The use of antibiotics

The dry period is a crucial time for ensuring good udder health and a healthy start to the next lactation. During the dry period the cow and her udder are preparing for the next lactation, so any problem during the dry period will have a negative effect on the cow’s overall well-being and milk production after calving.

There are two critical stages during the dry period when udder health is especially at risk:

• the first week after drying off
• the week prior to calving

During the first week after drying off, a keratin plug in the teat canal is formed, that works as the udder’s natural defence mechanism to prevent bacteria from entering the teat canal during the dry period. Prior to calving, this plug slowly dissolves in preparation for lactation.

To prevent and reduce infections, you should ensure a low overall infection risk within your herd and barn. A high infection risk arises in one of two ways: from the surroundings or via other cows in the herd.

Conventional dry cow therapy, also known as blanket dry cow therapy, where all cows receive antibiotic treatment prior to drying off is a widely used practice to prevent mastitis in some countries. However, this leads to excessive and often unnecessary use of antibiotics in the herd, and is therefore problematic. You should avoid treating all cows with antibiotics prior to drying off. Selective dry cow therapy can be used to reduce the number of treated cows. Based on cell count and mastitis history you can identify which animals need treatment (cows with cell count >100,000).

Make sure you have a correct mastitis diagnosis when selecting cows for medical dry treatment with antibiotics. The aim is to only treat cows with a good healing prognosis. For cows with chronic mastitis, antibiotic treatment has no effect and to reduce the infection pressure at herd level the best option is to cull any such cows.

Dry cow treatment with antibiotics has two aims:

• To protect against new infections during the first part of the dry period (in particular a problem when drying off)
• To help combat existing infections

Data from treatments show that medical dry treatment (antibiotics) alone or in combination with other measures lead to:

• Fewer new infections for cows that were healthy before drying off
• More cases where infected cows are cured and begin lactation with a healthy udder

A well-founded adjustment of your dry-off management will result in a reduced use of antibiotics without an increased risk of mastitis in your herd.

Source: SEGES, Denmark