The use of pathogen-killing drugs is questioned today due to increasing numbers of drug-resistant pathogens.
There is also the issue of drug residues in food animals if drugs are used inappropriately or withdrawal times are not observed.
Beef producers and veterinarians are looking at alternatives to antimicrobial use in dealing with disease.
Reduce exposure
Dr. Amelia Woolums, professor of large-animal medicine at the University of Georgia, says we can often reduce the need for antibiotics, using good management to decrease the chances of cattle being exposed to disease.
A major risk factor is commingling cattle from different sources. “When you buy livestock, they should not immediately be turned out with the herd.
They should be kept in a separate place on the farm for at least two weeks. They might look healthy the day you buy them, but may be incubating a disease that would show up in a few days,” she says.
Also, a disease, like IBR, that cattle may have encountered earlier in life may show up again after they’ve been stressed.
“IBR is a herpes virus. It can be latent, hiding in the body and not multiplying or being shed.
"But when the animal is stressed, it can recrudesce. Then the animal starts shedding it again,” says Woolums.
“This is similar to people getting a cold sore – caused by another herpes virus that can remain dormant in the body.
"When the person is healthy, the virus remains latent. But when that person is stressed, the virus recrudesces, and the cold sore appears.”
Cleanliness is another important factor in reducing chance for disease. “The agents that cause diarrhea, for instance, will be more of a problem if you have animals crowded together, concentrating those pathogens,” she says.
Vaccination
We have effective vaccines against some common cattle diseases. “These vaccines provide another way to avoid the need for antibiotics and can be an important part of a good management program,” says Woolums.
“Calves are most likely to benefit from two doses of a vaccine. Boosters are important, especially for calves that may have maternal antibodies,” she explains.
Immunity
“For newborns, the foundation of good immunity is getting enough colostrum,” says Woolums. “Antibody molecules in colostrum can only be absorbed during the first few hours.
"If the calf drinks something else first, this stimulates the gut to close faster. Then it can’t absorb colostrum, even if a calf gets colostrum later,” she says.
“We were working with a big dairy that had problems with calf pneumonia and found the calves had inadequate passive transfer of antibodies.
Calves were being given a colostrum replacer first, and good-quality colostrum later. The calves’ guts were closing after the replacer was fed; they couldn’t benefit from the good colostrum.”
Anything that impairs a calf’s ability to ingest and absorb maternal antibodies will leave him unprotected – such as the cow not mothering the calf, teats too big or the calf becoming chilled before he can get up and nurse.
“Anything that makes a calf acidotic at birth (such as dystocia) can be a factor. If the calf didn’t get enough oxygen, acids build up in the body; decreased metabolism leads to generation of acids.
The acidotic calf may not be able to absorb the antibodies from colostrum, even if you tube him with colostrum,” she says.
"For a healthy immune system the first thing is colostrum, along with proper nutrition.
“If calves have deficiencies of protein, energy, vitamins and minerals (especially vitamins A and E and the trace minerals copper, zinc and selenium) for a prolonged period of time they suffer immune suppression,” Woolums says.
Avoid excessive stress
Stress hinders immune function. Reducing stress in cattle (at weaning, during handling or working, shipping or severe weather) may reduce incidence of disease.
The important thing is to not stack too many stressors at once – such as weaning and shipping at the same time.
“A short-term stress or just one kind of stress may not be harmful. Multiple stressors at one time or a stress that goes on for a long time is what generally suppresses the immune system,” says Woolums.
Immune stimulants
There are supplements and injectable products aimed at improving or stimulating the immune system.
“Immune stimulants can be given at times of stress – when the immune system is under attack, such as at weaning – and may be helpful, but we need more research on how reliable they are,” says Woolums.
“It may depend on when the stimulants were given, when the stress occurred, etc.”
There are several kinds of immune stimulants, and they work in different ways. “Some cause inflammation; they are made of bacterial components and induce a response similar to an early bacterial infection.
This kick-starts the immune system and stimulates a reaction. It’s like giving the animal a mild infection – to trigger the immune system into action if it isn’t doing its job,” she says.
“Ask the company that sells the product to show data to support their claims. Some products are better supported with research than others,” Woolums says.
Probiotics and prebiotics
Kyle Newman, Ph.D., microbiologist and lab director at Venture Laboratories in Kentucky, explains that in the absence of antibiotics, we do what we can to boost the immune system.
This includes recognizing beneficial effects of “good” bugs in the body and use of probiotics and prebiotics in animal health.
Microbes in the rumen enable cattle to process and utilize forages. It is essential that the microbial population be healthy and in appropriate numbers or balance for proper digestion and health of the animal.
Newman explains that the GI tract not only digests food but is the largest, most complex immune organ in the body.
“Any other place in the immune system, if there is a foreign invader, it is attacked and killed.
"The GI tract, by contrast, has to sort through all the material and differentiate ‘good guy’ from ‘bad guy’ and decide when to attack,” he explains.
“Because of the extremely diverse microbial population in the GI tract, bacteria in the tract far outnumber the body cells that make up that animal.
"Feeding the bacterial cells and making sure they are good ones makes sense,” says Newman.
There are several types of GI-tract supplements, including yeasts, probiotics and prebiotics. Probiotics help maintain a healthy gut balance.
Yeast cultures indirectly improve fiber digestion. Probiotics include bacterial and yeast cultures, whereas prebiotics are non-digestible sugars that play a beneficial role in aiding the “good” microbes and protecting against the “bad” ones.
“In a world where antibiotics are less effective, the most you can do for an animal is improve its own immunity.
"One way is by competitive exclusion – crowding out the bad guys by feeding good guys. Probiotics shift the balance by flooding the system with good guys.
"Prebiotics feed the good guys or pull out the bad guys,” says Newman.
Probiotics and prebiotics re-establish gut health when something stresses the animal and alters microbial populations.
“If antibiotic therapy has killed both the bad guys and the good guys, you must re-establish the good guys. If stress shifts the microbe population, you can overcome that situation,” he says.
“With some prebiotics, you are feeding the good microbes already present in the gut,” explains Newman. “Another prebiotic is mannan oligosaccharide (MOS).
This one improves overall immune function – and beneficially alters immunoglobulin and circulating antibody levels.
MOS products provide a binding site that the bad ones stick to, like flies on fly-paper, and take them on through the intestinal tract.”
Research has shown that MOS can boost the immune system, both cellular and humoral. “You can boost the immunoglobulins in colostrum by supplementing the dam with MOS prior to calving,” Newman explains.
“I call colostrum the ‘get-out-of-jail-free’ cards. The newborn has to suckle anyway, so the more good stuff you can have in colostrum, the better off the animal will be – as long as the newborn nurses before gut closure and before pathogens are introduced into the GI tract.”
“We did a trial here 10 years ago. It showed that if you fed MOS to the cow, her immune status and immunoglobulins in colostrum were greater for the calf and created better antibody titers for what you vaccinated the cow for before calving,” says Newman.
Research on Bio-Mos (the only MOS product that’s been tested on its effects on vaccination) has shown an increase in vaccination titers with certain vaccines in a number of animal species.
Lactobacillus is a popular probiotic for cattle, especially in newborn calves to help establish proper gut microflora. “Lactobacillus and other micro-organisms help exclude (competitively or otherwise) harmful microbes.
Mindy Brashears (now at Texas Tech) did a trial with lactobacillus microbials in combating E. coli 0157:H7 and showed these to be helpful.
Lactobacillus is also being used in mature ruminants. Dr. Brashears showed it helped exclude E. coli 0157:H7 in feedlot cattle before they went for slaughter, and also seemed to help with acidosis conditions,” says Newman. 
Heather Smith Thomas is a freelance writer based in Idaho.
PHOTO
Antibody molecules in colostrum can only be absorbed during the first few hours of a calf’s life, so it’s critical to have calves suck from the dam quickly. Photo by Heather Thomas.
Transfer factor
Dr. Steve Slagle (veterinarian in La Grande, Oregon) has been using a transfer factor product since 1999.
“This natural immune enhancer derives efficacy from a protein produced by the immune system’s T lymphocytes. The protein is called transfer factor and is also found in colostrum.
"To create human and animal products, this protein is extracted from cow colostrum,” he explains.
The body’s immune system produces memory molecules whenever it is exposed to disease or receives a vaccination.
These molecules are bioactive peptides called transfer factors and are passed from the cow to the calf via colostrum. This transfer helps educate the calf’s immune response cells.
In the early 1900s, doctors noticed immunities could be transferred from one person to another by blood transfusions.
Then in 1949, Dr. H. Sherwood Lawrence, a researcher working on tuberculosis in humans, found he could transfer immunity to his patients by using dialyzed leukocytes.
When this extract was from a blood donor who was resistant to the pathogen and injected into a patient who had no immunity, the immunity of the donor was transferred to the naïve patient. Part of the white blood cell contained what Lawrence dubbed “transfer factor.”
Research was slow, however, because more exciting discoveries revolved around antimicrobials.
There were very few studies on transfer factor until the late 1980s, when researchers found that bovine colostrum contains significant amounts of this ingredient that stimulates both humoral and cellular immunity.
Veterinary researchers discovered that transfer factor is one of the protein messengers released by antigen-sensitized white blood cells.
A veterinary product was created for cattle during stress periods to help prevent illness. “If we give it to newborn calves, it’s the equivalent of giving them 6 to 8 gallons of colostrum in terms of the protective factors,” says Slagle.
“At weaning, they are often 5 to 10 percent heavier than similar calves that did not receive the product – depending on how stressed the animals are during early weeks of life,” he says. Some producers use the product to help prevent scours in baby calves.
If calves receive the product at weaning they typically gain an extra half-pound to 1 pound per day during preconditioning or when they go to a feedlot.
“With use of this product, death loss is often reduced to near zero because the ones that do get sick don’t get that sick. Usually one treatment and they turn around,” says Slagle.
“We did our first feedlot study at the veterinary school in Missouri with 240 head of 440-pound to 450-pound calves that were taken off wheat grass and transported 40 miles to the feedlot.
"Our study compared transfer factor with Micotil when Micotil first came out. We treated 80 calves with our product, 80 with the new antibiotic and 80 with nothing.
"They’d all been vaccinated and dewormed when entering the feedlot. The group that received our product had no illness, the Micotil group had 12 treats, and the control group had 17 treats.
"Ours gained over three-quarters of pound per day more than the Micotil group,” says Slagle.
“Transfer factors are like an instant temporary vaccine. The protein attaches to the T-lymphocytes, which are the master immune cells that recognize pathogens.
"When they take in this protein, it’s like an identification molecule. It will recognize salmonella, for instance, and tell the immune system there’s a problem that needs to be taken care of.
The immune system targets that pathogen and sets in motion an immune response to destroy it,” he explains.
