News

Reducing the Need

By Heather Smith Thomas   |   Angus Journal
4/21/2017

Good health depends on many factors. Modern technology creating vaccines and antibiotics made disease prevention and treatment easier. For decades, cattle producers routinely used vaccination for prevention and antimicrobial drugs for treatment. Use of antimicrobials is being questioned today, however, due to drug-resistant pathogens. Resistance diminishes the effectiveness of some typically relied-upon drugs.

There’s also the issue of residues in food animals if drugs are used inappropriately or withdrawal times are not observed. Consumers are concerned about the safety of meat products. Beef producers and veterinarians are looking at alternatives to antimicrobials in dealing with disease. Key factors in this goal include reducing exposure to disease and keeping immunity strong. Several management tools can aid us in this effort.

Minimize exposure

Veterinarian Amelia Woolums, adjunct professor in large-animal medicine for the University of Georgia, says producers can often reduce the need for antibiotics with good management, decreasing disease challenges to the animal.

A major risk factor is commingling cattle from different sources.

“Purchased livestock should be kept separate from the herd for at least two weeks to make sure the new animals are not incubating a disease that might show up in a few days,” she says. “If you buy some heifers, don’t just put them out with your other heifers.” They might look healthy, but they could have been exposed to pathogens at the sale yard.

Another issue would be a disease like infectious bovine rhinotracheitis (IBR) that heifers may have encountered earlier in life and it shows up after they’ve been stressed.

“IBR is a herpes virus and can be latent, hiding in the body. A latent virus is just sitting there, but when the animal is stressed it can recrudesce (break out again after a dormant period). Then the animal will start shedding it again,” says Woolums.

“This is similar to people getting a cold sore — caused by another herpes virus that can remain dormant. When the person is healthy the virus remains latent, but when that person is stressed and tired, the virus recrudesces and a cold sore appears,” she explains.

The recommended period for quarantining new animals varies depending on the disease, but for most diseases two weeks would be enough for it to appear if the animal was incubating it. For some diseases, however, even a long quarantine is inadequate. Johne’s disease is an example, as is persistent infection (PI) with bovine viral diarrhea (BVD).

“Most diseases, like viruses that cause respiratory disease or GI (gastrointestinal) tract diseases that animals clear after they recover, shedding would probably occur in the two- to four-week period following stress,” says Woolums.

“Biosecurity includes isolation of new animals and minimal contact with other livestock,” she says. “If a neighbor doesn’t observe good biosecurity, it doesn’t do much good if you do, if cattle have fenceline contact or graze in community pastures.”

Cleanliness is also important in reducing risk. Pathogens that cause diarrhea, for instance, will be more problematic if many animals are crowded together, concentrating those pathogens and creating a challenge to the animals’ immune systems.

Andy Allen, veterinarian with Washington State University (WSU), works with the WSU Field Disease Investigation Unit. “We investigate disease outbreaks and increased incidence of disease within herds. One of the most common things associated with increased disease (and more use of antibiotics) is too many animals in too small an area.”

This is particularly problematic just before and during calving. Management of cows prior to calving is crucial for keeping the environment clean and preventing sickness in baby calves. Don’t calve in the same area where you fed cows through winter.

“If you leave cattle in the same area too long, there will be more bacteria, viruses and protozoa that cause calfhood diseases,” he points out. Calves are more vulnerable than cows because they don’t have an experienced immune system.

“There are ways to keep calving areas cleaner, such as the Sandhills Calving method. This involves moving pregnant cows to new calving grounds every seven to 10 days, leaving calved-out pairs behind in small groups according to age,” Allen explains.

The most vulnerable, those young calves, won’t have to contend with older calves that might be sick and shedding pathogens. The calving cows have clean ground that hasn’t already been contaminated by sick calves that shed pathogens in much higher numbers.

Building immunity

We now have vaccines against many common cattle diseases, but some vaccines have better proof of efficacy than others.

“Vaccines that are effective can be part of a good management program, providing a way to avoid the need for antibiotics,” says Woolums.

“Some producers don’t understand timing of vaccines, especially for calves during the first six to eight months of life. Boosters are important, especially for calves that may have maternal antibodies. You get a better effect with a booster, and those shots should be one or two months apart for maximum effect,” she explains.

“For calves, the foundation of good immunity is colostrum. The antibody molecules in colostrum can only be absorbed during the first few hours of life, however. We used to think a calf had 24 hours to obtain antibodies, but research shows absorption drops dramatically after 12 hours. Getting colostrum into the calf in the first two to four hours after birth is best,” says Woolums.

Giving the calf something to drink before it drinks colostrum can be counterproductive as it stimulates the gut to close faster. Then, when given colostrum, it may not be able to absorb the antibodies, says Woolums, citing an example at a dairy experiencing a high incidence of calf pneumonia.

“It was a big dairy, and it wasn’t convenient to get colostrum into the calf from its own mother or even from any cow,” she reports. “They were giving colostrum replacer first, then giving the good-quality colostrum later. The calves’ guts were closing after the replacer was fed, so they couldn’t benefit from the colostrum.”

Anything that impairs the calf’s ability to ingest and absorb maternal antibodies leaves it unprotected.

“Also, anything that makes a calf acidotic at birth can be a factor,” adds Woolums, explaining that after a difficult birth, a calf may lack oxygen and acids build up in the body due to decreased metabolism. The same happens if a calf is severely chilled.

“The acidotic calf may be unable to absorb antibodies from colostrum, even if you tube him with colostrum” she says. “[The] best thing to do in that situation is stimulate the calf’s breathing and get him warmed up. This should improve metabolism and help clear the acids. Then get colostrum into him immediately — maybe 10% to 20% more than you normally would. This might overcome that depressive effect.”

When passive transfer fails, calves may do okay if they aren’t challenged by infectious agents, she notes. “This is where cleanliness and biosecurity would be extremely important, with no room for error.”

Nutrition

Allen says the main thing a producer can do to optimize the immune system and minimize use of antibiotics is make sure cattle have good nutrition.

“This helps set up the immune system to be able to fight off infections. Diet needs to include adequate protein, energy, vitamins and trace minerals — with copper, selenium and zinc being the main ones we worry about in the Northwest,” he says. This may require testing feeds so a custom trace-mineral mix to fit a specific need can be developed.

“One mineral mix won’t fit every situation,” he adds.

You need to know what you are feeding.

“Just because hay is green doesn’t mean it has enough protein and energy,” Allen says. “You also don’t know the trace mineral levels.” Some soils are deficient in copper, and many areas are deficient in selenium, while others have too much selenium.

Sometimes other elements bind copper, making it unavailable to the body.

“Even if you provide the required amount of copper, it may not be enough if there is too much molybdenum, sulfur, iron or zinc that might bind to it. Understanding mineral relationships is important. Work with a nutritionist to determine proper levels of trace minerals for your ranch,” says Allen.

He continues, “Assessing body condition score (BCS) is crucial throughout the year, making sure your animals are in the ideal range of 5 or 6 (on a scale of 1 to 9). Producers try to find the most cost-effective way to feed cattle, but need to balance this with body condition.”

It might cost more in the long run if cattle become thin, causing higher incidence of disease and the need for more antibiotics.

“If calves have deficiencies of protein, energy, vitamins and minerals (especially vitamins A and E and trace minerals copper, zinc and selenium) for a prolonged period, they’ll have immune suppression,” says Woolums. “You can fix the immune suppression if you correct the deficit, but if calves get sick in the meantime, some of them might develop severe disease.”

If calves get pneumonia, they may end up with abscesses in their lungs, she says. This may impair their ability to grow, and they may never catch up.

A temporary deficiency, lasting only a few weeks, may have no serious effect,” Woolums says. “Nutrient deficiency doesn’t always cause problems with immune function, but if the deficiency is present for weeks to months it is more significant.”

While protein and energy are important, diets with more protein and energy may not provide extra benefit for the immune system, she notes. “The relationship between nutrition and immunity is complex. You don’t want deficiencies in important nutrients, but feeding excess won’t reliably help. Some studies showed that calves given more of a certain vitamin or mineral might have had a more rapid vaccine response, but these results are not consistent. Other studies have not shown this to be the case.”

The variable response, she says, may be partly the animals; some may have needed it and some didn’t.

“Adequate nutrition is important, but feeding excess — or feeding certain supplements — may not always improve immunity,” she says. “The important thing is to focus on making sure cattle have a good balanced diet without any deficiencies.”

Avoid excess stress

Stress hinders immune function. Reducing stress at weaning, during handling/working, shipping and severe weather, etc., may reduce incidence of disease. Avoid stacking too many stressors — such as weaning and shipping or weaning and working cattle in bad weather — at the same time.

However, a little stress is actually beneficial, according to Woolums.

“The body needs a little challenge to improve immune function,” she says. It’s similar to vaccination — a little antigen to stimulate the immune system into mounting a defense against future challenges. The animal that has no challenges, no stress and no prior experience with a certain pathogen has no defenses.

“A recent study at Iowa State University looked at calves vaccinated at weaning. We generally avoid vaccinating calves the same time you wean because that’s a time of stress, and they won’t mount a good immune response,” Woolums says. “In this situation the calves were on the farm of origin and not moved. They were weaned and vaccinated, but nothing else happened to them. They’d already been castrated and dehorned. They stayed with their peer group and weren’t exposed to a new environment or different cattle.”

The researchers were looking at things that affect antibody response of calves, specifically BVD type II antibody response to vaccination.

“They compared two groups for this study. They vaccinated one group three weeks before weaning and another group when they were weaned. The group vaccinated at the time of weaning actually had a little better immune response to the vaccine than the calves that were vaccinated before they were weaned,” she says.

“This is the opposite of what we’d expect. I think the reason this worked was that the calves did not have any other stressors at weaning. The other thing is that antibodies from the mother (passive transfer from colostrum) can sometimes block response to vaccination. Calves can respond to vaccination when they have maternal antibodies, but the higher the level of maternal antibodies, the more likely those will block the vaccine.”

The older the calf, the less likely there is a chance of interference from maternal antibodies.

“The calves vaccinated at weaning were three weeks older than those vaccinated ahead of weaning. In three weeks the maternal antibodies have dropped a little more,” she says.

This can make a difference, depending on how young the calves are at weaning, whether you wean at 9 months, 6 months or younger. The thing to realize is that not all stress is bad, she says. A short-term stress or just one kind of stress may actually improve immune response. Multiple stressors at once or stress that goes on for a long time is what generally suppresses the immune system.

Allen says there are various ways to reduce stress at weaning, such as fenceline weaning, nose flaps, etc.

It also helps to train calves to eat out of bunks and to drink from water troughs before weaning or before shipping, so they won’t be in an unfamiliar situation when they go to a feedlot, he says.

Make sure working facilities flow well. The less time cattle have to be confined, and the quieter they are moved and handled, the less stressed they will be.

“During stress their cortisol levels go up, and when that happens their immune system drops,” says Allen. “If we can keep stresses to a minimum, even practicing with a group of calves, putting them quietly through the facility without being worked, they are not as upset and stressed when you put them through again.”

Cows that don’t get upset when handled do better. They can be trained to tolerate being worked and handled if you keep stress levels low. “There are always ways to improve cattle handling to keep it less stressful,” he says.

Editor’s Note: Heather Smith Thomas is a freelance writer and cattlewoman from Salmon, Idaho.