Dairy cows are most susceptible to new intramammary infections (IMIs) during the dry period. Cows are at greatest risk two to three weeks after dry-off and two to three weeks prior to calving.

New IMIs acquired during this timeframe result in “carryover infections” into the next lactation, which lead to an increased risk of clinical mastitis cases, inferior milk quality, production losses and early herd removal. Prevention can have a significant impact on a dairy producer’s bottom line. Clinical mastitis cases during the first 30 days of milk have been estimated to cost more than $400 per cow.

Three dry cow strategies that can help reduce IMI risk in the dry period include reducing bacterial exposure at the teat end, use of dry cow treatment and enhancing host and udder immune defense mechanisms.

Reduce bacterial exposure at the teat end

Dry cows and springing heifers should be kept clean and dry to maintain cow comfort and minimize bacterial exposure. Mastitis-causing bacteria, such as coliforms and environmental streps, are shed in manure in large numbers. These bacteria quickly contaminate the dry cow environment, particularly if there is overcrowding or warm environmental conditions.

Provide adequate resting space with loose housing and keep freestalls clean, dry and well maintained to lower bacterial numbers. Adequate ventilation and heat abatement help improve dry matter intake (DMI); control heat buildup, moisture and humidity; and further reduce bacterial counts.

Use of dry cow treatment

Infusion of dry cow treatment (DCT) at dry-off is a well-established management practice intended to cure existing subclinical IMIs and help prevent new infections. Published studies have shown that approximately 95% of cows subclinically infected at dry-off are infected with gram-positive bacteria (environmental staphs and streps), and less than 5% are infected with gram-negative bacteria (coliforms). Because gram-negative infections usually self-cure during lactation, gram-positive infections are the target for DCT. An ideal choice at dry-off is a treatment that targets and has been shown to be highly effective against gram-positive bacteria.

Enhance host and udder defense mechanisms

Optimizing immune function is critical for cow health. Overcrowding during the dry period not only results in more manure within the pen, which increases mastitis risk, but it also impacts bunk space and bed space availability. Eating space is more critical. Inadequate intake pre-calving must be avoided, as negative energy balance before calving can lead to fatty liver, ketosis and infectious diseases such as mastitis post-calving. Clean, fresh, available water is also vital for cow health.

Teat-end condition is also a risk factor to develop a new IMI in the dry period. Hyperkeratosis predisposes teats to bacterial colonization. In addition, teats that are cracked are 1.8 times higher risk of acquiring a new IMI during the dry period.

Many high-producing cows are also vulnerable to a new IMI in the dry period because of a delay or failure in formation of an adequate keratin plug. The keratin plug forms in the teat canal during the dry period and is the cow’s natural defense against bacterial invasion.

To help combat these teat-end risk factors, internal teat sealants are infused into the teats at dry-off to simulate the keratin plug. A malleable paste, sealants function as an inert internal physical barrier to help prevent bacterial invasion during this timeframe. Studies have shown that, used with or without DCT, an internal teat sealant helps reduce the risk of a cow developing a new IMI during the dry period.

We can also raise immunity to gram-negative mastitis pathogens through strategic vaccination. Core antigen vaccines are labeled to aid in reduction of mastitis due to E. coli, when administered at dry-off, pre-fresh and in early lactation. To provide maximum protection against clinical coliform mastitis during the highest risk period – the first 100 days after calving – three doses of vaccine at four- to six-week intervals are recommended.

There is variation in endotoxin levels between competitive core antigen vaccines. Endotoxins are released from the outer bacterial cell wall during the manufacturing process of gram-negative vaccines. Endotoxins can cause fever, lack of appetite, depression, shock, abortion and even death. Look for a vaccine specially formulated to be low in endotoxin. Our vaccines print the endotoxin level on the bottle to assure you of product safety.

Consult with your veterinarian to create a dry cow management program that minimizes bacterial challenge, utilizes DCT and maximizes herd immune defenses during the dry period.

—Submitted by Boehringer Ingelheim Vetmedica