Experiencing any one of the metabolic diseases of dairy cows, such as milk fever, ketosis, and displacement of the abomasum, is strongly associated with decreased fertility in the cow. These metabolic problems in the transition dairy cow can have a tremendous negative effect on the immune system of the cow, increasing her susceptibility to retained placenta (RP), metritis and endometritis. A strong immune system is also required if immune recognition of a conceptus is to occur so that implantation can proceed.

Research on the nature of these diseases has shown:

• Cows with hypocalcemia (milk fever) are 3.2 times more likely to also have RP, compared to cows with no hypocalcemia. Hypocalcemia also has been linked to a higher incidence of mastitis and endometritis in postpartum cows.
• RP has been shown as a risk factor for developing ketosis, and ketosis is a highly correlated risk factor for the development of metritis and mastitis.
• Cows with RP, metritis and endometritis have been shown to have impaired neutrophil (white blood cell) function up to two weeks prior to calving, before lactation starts and before any bacteria can enter the uterus.
• Similarly, levels of non-esterified fatty acids (NEFA) have been shown to be elevated in cows that eventually developed metritis at least two weeks before they calved. This suggests they were mobilizing fat even before calving.

Negative energy and protein balance in the late dry period likely impairs immune function and leaves cows less equipped to manage the stress, bacterial invasion and metabolic changes that occur during calving. For example, it is likely that RP does not necessarily “cause” mastitis or metritis, but is symptomatic of a depressed immune system overall.

If we are going to reduce uterine disease, we must look back to the dry cow. To improve feed intake in the critical period around the time of calving, we must offer palatable rations in a cool, uncrowded environment with plenty of bunk space (28″ to 30″ per cow) to encourage intake. Clean maternity pens, clean obstetrical equipment when assisting calving and clean stalls can reduce exposure to bacteria; even a strong immune system can be overwhelmed by a large bacterial load in the uterus.

Feed to avoid metabolic disorders. Reducing dietary potassium in the dry cow ration and adding chloride or sulfate to the diet in a palatable form to reduce hypocalcemia improves feed intake in early lactation and helps keep white blood cells functioning. Maintain adequate fiber in dry and fresh cow diets to avoid displaced abomasum. Keep cows from getting too fat, as fat cows seem to suffer the greatest decline in feed intake prior to calving.

To read a more comprehensive summary of the author’s insights on the relationship between immunity, transition-cow immunity and reproductive performance, follow this link.