Keep tabs on heifer mastitis

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Dairy heifers are often the forgotten animals on the farm until they calve. But, paying attention to their housing and hygiene during pregnancy can influence whether or not they may get mastitis before they ever have a calf. “Unfortunately, it’s still true that producers may have the perception that heifer mastitis is not a problem,” says Steve Nickerson, PhD, University of Georgia.

The highest-risk period of time for heifers to be exposed to mastitis-causing bacteria is after puberty when glands start to develop and produce secretions, which will support growth of bacteria. Steve Oliver, PhD, Univer-sity of Tennessee, says the prevalence of intramammary infection can be high in breeding age, pregnant and early-lactation heifers. “IMI can persist for long periods of time, can increase somatic cell count, impair mammary- gland development and may decrease milk production,” says Oliver.

When infection happens
It’s been shown that the prevalence of heifer mastitis is highest in the last trimester of pregnancy (Fox, 1995). There are several reasons this may happen. Seasonality may be a part of it. Oliver says infections are higher in summer, next highest in the spring, then in the fall and winter, respectively.

 

Single-calf housing that is frequently moved can help prevent early exposure to mastitis-causing pathogens.

Nickerson says warm weather that brings on flies and higher ambient temperatures along with humidity are conducive to bacterial growth in the environment and on heifers’ teat skin. “Also, pasturing heifers with older, infected cows may enhance cross infections, especially in warm seasons when flies can serve as vectors.”

Jim Brett, DVM, Macon County Veterinary Hospital, Montezuma, Ga., adds that in Georgia, there are always more cases in the summer through early winter due to hot weather and a lot of flies. “The ones with fly/teat end damage we may not see clinically until October or November, but they were probably induced in late summer.”

Nickerson adds that many heifers -- sometimes greater than 50% -- can become infected at the same time. Brett notes that he has not seen an incidence rate over 10-15% in a group showing “clinical signs” at a common time, but there may be several subclinical cases that become clinical later. “This promotes the quandary: If you have a high clinical incidence, do you treat only the individuals or the whole group?” he asks.

Brett agrees that the most common time to find clinical mastitis is in springers and adds that the next most common time is pre-breeding (10-15 months), and, “at least we find them when they’re brought up for breeding, which is a neglected group.”

Examining heifers
Heifers can be examined during a variety of growth phases and when herd management practices allow, such as during AI, pregnancy check or hoof trimming. Nickerson looks for abnormal appearance and consistency of secretion and occasionally hard, indurated quarters.

Coagulase-negative Staphylococcus (CNS) is the most prevalent organism in these third trimester mastitis cases. However, Staphylococcus aureus, E. coli and Streptococcus can also be found.

Culturing is not routinely done for heifer mastitis, mainly because of the expense. “It’s impossible to get owners to do it,” Brett says, “and since our clinical cure rate has been so good, they ask, ‘Is it really necessary to spend the money, and then what do we do differently as a result of identifying the organisms?’”

 

Steve Nickerson, PhD, says many producers don’t realize heifer mastitis can be a problem.

Brett says 90% of the time only one quarter is infected, but more than one quarter can be infected at the same time. “Aggressive treatment for a minimum of seven days has clinically cleared 90% of the cases,” he says. “If they don’t respond to a second week of treatment with a different antibiotic, tube and injection, they don’t ever clear.” Nickerson adds that infections can persist for a year or more.

Severe infections resulting in blind quarters can also result in heifers being culled. Nickerson says early detection, even of a severe S. aureus case, can respond favorably to treatment if treatment is done well before calving and with dry cow therapy.

Some of Brett’s clients will calve out heifers that have had severe infections and milk them as three-quarter cows and see how well they produce before making culling decisions.

 

Jim Brett, DVM, checks for mastitis in pre-breeding heifers -- an often negelected group.

Risk factors
Nickerson notes three important risk factors: “Fly control is critical. Do not allow heifers to suckle one another, and use separate hutches.” Along with that, Brett suggests for baby calves single-calf housing that is frequently moved, and never feeding calves mastitis milk.

Though Brett’s clients have heifers on pasture, they have fly problems in low areas, wet areas around feed and water troughs and other contaminated areas that draw flies. Another risk factor he notes is overcrowding, which leads to contaminated bedding and more fly problems. (See risk factors sidebar.)

Many of the risk factors can be controlled with a clean environment and fly control, but other methods may not work as well. Oliver notes a study in which two quarters of heifers were teat-dipped three weeks before calving, three times per week with a 0.1% iodine barrier dip. Despite the dipping, Oliver says there was no difference between dipped and control quarters and no improvement in udder health.

Treatment
Heifers respond better than cows to the treatment of S. aureus using dry cow therapy, 95% and 65%, respectively, says Nickerson.

 

Steve Oliver, PhD, says IMI can be high in breeding age, pregnant and early-lactation heifers.

Oliver found that lactating cow therapy seven to 14 days pre-calving was effective in eliminating many intramammary infections during late gestation (Oliver 1992, 1997, 2003), especially those caused by CNS.

“If you treat these infected heifers and basically allow them to calve uninfected,” explains Oliver, “during the entire lactating period up to the time of dry off, the difference in magnitude between heifer mammary quarters and isolated pathogens in controls versus treated animals is huge, and it’s maintained throughout the entire lactation.”

One distinct disadvantage, however, to lactating cow therapy pre-calving is the potential for antibiotic residues in milk. Oliver says 85% of colostrum samples from animals treated with cephapirin seven days before expected calving were positive for residues in milk. At the sixth milking (or the time that milk was likely to go into the bulk tank), 28% percent of samples obtained still contained residues. “That’s totally unacceptable, even if the antibiotic is effective at eliminating infections,” says Oliver.

However, a subsequent study by Oliver demonstrated that when heifers were treated with cephapirin 14 days before calving, only four of 127 samples (3.1%) obtained from cephapirin-treated mammary quarters at the sixth milking after calving were positive -- and three of the four positive samples came from a heifer that calved within three days of treatment. Results of this study showed that intramammary infusion of cephapirin earlier in the prepartum period reduced the occurrence of residues in milk during early lactation without impacting treatment efficacy.

Nickerson says, however, that use of lactating cow therapy using one infusion at one to two weeks prepartum cannot be expected to cure S. aureus infections --- these must be treated with dry cow therapy during pregnancy, says Nickerson. However, on a practical basis, Brett adds that producer compliance in treating these animals prepartum is poor.

If the udder is not severely inflamed, Brett uses intramammary dry cow tubes when he finds clinical cases of heifer mastitis. All cases also receive systemic antibiotics. “We use the long-acting forms to limit treatments to every two or three days,” he says. “Treatment for at least seven days is advised and medications are changed after that seven-day period if they are not responding.”

Key points about heifer mastitis

Steve Oliver, PhD, offers these keys points about heifer mastitis:

  • It occurs frequently in breeding age, pregnant and early-lactation heifers.
  • Many intramammary infections persist, causing increased somatic cell counts, impairing mammary development and decreasing production.
  • Several risk factors have been identified.
  • Prepartum antibiotic therapy is an effective strategy to control heifer mastitis.
  • Oliver’s studies show that antibiotic-treated heifers produced significantly more milk with lower SCC than controls, making it very cost-effective.
  • Residues in milk can occur if heifers calve early.
  • Milk should be tested before commingling in the bulk tank.

 

Poor and crowded calf housing can contribute to heifer mastitis.

Risk factors for heifer mastitis

  • High herd SCC
  • Staphylococcus aureus and Mycoplasma
  • Absence of fly control
  • Summer calving
  • Feeding calves mastitis milk
  • Calves and cows contact
  • Absence of heifer antibiotic therapy
  • Poor housing conditions
  • Milk leakage
  • Udder and teat edema
  • Pathogens on body sites
  • IMI at calving increases risk of infection during lactation
  • IMI at calving increases risk of clinical mastitis in first week of lactation
  • Mastitis near calving increases risk of further cases of mastitis and culling during first 45 days of lactation

Source: Martin-Richard, 2001


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