Dairymen often debate the best method to dry off cows. There are two common methods used to dry off cows. They are 1) immediately stop milking the cow and dry treat the cow, and 2) intermittent milking plus sometimes feeding only hay for 7 to 14 days. The National Mastitis Council (NMC) recommends that high producing cows should be taken off concentrate feeding for fourteen days prior to dry off. This is followed by abrupt cessation of milking and dry cow treatment. NMC published this recommendation in a fact sheet titled Drying Off Cows (www.nmc.online.org).

The research data for the recommendation was not given. Dr. R. Dingwell and co-workers published a very good paper on factors involved in drying off cows (NMC 40th Annual Meeting Proceedings, 2001 pages 69-79). Dr. Dingwell presents a good review of the literature and lets us know that the best method to dry off cows is still controversial. The research evidence is not clear.

Several things do appear to be true based on available research. There is good evidence to show that the greatest reduction in milk yield is achieved by intermittent milking. Restriction of feeding grain helps to reduce milk yield. Cows that are producing less milk at dry off have less new intramammary infection (IMI) during the dry period caused by either major or minor pathogens. It has also been proven that cows producing less milk have higher concentrations of inhibitory factors and phagocyte cells in their udder.

Dr. Dingwell studied official milk test records (DHI) on over 30,000 cow lactations between January, 1998 and December, 1999. He examined the relationship between level of milk production at dry off verses new IMI at the start of lactation. He used milk weights at the last month before dry off. He compared milk weights with somatic cell counts (SCC) the last month before calving and the first month after calving. A new IMI was defined as a change in linear score from less than 4.0 at last test prior to drying off to a linear score greater than 4.0 at first test in the next lactation. This has been recommended as a reasonable threshold to detect subclinical mastitis. The results revealed that 26% of cows producing greater than 21 kg. of milk at dry off developed new IMI compared to only 16% of cows producing less than 13 kg of milk. This difference was statistically significant (P< 0.05).

DHI data gives us an indication of the percent of new IMI. However, to be more precise, milk samples should be obtained and cultures performed at dry off and calving. Other important factors such as udder involution, closure of the teat streak canal, and management practices of each herd need to be studied. Dr. Dingwell and others have recently organized a large study to evaluate the affect of level of milk production at dry off on new IMI. They have enrolled herds in Canada, New York, Iowa, and Kansas.

Dr. Dingwell concludes that much more research is needed to determine the best method to dry off cows. He emphasizes that we should continue to promote the importance of dry cow antibiotic therapy and proper teat disinfecting and cleaning. Dr. Dingwell also emphasizes that the ability to implement various dry off procedures in a given herd will vary depending on the facilities, available labor, and management structure of the dairy.

Comments by Dr. Whitmore:

I agree with Dr. Dingwell's comments that facilities sometimes dictate the choice of dry off procedures. It is easy in our barns to create a group of cows and feed only hay for two weeks. But it is difficult to move that group so the pen can be cleaned and the stalls bedded and still keep normal milk cow flow going. So we do not restrict feed intake of our cows prior to dry off. We also do not do intermittent milking. We stop milking and dry treat. It may not be the best way but it seems to be working okay.