Mastitis in dairy heifers

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Heifer mastitis has been researched since the 1980s when it was noticed that many heifers were freshening with clinical mastitis.

“Studies of breeding age animals revealed that intramammary infections (IMI) may be diagnosed as early as 6 months of age, and infections persist throughout pregnancy and into lactation,” says Steve Nickerson, PhD, University of Georgia.

Other studies demonstrated that greater than 90 percent of breeding age and bred heifers (12 to 24 months of age) may be infected. Most of the infections were shown to be caused by the coagulase-negative staphylococci (Staphylococcus chromogenes and Staphylococcus hyicus) followed by Staph. aureus (20 percent). Mixed isolates of coagulase-negative staphylococci (CNS) and Streptococcus species were also found.

“We have always focused mastitis control on mature cows,” Nickerson states. “However, we ignore the first half of her life when she could have mastitis as a heifer. If the average age at calving is 2.5 years, and a cow lives for 5.5 years and has three lactations, then for 45 percent of her lifetime, no mastitis control is being applied.”

In some herds, S. aureus mastitis prevalence in unbred and bred heifers serves as a source for infecting the milking herd. IMIs in young dairy animals are associated with local inflammation, induration, and extremely high somatic cell counts (SCC). Furthermore, histological analyses have shown that Staph. aureus infections adversely affect the development of milk-producing tissues of heifers.

Nickerson suggests examining heifers for signs of mastitis either at the time of AI or preg check when they are being handled anyway. Visual and manual examination of the developing udders, mammary fluid and teat skin will help identify swollen quarters, abnormal secretions, and presence of teat scabs. Individual swollen quarters with abnormal secretions (clots and flakes) and those with teats exhibiting scabs and abrasions are most likely to be infected and should be treated.

Because of the high level of infection commonly found in heifers at some dairies, especially mastitis caused by Staph. aureus, infected quarters should be treated. The testing of various staphylococcal isolates obtained from heifers for susceptibility to antibiotics commonly incorporated into mastitis infusion tubes has shown that antibiotic resistance is usually low.

“Ideally, infected heifers should be separated from uninfected heifers as flies do spread the disease,” Nickerson says, “however, from a management standpoint that is really difficult to do.”

Read the full article on heifer mastitis in Bovine Veterinarian here.



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