The invisible war
Calf illness often starts out invisible. By the time it’s noticed, the calf is significantly ill – requiring more man hours and medication – and it often dies.
In a presentation by the Dairy Calf & Heifer Association, Dr. Leonardo Bringhenti, DVM, Ph.D., AHV International, discussed the ongoing challenges of respiratory disease in calves and provided some new information on potential solutions.
Bringhenti stated that the average short-term cost for BRD is about $42.15, which covers initial and short-term treatment for one calf. Studies between 1978 and 2020 followed calves with BRD and showed lower average daily gain, higher chances of dying, higher odds of herd removal before first calving and lower milk production in first lactation.
Neonatal diarrhea is another problem. Calves with history of diarrhea during the preweaning period had lower probability of becoming pregnant as heifers. They also had reduced milk and lower ADG.
Bringhenti followed 217 newborn Holstein calves to determine pneumonia and ear infections. He collected data on the upper respiratory tracts of animals and analyzed interactions between the immune system and pathogens to determine factors that influence calves during the preweaning period.
“The first thing that happens to calves before disease is infection,” said Bringhenti. “Infection is when pathogens enter the respiratory tract, start to colonize and live there without asking. The second thing that happens to calves is inflammation. That happens seven days after we see the initial infections. The third thing is disease, which occurs most commonly at around 20 days of age.”
Bringhenti believes biofilm has a role in infection and subsequent disease. Biofilm is a cluster of bacteria attached to a surface or attached to other bacteria. This builds a wall of bacteria that protects microorganisms. The biofilm matrix contains polysaccharides, proteins and DNA.
In a more familiar sense, biofilm is commonly recognized in the environment. It adheres to surfaces in a protective matrix of slime. Biofilm can form on surfaces including glass, plastic and stainless steel. Although most biofilm exists outside the calf, Bringhenti referenced biofilm that occurs inside the calf but acts in much the same way.
“It’s a lot of bacteria getting together and forming a wall,” said Bringhenti. “When one bacterium is alone, it is more likely to be killed, but when bacteria form a wall, the immune system is unable to penetrate. It’s a mechanism of defense of bacteria against threats such as antibiotics and the immune system.”
Biofilm inside the calf is an adaptation for metabolic changes of bacteria “waiting” to cause a threat. The immune system and antibiotics are not efficient in penetrating biofilm, which keeps the bacteria inside the animal longer, leading to chronic problems.
Bringhenti explained the concept of “quorum sensing” in which molecules inside the biofilm communicate among bacteria. “They release molecules and can communicate,” he said. “If there is a threat and an antibiotic or a lot of immune cells are in the environment of the upper respiratory tract, they start ‘talking’ to each other. More bacteria start getting together and create a biofi lm. The bacteria that were by themselves change to a biofilm formation. Now the bacteria are protected from the immune system or antibiotics.”
Biofilm plays an important role in respiratory disease in calves and makes it difficult to treat certain infections. Bacteria protected by biofilm are more resistant to treatment, resulting in chronic infections.
The solution might be preventing the formation of biofilm inside animals.
“There is technology called ‘quorum quenching,’” said Bringhenti. “This disrupts communication between bacteria and avoids the formation of biofilm. If the biofilm is already formed, we can break down the biofilm inside the animal. That way we aren’t killing the bacteria directly – we are making them susceptible to be killed because they are no longer in a biofilm formation. Then we can clear the infection more easily.”
Bacteria can remain in animals for a long time. In many cases, the animal seems to have improved and the farmer believes the respiratory problem has been solved. However, infection shows up again because the bacteria is out of the biofilm and begins to reproduce.
Biofilm-associated bacteria exhibit increased resistance to antimicrobial agents, and biofilms may contribute to development of chronic BRD.
To fight BRD and other early life illnesses in calves, Bringhenti advised dairy farmers to begin with the initial, simple measures such as ensuring a clean, dry environment, proper colostrum management, avoiding stressing calves and maintaining solid SOPs for raising calves.
“Everything needs to be running perfectly in order to have healthier calves,” he said, “then maybe the early life problems wouldn’t be happening.”
When animals with BRD are treated multiple times, it likely means the microorganisms inside the calves are already resistant and biofilm is probably playing a role in keeping BRD chronic.
However, illness still occurs on well-managed farms. In a study of quorum quenching, the objective was to evaluate herbal blend products on the health and performance of pre-weaned dairy and beef on dairy calves.
“Herbal blend products disrupt biofilm,” said Bringhenti. Calf Start and Respi products were tested. “They have quorum quenching technology and other nutrients.”
These thiosulfinate compounds are herbal extracts, usually extracts from the Allium family (garlic and onion).
Considering the preweaning period of 56 days, calves in trials remained in hutches for several more days and were monitored for BRD and scours. Calves that received the supplements had higher ADGs.
While trials have not proven that thiosulfinate supplements are effective at battling BRD, there is no proof they are ineffective. Further research should reveal whether such supplements are effective.
by Sally Colby
