One of the reasons is that the average days in milk are too high. When the average days in milk go up from 180 days to 200 days the average production per cow will decrease with 2 Kg. Calculate this on a herd size of 500 cows and it will show you the importance of the average days in milk on a large dairy farm. A high average DIM is caused by poor fertility. And a mean reason for a poor fertility is an inadequate transition management.

Also the beginning of the dry period and the start of the new lactation is the period that the cow is the most vulnerable for mastitis.

A third reason for the importance of the transition period is that too many cows have to leave the herd before 60-90 days in milk. The mean reason for this culling are metabolic problems.

We have to realize that for the high producing cow this period is very essential while many chances in the animals live show up in these weeks.

The term transition is to underscore the important physiological, metabolic, and nutritional changes occurring in this time frame. It constitutes a turning point in the productive cycle of the cow from one lactation to the next. The manner in which these changes occur and how they are managed are of great importance as they are closely linked to lactation performance, clinical and subclinical postpartum diseases, and reproductive performance that can significantly affect profitability.

In traditional point of view people define the transition period is 21 days pre- and post-calving. But in AVA point of view this period is much bigger and start from Dry-off group (1-2 weeks before dry period) and finish when the cow leave Fresh group at 14-21 day after calving. It is important to enlarge the length of transition period, because already at the moment of drying-off the cow we can prevent many metabolic issues.

In this period, the following chances take place in the cows metabolism: