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Calf & Heifer Adviser Articles
Scours caused by variety of pathogens
One of the reasons why calf scours is such a challenging disease for producers is that it can be caused by a combination of two or more pathogens.
“There are four major pathogens that cause calf scours, and a host of minor ones,” said Jerry Olson, senior veterinarian with Pfizer Animal Health. “In most cases, more than one of the causative agents is involved in clinical scours.”
He added that diagnosis of the pathogen(s) involved in scours is challenging because the causative agent may no longer be present by the time the sample is collected and tested at a diagnostic laboratory, and some scours organisms also may be present in healthy calves. Postmortem exams also can be unreliable because dead animals often have intestinal bacterial overgrowth and/or postmortem tissue destruction.
Olson noted some of the characteristics of major scours pathogens:
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Escherichia coli K99 should be suspected as a cause of scours in calves during the first week of life.
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Rotavirus serotype G6and rotavirus serotype G10 also can surface in the first two weeks of life, but may be involved in animals a month of age or older. Infections involving either serotype of rotavirus often cause animals to have profuse watery diarrhea because the absorptive capacity of the gut is markedly reduced when the intestinal villi are blunted.
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Coronavirus usually causes more severe scours outbreak than rotavirus because it affects both the small and large intestine whereas rotavirus affects primarily the small intestine. Coronavirus primarily affects calves from one to three weeks of age. However, like rotavirus, it may occur any time during the first month of a calf’s life and beyond.
Both rotavirus and coronavirus are hardy organisms that can survive for months in moist, cool conditions.
Scours treatment is a frustrating proposition. “Infected animals very quickly have problems with nutrient malabsorption, excess secretion of fluids and intestinal inflammation,” Olson said. “Once these factors start to snowball, their combined effect is difficult to overcome.”
Olson advised that prevention is the most efficient approach to managing scours. Passive immunity created by vaccinating the dam and getting adequate quantities of high quality colostrum from these vaccinated cows shortly after birth are very effective in preventing diarrhea caused by E. coli, rotavirus and coronavirus.
Ideally, for maximum protection of the calf, vaccination of the dam should take place far enough ahead of the “colostrum concentration” window that high levels of antibodies are present in the blood at its onset, he says. This starts at about three weeks before calving, and peaks during the last two weeks before calving. This means that cows need to receive a booster at least three weeks prior to the IgG concentrating period.
Source: Pfizer Animal Health
Add colostrum to milk for gut protection
Colostrum at birth is essential for passive transfer of immunity to calves, but colostrum may also be beneficial in helping older calves fight of intestinal disease. Speaking at a Land O’ Lakes/Purina Feed dairy veterinary meeting, Amelia Woolums, veterinarian at the University of Georgia, says colostrum added to milk to may provide local protection in the gut from intestinal pathogens.
“Maternal antibodies are only present in the gut for a few days; though, when serum antibody levels are high, they can be secreted back into the intestine from the bloodstream,” Woolums explains. “If you have antibody present in the gut that can bind the pathogens before they can stick, you should be able to decrease or prevent disease. Antibody-rich colostrum added to the milk can supply antibodies to bind to those pathogens before they attach to the gut wall. If we put a little colostrum in the calf’s milk every day, it may help protect against some local infectious such as rotavirus, coronavirus and Cryptosporidia.”
Woolums suggests about a 1 percent colostrum-to-milk ratio for as long as two to four months.
Source: Bovine Veterinarian (sister publication to Dairy Herd Management)
Heifers and mastitis
Replacement heifers are critical to herd productivity because they represent the future milking and breeding stock in all dairy operations. Unfortunately, most producers regard young heifers as uninfected, and the presence of mastitis is not observed until freshening or until the first clinical flare-up in early lactation. Thus, animals may carry intramammary infections for a year or more before they are diagnosed with mastitis. The greatest development of milk-producing tissue in the udder occurs during the first pregnancy, so it is important to protect the mammary gland from mastitis pathogens to ensure maximum milk production during the first lactation.
How do heifers contract mastitis? No one knows for sure. However, sources may include:
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Bacteria that are the normal flora on udder skin, which are in an opportunistic position to colonize the teat end and enter the teat orifice
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Bacteria harbored in the oral cavities of calves, which suckle other calves
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Bacteria present in the heifers' environment, such as those found in soil, manure, and bedding material
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Bacteria present on biting flies that congregate on teat ends
Normal flora would be almost impossible to control, as these microorganisms are naturally found on the udders and teat skin. Daily teat-dipping might reduce bacterial populations, but this practice would be highly impractical. The transfer of mastitis-causing bacteria through cross-suckling of calves fed mastitis milk can be prevented by housing calves in individual hutches, and this management practice has become fairly routine. As with attempts to control normal udder flora, the control of environmental mastitis-causing bacteria has its limitations; however, the percentage of intramammary infections caused by environmental streptococci and coliforms in heifers is low, except just prior to freshening. Flies have certainly been implicated in the spread of mastitis-causing bacteria among heifers and should be a major focus of control.
This information was taken from the article "Mastitis Detection, Prevention, and Control in Dairy Replacement Heifers" (S.E. Nickerson and W.E. Owens).
Source: NMC (formerly the National Mastitis Council)
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