Structural change of agriculture has increased production volume which has made respiratory infections a more common problem in enlarged units. What makes respiratory infections more common are larger calf groups, decreased immunity and mixing together animals with different origins. Especially in feedlot calf barns respiratory infections have become a common problem when groups are formed of calves from various dairy farms. This thesis was made in collaboration with Tuottava pohjalainen naudanlihantuotanto -project and A-Tuottajat Oy. A private farmer disclosed the calf health and growth data for this project.

The aim of this thesis was to produce an experiment on the infection and growth effects of calf grouping by their origin. The main intent was to investigate if calves from large scale dairy farms have better performance than calves from smaller farms.

In the experiment calves were grouped by their birth farms scale. The base of the experiment was data of calf medications received from Naseva cattle healthcare tracking system. The test was formed from five separate replicates which provided information from 750 calves. At the start and in end the calves were weighed which provided their daily growth.

The results did not provide clear information if there were more immune calves in the group which came from larger farms. However, heifer calves were much healthier than the actual test group which included only bull calves. There seemed to be a partial correlation between daily gain and respiratory infections. Test results proved that the best way to group cattle in a calf byre could be by their health status. Sick animals should be isolated in separate groups so the infections would not spread further. Used methods were not adequate to make reliable conclusions about results of single rounds, pens and animals.