Ultrasonographic assessment of body condition in dairy herd management.: Part 3:: Evaluation of reference values

The target of this study was to identify an optimal conditional range to be used in dairy herd management which combines high milk yield with acceptable fertility traits. For this purpose, backfat thickness (BFT) was evaluated at 46111 cows on 78 different dairy farms. By polynomial regression analyses reference curves were computed for the development of body condition in course of lactation and for the daily change of BFT with cows being measured twice. Mean body condition in the dry period should range between 22 and 23 mm BFT. Body fat loss in early lactation should be terminated at about 90 days in milk with a conditional nadir of 13 mm BFT on herd average. At drying off, animals should have regained calving condition. However high producing dairy cows have to gain body condition moderately in the dry period.