample examination using Nordic methods means according to this study in most cases the probable occurrence of infection and mastitis. Scoring of observations made from udder health, and indexes based on these scores prove to be good tools when studying relationships between udder diseases and predisposing factors. Of the somatic factors the age of the cow, stage of lactation, the distance of the rear teats from the stall floor and the position of the teats influence the incidence of mastitis. Therefore, these factors must be taken into consideration in preventive work, especially in the culling of cows. Neither teat shape nor milkability had any connection with the incidence of udder diseases. With regard to the factors in the production environment the incidence of clinical mastitis was influenced especially by the function of the milking machine. Diurnal changes in temperature, when exceeding5 degrees centigrade, increased the occurrence of mastitis. The use of a thermohygrograph is proposed in preventive work. Because of the small number of the herds only in few cases reliable proof could be obtained as to whether the constructional details of the cowshed or stall or the milking hygiene had any effect on udder health. The observations made, however, were not in disagreement with those findings published in other Nordic countries. The significance of the cattle tender as an environmental factor is great. When a mastitis control programme is worked out, therefore, the mastitis situation in a herd, and the predisposing factors detected on the farm must be reliably demonstrated to the owner and the measures required for improvement must be clearly proposed