Cow comfort effects on milk production and mastitis: a field study

A field study made by Cornell University shows that second lactation cows showed a significant increase in daily milk production and a decrease in clinical mastitis when a cow brush was installed.


A field study was performed at Sprucehaven Farm and Research Center in New York State, USA. A total of four pens with approximately 100 cows each were used in the study. There were two identical pens of approximately 100 first lactation cows, one with two DeLaval Swinging Cowbrushes (‘Cowbrush’) and one Control pen. The second set of two identical pens housed approximately 100 cows each in second or higher lactation with one pen containing two Cowbrushes and one Control pen.

Daily milk production data were available for a period of approximately 3 months before the go-live date of the Cowbrushes and six months after the go-live date. Mixed model linear regression analyses were performed on the daily milk production data.

The results indicated that second lactation cows showed an approximate 3.5% (1 kg) higher daily milk production while no statistically significant difference (at P<.05) was observed in first lactation or older lactation animals. Clinical mastitis data were collected before and during the field study period. Clinical mastitis was not different between the study pens before the go-live data of the Cowbrushes, however after go-live, clinical mastitis was reduced by 34% (P<.05) in the cows in second and higher lactation in the Cowbrush pen. No difference in clinical mastitis was observed in the two pens with first lactation animals.

In conclusion, installation of the Cowbrushes resulted in either no difference in daily milk production (in lactation 1 and 3 and higher), or in an approximate 3.5% (1 kg) higher daily milk production. Clinical mastitis was lower in pens of cows in second and higher lactation with a Cowbrush present.

Cow with a cowbrush


The DeLaval swinging cow brush provides grooming opportunities for dairy cows. Dairy cows have a high need for grooming as was shown recently in a study using a similar cow brush system (DeVries et al., 2007). Cows in a pen with a mechanical brush increased their grooming time approximately 5-fold compared to a pen without such a brush. The authors concluded that a grooming device helps to satisfy the cow’s need for grooming while at the same time improving cow cleanliness. Both these factors (better ‘welfare’ and cleaner cows) may have an impact on disease occurrence and on milk production.

Studies have associated cow cleanliness with mastitis incidence (Schreiner and Ruegg, 2002), and the increased activity of the cow may lead to less metabolic diseases, better digesting and eventually in higher milk production.

Although the intuitive concept of the swinging cow brush being associated with better productivity and increased health may be straightforward, no hard data exist to quantify this potential relationship. Therefore a comparison study of cows experiencing a cow brush was designed, including a contemporary control and pre-study baseline measurements.

The objective of this pilot study is to compare daily milk production and animal health in pens of cows with and without a swinging cow brush on one New York dairy farm.


In this field study, a total of four pens were used with two pens having two Cowbrushes each installed and two pens that served as contemporary controls. Although many data points provided a very precise evaluation of the differences between the pens with and without the Cowbrushes, the study design is essentially a two by two comparison. This should be kept in mind when further evaluating the observed differences between the pens.

Cows adapted well to the Cowbrushes and utilized the brushes frequently. Farm workers noticed the frequent use of the brushes and the eagerness of the cows to use the brushes.

Daily milk production for second lactation animals showed a significant and increasing difference in daily milk production with the time passing since installation. At approximately 6 months after installation, the difference in daily milk production stabilized at approximately 1 kg higher daily milk production (3.5%) in the cows experiencing the Cowbrushes (Figure 2B). This difference in daily milk production was not observed in the other two lactation groups.

It is not clear why one lactation group of cows would show an effect due to the Cowbrush while other groups do not show this effect. While evaluating the behavior of cows with access to a mechanical brush, DeVries et al. (2007) did not report on differences between parity groups in the use of the mechanical brush. It may be hypothesized that cows that are more active and walk to use the Cowbrush are also inclined to visit the feed bunk while active. Cows being more active would also utilize ketones more efficient and may experience less reduction in feed intake due to high ketones concentration in serum. This would lead to a potential increase in daily milk yield. No obvious reason is present why this would differentially affect cows in different lactation groups. Ketosis registration in the study herd was limited to clinical cases. No difference in clinical cases of ketosis was observed in the Cowbrush and control pens (7 and 6 cases respectively).

Clinical mastitis data in cows in second and higher lactation (pens 27 and 28) showed a clear and significant difference in mastitis incidence as soon as the Cowbrushes were installed. The difference in mastitis incidence increased with increasing lactation number.

We can only speculate with regards to the reasons for this decrease in mastitis cases in the pens with Cowbrushes. The initial hypothesis was that cows that are more active and walk more, are lying a shorter period of time in the stalls and thereby exposing themselves less to bacteria on the stall surface. Also the grooming behavior of the cows may lead to an overall cleaner skin in the animals with access to the Cowbrush. Although the mammary gland itself will not be groomed when using the cow brush, the tail and hind areas of the cows will be groomed (see picture 4 in appendix I) and may result in a lower exposure of the mammary gland due to general reduction of dirt on the cow. No difference was observed in the two pens with first lactation animals. The incidence of mastitis in both of these pens was very low and the power of this study to identify differences in clinical mastitis between the two first lactation cow pens was very small.

In summary, installation of the Cowbrushes resulted in an immediate increase in cow grooming behavior. Installation of the Cowbrushes resulted in either no difference in daily milk production (in lactation 1 and 3 and higher), or in an approximate 1 kg higher daily milk production in second lactation cows. Clinical mastitis was lower in pens of cows in second and higher lactation with a Cowbrush present.

Read the full study here


  1. DeVries, T.J., Vankova, M., Veira, D.M., von Keyserlingk, M.A., 2007. Short communication: Usage of mechanical brushes by lactating dairy cows. J. Dairy Sci. 90, 2241-2245.
  2. Grohn, Y.T., McDermott, J.J., Schukken, Y.H., Hertl, J.A., Eicker, S.W., 1999. Analysis of correlated continuous repeated observations: modelling the effect of ketosis on milk yield in dairy cows. Preventive Veterinary Medicine 39, 137-153.
  3. Schreiner, D.A., Ruegg, P.L., 2002. Effects of tail docking on milk quality and cow cleanliness. J. Dairy Sci. 85, 2503-2511.
  4. Schukken, Y.H., Grohn, Y.T., McDermott, B., McDermott, J.J., 2003. Analysis of correlated discrete observations: background, examples and solutions. Preventive Veterinary Medicine 59, 223-240.

Swinging cow brush SCB DeLaval


Cornell University

Cornell University

Cornell University's mission is to facilitate New York State economic development by increasing the profitability and competitiveness of its dairy industry.

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