Neonatal mortality is a major cause of economic loss in beef cattle herds. Exacerbating the problem is the fact that the young calf is an efficient amplifier of pathogens.
Bob Larson, DVM, PhD, Kansas State University, says young beef calves are generally exposed and infected by fecal-oral pathogens such as rotavirus, coronavirus, Cryptosporidia and Coccidia while they are still very young. “In addition, most will be infected with infectious bovine rhino-tracheitis (IBR) and bovine viral diarrhea virus (BVDV) while they are still suckling,” Larson says.
John Groves, DVM, Livestock Veterinary Service, Eldon, Mo., says in his practice pathogens associated with enteric disease contribute to the majority of health problems in young calves. “Depending on how much I choose to spend on diagnostics, I can document almost all of the pathogens associated with neonatal scours,” Groves says. “Once in the throes of a disease outbreak, E. coli seems to be most often involved by the time we start losing calves.”
Infectious bacteria, viruses and protozoa are shed by clinically ill calves, healthy adult cattle and subclinically infected calves. Sick calves will shed pathogens in large quantities, causing considerable environmental contamination. Control strategies for neonatal health include limiting the exposure of young calves to older calves, which serve as reservoirs and amplifiers of infectious disease agents, and dispersing young calves to maximize hygiene (see Sandhills Calving System).
Calves amplify disease because as maternal (passive) immunity wanes as active immunity builds, calves have a window of time in which they are at increased risk of infection and haven’t built enough active immunity to stem the tide of pathogen amplification. “There are usually other sub-populations of calves around that are ready to take over as secondary amplifiers, such as new calves born into a pasture where we are already having scours problems,” Groves says. Add to that animal density, stress and environmental factors, and disease multiplies.
By 12 hours after birth, the ability to absorb antibodies from colostrum decreases drastically, eventually ceasing between 1 and 2 days of age. Larson says that calf serum IgG concentrations less than 1000 mg/dL are associated with increased morbidity, increased mortality and decreased performance.
“It has been well demonstrated that failure of passive transfer and other factors which affect colostrum quality have a life-long impact on health as well as productivity,” Groves adds. “On most of the ranches I work with, neonatal scours challenge is the greatest and is exacerbated by risk factors which affect colostral quality and good colostral transfer.”
Calves born unassisted have greater antibody absorption. A difficult birth that does not result in calf death, but prevents either the cow or calf from standing in a timely manner, can serve as a negative result of dystocia, Larson notes. “Even when fresh colostrum is obtained from the dam and administered by bottle to calves that survive a difficult birth, the amount of absorbed antibodies may be decreased.”
Groves stresses management practices to his beef producers to enhance the chances for successful passive transfer of high-quality colostrum. They include pre-calving vaccination against calf scours pathogens, low-stress handling at calving time, cattle managers who are prepared to assist a calf if it has not nursed within a few hours of birth, and sometimes the use of colostrum supplements in an outbreak situation.
Calves and respiratory disease
Larson occasionally sees sporadic respiratory disease outbreaks in calves nursing cows, and the herd prevalence can get very high (i.e., 30-40% of calves). Groves implicates year-round calving for respiratory disease challenges in some of his herds. “I think calves born into those circumstances tend to face a different set of risk factors and disease challenge,” he says. “I believe young calves in these herds are exposed to higher levels of respiratory pathogens because of older calves in the population. In these herds, we monitor young calves closely for BRD, and outbreaks are not unusual.”
Limit pathogen exposure
Another important factor in calf morbidity and mortality is the amount of pathogen exposure. Sanitation, protection from inclement weather and other stressors, and separation from sick calves will decrease the risk of morbidity and mortality of calves.
“Any procedure that concentrates large numbers of cattle in a small area increases environmental contamination and, consequently, increases the potential for fulminant outbreaks of neonatal disease,” Larson explains. “Extensive systems in which calving cows are dispersed in large calving pastures are generally considered optimal from the perspective of reduced disease transmission between neonatal calves.”
Cows will tend to congregate around feed and water sources, and these areas may become heavily contaminated. If supplemental hay and grain are fed, these should be provided at locations that are both separate and distant from water sources to encourage cow dispersal and minimize contamination, and should be moved or spread out frequently.
The calving area should be free of mud and should be protected from the wind. A large pasture with good drainage, southern exposure and a natural windbreak (sufficiently large to avoid concentration) that will block prevailing winds is probably adequate for many mature herds.
The ability to dry and warm calves that have been born during inclement weather becomes critical for high survival proportions during snowstorms or rainstorms accompanied by low temperatures. Only those heifers and, less frequently, cows that require assistance during parturition or to establish a bond with their calf should be confined to a calving barn or small pen.
Keep good records
Accurate records will permit practitioners and producers to base their calving management strategies on fact rather than perception. “Often we are hampered in an investigation when approximate calf ages and other information is not known or transferred to the veterinarian,” Larson states. “Getting as much information on any calves that die or require treatment allows the veterinarian to look for risk factors such as age at disease onset, age at death and age of dam.”
With some of his producers, Groves manages a set of production records which allows him to better define the relationship between risk factors and certain outcomes such as the risk of becoming sick, risk of death, medicine cost per head and impact on production parameters like weaning weight.
Cow-calf records management is an important part of Groves’ practice. “I believe the future of food animal medicine depends on records and data management,” Groves says. “Production records are requisite for the practice of production medicine, and successful cattle production depends on production medicine.”
Nothing is worse for your client than having a nice crop of calves on the ground, then suddenly dealing with an outbreak. John Groves, DVM, says an outbreak of calf scours is an extreme challenge for both producers and veterinarians. “When things get under control, it’s time to start planning for next year’s calving season and ways to avoid another outbreak,” he says.
During an outbreak, essentially everything in the environment can spread the bug due to the very high level of shedding by sick animals. “I want my producers to think of other scouring calves as the major source,” Groves says.
What’s most important to Groves is moving the heavy springers out of the calving pasture into a clean pasture. “Reducing the at-risk population is imperative to get an outbreak under control. We don’t want any more calves born into this highly contaminated environment.” In fact, it makes sense to always have your most at-risk population exposed to the least number of risk factors associated with the disease outbreak. “This is a lesson we learned as we adopted and implemented the principles of the Sandhills Calving System several years ago,” Groves says.
For the calves that are all ready affected, Groves suggests these actions:
Collect and submit diagnostic samples as soon as possible. “When you’re dealing with bugs like E.coli that change resistance patterns quickly, it’s very difficult to design effective antibiotic treatment protocols without the help of a good diagnostic lab.”
“In some severe outbreaks if we have some historical diagnostic susceptibility data available, we often elect to mass-treat every calf in the pasture that we consider at high risk, which are usually all the calves 2 weeks of age and younger.”
Adopt some management practices that minimize the amount of time calves spend concentrated around the herd; for example, unrolling bales of hay rather than using bale rings.
Minimize stress. “Sometimes if we try to move or sort the groups of cattle we are having problems with we over-stress them and compound problems,” Groves says.
Give calves supportive therapy such as IV and oral fluids and anti-inflammatories.
Give colostrum supplements for all calves under 24 hours of age.
Assess the effectiveness of treatment protocols and changes in management. “Usually we are effective in limiting the outbreak to one calving pasture,” Groves notes.
Act fast in an outbreak
When an outbreak of scours hits your client’s calves, it’s too late to talk about what he or she could have done to prevent it. Bob Larson, DVM, PhD, says the three immediate steps that should be taken to alleviate the situation are:
Treat and isolate affected calves.
Spread calves out; divide by age to help keep calves from grouping together.
Optimize the environment; put them on the best pasture available with good drainage, protection from wind and plenty of room.
For more information see:
R.L. Larson and J.W. Tyler. Reducing calf losses in beef herds. In: Frazer GS, ed. Veterinary Clinics of North America: Food Animal Practice Bovine Theriogenology. Vol 21(2). Philadelphia, PA: W.B. Saunders Company; 2005: 569-584.
R.L. Larson, J.W. Tyler, L.G. Schultz, R.K. Tessman, D.E. Hostetler. Management strategies to decrease calf death loss in beef herds. JAVMA 22:42-48, 2004.