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The good, the bad and the ugly: What you need to know about gut health

Progressive Dairyman Field Editor Jenna Hurty-Person Published on 24 September 2018

Calf diarrhea is a costly, but common problem on today’s dairies. In fact, according to the 2014 NAHMS data, diarrhea was responsible for 56 percent of pre-weaned heifer deaths. In addition, recent research shows that even when calves overcome this disease challenge, there are still negative consequences in the form of reduced first-lactation milk production and increased age at first calving. Thus, preventing diarrhea is essential to raising healthy calves.

During her presentation at the 2018 Vita Plus Dairy Calf Summit, Jenn Rowntree, a calf and heifer specialist at Vita Plus, shared her insight into this topic and why a healthy gut is essential to raising a healthy calf.

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The mucosal immune system

The mucosal immune system lines the entire GI tract and serves as a line of defense against invading bacteria. Intrinsic to this, Rowntree said, is the calf’s gut microbiome, which consists of good bacteria in the GI tract. This microbiome is essential to the calf’s health as it plays a critical role in the calf’s metabolism, GI tract regulation and immune response by detecting, preventing and eliminating bad bacteria from the GI tract. 

In addition to the bacteria, the mucosal immune system possesses physical and chemical barriers that protect the calf from pathogens. The physical barriers consist of the mucus layer, which traps microbiota, and the epithelium, which contains the tight junctions. These tight junctions act as the primary regulator of intestinal barrier function. The chemical barriers serve to limit the growth of bad bacteria while protecting the good bacteria in the mucosa layer. In addition, the antimicrobial peptides that act as part of the chemical barrier help to identify and kill pathogens.

Unfortunately, this important component of the calf’s immune system is not impervious and can be damaged by stress, antibiotics and invasive and opportunistic pathogens, such as Clostridium perfringens, Cryptosporidium parvum, coccidia and rotavirus and coronavirus.

Producers are often advised to limit calf stress. One major reason for this is the impact stress has on gut health. When an animal is stressed, it releases hormones that cause the gut environment to shift, making it easier for bad bacteria to take over and overwhelm the calf’s immune system, causing it to become ill.

Antibiotics are not necessarily the answer either and should only be used when necessary, Rowntree said, since they target good bacteria as well as bad. In fact, in some cases, antibiotics can actually make it easier for bacteria to take over since the good bacteria have been diminished, causing a microbial imbalance. With this in mind, Rowntree suggested calves with diarrhea and a normal appetite, but no fever, be monitored closely and given electrolytes, while calves that have diarrhea, no appetite and a fever be given a broad-spectrum antibiotic and electrolytes. Rowntree did note that this should always be done under vet supervision and guidance as situations will vary.

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To give calves the best chance at staying healthy, Rowntree said producers need to do three things:

  1. Promote a diverse gut microbiome through a robust mucosal immune system and good nutrition.
  2. Limit stress.
  3. Reduce exposure to pathogens through proper biosecurity protocols.

Focus on nutrition

At birth, the calf’s microbiome is almost or completely nonexistent, but that changes drastically in the first 24 hours. This change is important because the sooner these good bacteria can establish themselves, the harder it is for bad bacteria to establish themselves in the gut. Because of this, Rowntree advised producers to feed calves at least 4 quarts of high-quality, clean colostrum within four hours of birth. The glucose in the colostrum acts as a natural prebiotic and feeds the good bacteria. This helps them become established more quickly, protecting the calf.

To further assist with calf gut health development, Rowntree said she has seen farms have good success with feeding small amounts of colostrum for the first two weeks of life in addition to the initial 4-quart colostrum feeding at birth. She suggested doing this by freezing colostrum in ice cube trays and adding one colostrum cube per calf per feeding.

Next, producers need to focus on milk quality and quantity. Milk should be clean and free of harmful bacteria, have a similar osmolality to cow’s milk and be fed at a rate of 12 to 14 percent solids. In addition, Rowntree said producers need to make sure to feed calves enough milk to not only meet their energy requirements for growth, but it also needs to support the calf’s immune function even during temperature extremes.

Rowntree also advised producers to provide calves with high-quality calf starter as soon as possible. Doing so not only promotes rumen development and facilitates early weaning, it also increases the calf’s ability to fight disease. It does this by encouraging an earlier expression of antimicrobial defense molecules, which help identify and kill pathogens, and it positively impacts the GI tract barrier function and immune responses.

Finally, feeding probiotics can greatly assist in the calf’s gut health and development as these are a source of live, viable beneficial bacteria or yeast that interact with the gut’s microflora, epithelium and immune cells. The one caution Rowntree had here, however, is that producers need to know where the probiotics are coming from and they need to be getting to the calf in a live form for maximum benefit. Probiotics, she said, can still be beneficial to the calf when they’re dead, but that is not always the case. 

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Limit calf stress

As was already mentioned, stress can have a detrimental impact on the environment in the GI tract and in turn calf health. To mitigate this, producers should focus on these seven areas:

  • Minimize pain associated with procedures whenever possible
  • Avoid simultaneous stressors – dehorning, vaccines, moves
  • Gradual weaning
  • Temperature control – avoid heat or cold stress (40ºF to 70ºF is ideal)
  • Dry, well-bedded environment
  • Adequate ventilation, volume and area per calf
  • Fly control

Minimize pathogen exposure

Rowntree said she likes to think of pathogen exposure like a balancing act. On one side of the scale is the calf’s immune system, and on the other is pathogen exposure. The goal of the farm should be to keep this balance always tipped in the calf’s favor through proper biosecurity and biocontainment practices, by mitigating the calf’s opportunities for pathogen exposure and by providing the calf with the necessary tools to fight off disease exposure when it does occur.

The reality is diarrhea and the pathogens that cause it will always have some presence on a dairy farm. However, with the proper tools and management, producers can reduce its prevalence on their farm and give the calves that do become ill the tools they need to overcome that disease challenge.  end mark

This article originally ran in the Vita Plus July 2, 2018, Starting Strong enewsletter.

Jenna Hurty-Person
  • Jenna Hurty-Person

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