It was thought that cows with a very high milk production were more susceptible to disease due to the extra demands placed on their bodies. To test this idea Esther Kornalijnslijper infected the udders of a number of cows with the bacterium E. coli, which causes mastitis. She then studied how long it took before the pathogenic organisms had disappeared from the cows' bodies. She found no difference in the disease progression between cows with a high milk production and cows with a lower milk production.
A total of 36 dairy cows were infected for the purpose of this study. Based on their production in the previous lactation period, the researcher selected 18 high-producing cows from the herd at the experimental farm at the Institute for Animal Science and Health, Lelystad. She complemented this group with 18 cows from the experimental farm at the lower end of the production hierarchy. During the three weeks prior to calving and the 3 weeks after calving, Kornalijnslijper regularly took blood and milk samples to follow the progression of the disease.
Much to her surprise, both groups exhibited the same disease progression. Therefore Kornalijnslijper concluded that resistance to mastitis in the high-production cows was not directly affected by their high milk production.
With this conclusion the researcher certainly does not call for the unlimited increase of milk production in cows. Many other aspects also play a role in this discussion, such as the nutritional state of the cows on the farm. During the experiment the cows were fed on an individual basis and they therefore all received good feed in sufficient quantities. This cannot always be realised in everyday practice.
Also this study only measured the immunity of the cow and not her welfare. Therefore, it is particularly important that ethical and welfare questions are posed at the forthcoming symposium.
For further information please contact Esther Kornalijnslijper, tel. 31-302-537-551, 31-302-949-581 or 31-654-677-298, e-mail: j.e.kornalijnslijper@vet.uu.nl. Esther Kornalijnslijper will present her results on 10 April 2003 during the symposium 'Limits to Animal Welfare and Production' that will be held in Utrecht.
This symposium will be held on 10 and 11 April 2003 at the Boerderij Mereveld in Utrecht. Thursday 10 April 2003 will consider mainly the scientific aspects. Friday 11 April 2003 is the public day, where plenty of attention will be devoted to societal themes. For further information please contact Annemieke van der Kooij (Netherlands Organisation for Scientific Research), tel. 31-703-440-866, e-mail: kooij@nwo.nl or on the Internet: www.dierenwelzijn.info.
The research is being funded by the Netherlands Organisation for Scientific Research.