Body condition score and its association with dairy cow productivity, health, and welfare.

Discipline: body condition score; Keywords: body reserve status, fat, hormonal changes, pregnancy, metabolic disorders.

Research in this context was reviewed by J.R.Roche and coworkers in a paper published in the Journal of Dairy Science, Volume 92, pages 5769 to 5801. The title of the paper is: Body condition score and its association with dairy cow productivity, health, and welfare.

Body condition score (BCS) in the past 50 years has been considered more reliable than body weight as a management tool to assess the status of the dairy cow, since it is well-correlated with body reserves and the mobilization thereof for milk production. Mobilizable reserves consist primarily of fat and correlations between dissected fat and BCS are in the order of 0 75 to 0.9. However, correlations with between and intra-muscular fat are less convincing, which illustrates that BCS will not be reliable under all conditions of a changing metabolic environment of the cow, unless we can define or determine all influencing factors and can put these in prediction models. This has been the subject of many studies reviewed in this paper.

It is known that the reliability and consistency of scoring is influenced by many factors, amongst others the assessor, genetics, level of production, stage of lactation, intercalving period, the nadir between 40 and 100 days after calving, whether a TMR is fed or the feeding system is pasture based (reflecting changes in pasture quality with season), pre-calving condition, health etc. Overall the manager is concerned about maximum or optimum milk yield, optimum reproduction, low level of metabolic and other diseases and cow comfort and well-being. The question is how all these relate to BCS in order for this subjective tool to become even more useful.

Summarized, the results show that management and feeding have little effect on BCS loss one to 4 weeks postcalving, because metabolic and hormonal changes from non-lactating to lactating drive the process. The BCS in which a cow calves, nadir BCS and the amount of BCS the cow loses postcalving are strongly associated with milk production, reproduction and health, whereas BCS is also correlated with animal welfare and how the cow "feels", but less convincing. In more specific terms, although the correlations vary, there is relative consistency in the associations among calving and nadir BCS, and BCS change on milk production, postcalving anoestrus, the likelihood of a successful pregnancy and days open, the risk of uterine infection and the risk of metabolic disorders. For most factors, the association with BCS is not linear, implying that there is an optimum. The optimum for calving is 3.0 to 3.5 if the 5-point scale is used; lower calving BCS is associated with lower production and reproduction, whereas calving BCS of more than 3.5 is associated with a reduction in early lactation feed intake and milk production and an increased risk of metabolic disorders. With extended computer capacity, new technologies involving laser and digital photography, and multi-factor models, the use of BCS as a useful management tool is expected to increase in future.

Bottom line: There is convincing evidence that if farmers and managers aim for a BCS of 3.0 to 3.5, most of their objectives in optimizing milk production, reproduction, health and cow comfort will be met. This is not to say that optimization of particular issues does not fall outside this range, but further evidence to that effect is required.