Mastitis Effects on Reproduction

Mastitis is the inflammation of the mammary gland, which is usually correlated with intramammary infection (IMI) by bacteria or fungi, being the first more common. Clinical mastitis is manifested by secretion of abnormal milk (i.e. watery milk, presence of flakes in milk, etc.) and/or inflammation (i.e. redness, swelling, hardness, etc.) of the mammary gland. Because it is accepted that the normal mammary gland has somatic cell count (SCC) of less than 200,000 cells/mL (linear somatic cell count, LSCC, less than 4) and no bacterial infection, in many circumstances, cows that have SCC greater than 200,000 cells/mL (LSCC > 4) and/or bacteria in the milk, but do not have clinical signs of mastitis, are considered to have subclinical mastitis. The costs associated with mastitis are innumerous and include antibiotic treatment, milk discarded, reduced milk quality (i.e. increased somatic cell count), increased culling rates, and reduced milk yield. Another cost that incurs from occurrence of mastitis that is often taken for granted, however, is reduced fertility. Although a direct causal effect of mastitis on reproductive inefficiency has not been established, it is evident that a correlation between mammary gland health and fertility of lactating dairy cows exists.