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Can feed additives play a role in addressing calf health and performance challenges?

Paige N. Gott for Progressive Dairy Published on 02 December 2020

Replacement heifers are critical to the longevity and sustainability of dairy operations. Special attention should be paid to raising calves, as many aspects influence lifelong health and future productivity, including maternal factors during gestation, colostrum management, nutrition, vaccination program, housing and environmental conditions.

Implementation of preventive strategies is favored over treating animals once sick; however, when disease does occur, treatment is justified whether it is supportive therapy through use of electrolytes or fluids or judicious use of antimicrobials under veterinary oversight. Feed additives can be part of the nutritional approach to reduce disease challenges by improving animal resilience, leading to better health, growth and performance in calves, which in turn leads to a healthier and more productive milking herd.

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What are feed additives?

Feed additives are ingredients typically fed in small quantities that do not necessarily provide a direct supply of required nutrients but have other benefits. Many categories of feed additives exist, but some used in calf diets include probiotics, prebiotics, phytogenic feed additives and mycotoxin mitigation products. Additionally, medicated feed additives including antimicrobials, ionophores and antiparasitics can be used, but many of these options require veterinary oversight. Feed additives can be supplemented in liquid diets through manufacturing into calf milk replacer powder or by adding directly on-farm to reconstituted milk replacer or non-saleable milk fed to calves. They can also be incorporated into solid feeds, such as starters and grower rations.

Before we dig into the details of additives and how they might help limit disease, let’s look at some of the potential health challenges calves experience.

Major causes of illness and death in US dairy calves

According to the National Animal Health Monitoring System (NAHMS) Dairy 2014 study, approximately one-third of pre-weaned calves experience some sort of illness (morbidity). Of the calves reported ill, digestive upsets such as scours were the primary cause of illness (50.9%), with respiratory illness (pneumonia) reported in 28.1% of ill calves. Concurrent disease with digestive and respiratory signs accounted for 5.4% of illnesses, and 23.6% of calves had other causes of illness, such as fever, navel infections, injuries or lameness.

Based on the NAHMS Dairy 2014 study, 5% of calves die (mortality) prior to weaning. Thirty-two percent of those deaths were attributed to digestive upsets. Death due to scours is often a result of dehydration and/or septicemia (pathogen and/or toxins in the blood). Respiratory disease was associated with 14.1% of deaths, while 7% of calf deaths were caused by simultaneous digestive and respiratory disease. Another 38.3% of deaths were attributed to either unknown or other causes. Limited information is available for weaned heifers, but the NAHMS Dairy 2002 study reported nearly 2% of heifers die between weaning and calving, with over half of those deaths caused by respiratory disease (50.4%).

 120220 gott table 1

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120220 gott table 2

Common pathogenic causes of scour are listed in Table 1, while pathogens associated with pneumonia are listed in Table 2. Many pathogens exist naturally in the environment, so calves are likely exposed, but not all calves develop disease. Ill calves, as well as those calves with subclinical infections, can shed and transfer pathogens to others, spreading disease. Additional factors beyond pathogens themselves contribute to development of disease, including:

  • Difficult calving, weak calves
  • Poor calving pen sanitation
  • Failure of passive transfer or inadequate immune system development due to poor colostrum management
  • Inadequate calf nutrition
  • Erratic feeding schedule and feed preparation (including incorrect temperature or mixing)
  • Compromised feed hygiene leading to high pathogen loads
  • Inadequate vaccination and parasite control
  • Mycotoxins in feeds
  • Cold, wet weather or poor air quality in confined housing
  • Stressors related to weaning, commingling, transportation or overcrowding
  • Poor biosecurity

Where can feed additives fit?

In addition to good colostrum management, proper hygiene, biosecurity, utilization of vaccination and parasite control programs developed under veterinary guidance, and monitoring calves to allow early identification of illness and appropriate intervention, feed additives can contribute to a herd’s disease prevention strategy by helping reduce health challenges. These specialty ingredients add value to the diet by providing benefits that can lead to better health, and in return, improve productivity and longevity. Many categories of feed additives are available on the market, and within those categories an even greater number of products can be found. A few common categories and how they can promote healthy, productive calves are:

1. Probiotics are live, naturally occurring microorganisms, including – predominantly – bacteria (such as species of lactobacillus, bifidobacterium and bacillus) or yeast (like Saccharomyces cerevisiae) that are often referred to as “direct-fed microbials.” These microorganisms can influence the gastrointestinal (GI) tract environment by helping establish beneficial gut microbiota and enhancing intestinal integrity, which may improve resistance to diseases like scours and promote overall digestive health.

2. Prebiotics, on the other hand, are not alive but rather are indigestible carbohydrates that provide nutrients to selectively stimulate beneficial gut microorganisms. These compounds mostly include yeast cell wall components (mannan-oligosaccharides [MOS] and beta-glucans), nucleotides, fructans and galactans. Stimulating commensal microbiota helps limit opportunistic pathogens from proliferating and colonizing the intestines. Some products also directly combat disease by binding Gram-negative bacterial pathogens, such as E. coli and salmonella, which are often linked to scours.

3. Phytogenic feed additives (PFAs) are substances of plant origin, which are also referred to as “botanicals” or “phytochemicals.” Essential oils are one class of phytogenic ingredient, while other categories include non-volatile phytochemical compounds from herbs and spices. Some familiar phytogenic ingredients include oregano, cinnamon, vanilla and peppermint oil. Many products are available on the market, and composition can vary tremendously, ranging from basic (consisting of one ingredient, like oregano oil) to very complex (comprised of a blend of multiple ingredients). These products can increase intake by promoting palatability through providing favorable flavors and aromas (or masking unpleasant ones). PFAs have additional biological effects beyond their sensory aspects, such as anti-inflammatory and antioxidative activities to support gut integrity and mucosal layers, and/or antimicrobial properties to reduce pathogen challenge, as well as other features, such as stimulating digestive secretions that support digestibility, promote a healthy intestinal epithelium and protect the gut. All of these aspects can help improve gut health and functionality, which can lead to improved performance.

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4. Mycotoxin mitigation products (often referred to as “binders”) are a commonly used strategy in mature cow diets, but these products can also have benefits in calf feeds. Mycotoxins are secondary metabolites produced by molds, which can contaminate a wide variety of feedstuffs, including grains and forages. These toxins are detrimental to animal health and productivity, as they cause a variety of negative effects, including reduced feed intake, diarrhea, immune dysfunction and hormonal imbalances that interrupt normal reproductive processes. Calves are especially susceptible to the negative effects of mycotoxins. Hundreds of mycotoxins are known to exist, including aflatoxins, deoxynivalenol (aka “vomitoxin”), fumonisins and zearalenone. Mycotoxins have diverse structures and therefore target different tissues and organs in the body, leading to diverse consequences. Mycotoxins can predispose calves to diseases, such as scours or pneumonia, by compromising gut integrity and immune function, leaving animals more susceptible to pathogens. Due to variation in the physical and chemical properties of mycotoxins, not all can be adequately controlled through binding. Additional modes of action – including biotransformation, which degrades or alters the target mycotoxin, greatly reducing toxicity or preventing its action in the animal – are required for broad spectrum protection. Furthermore, additional benefits to immune function, liver health and gut integrity can be provided through use of certain phytogenic ingredients.

5. Medicated feed additives – such as Ionophores, anticoccidials and antiparasitic feed additives, as well as antimicrobials – are available. Veterinary oversight is required for use of many of these products, so consult your veterinarian for guidance and proper documentation to utilize these feed additives. There is rising concern about overuse of pharmaceuticals leading to loss of efficacy and resistant pathogens. Implementation of proper management practices in combination with non-medicated alternatives can help reduce antimicrobial use.

There are many feed additives on the market that may be beneficial to calf health, but the use of these products will never preclude the need for good hygiene, proper nutrition and efforts to limit other stresses coming from the environment and management practices. However, feed additives are useful tools that can help support health and productivity in calves, as well as the rest of the herd.   end mark

PHOTO: In addition to good colostrum management, proper hygiene, biosecurity, utilization of vaccination and parasite control programs, and monitoring calves for illness identification and appropriate intervention, feed additives can contribute to a herd’s disease prevention strategy by helping reduce health challenges. Photo courtesy of Biomin America Inc.

Paige N. Gott
  • Paige N. Gott

  • Senior Ruminant Technical Manager – Dairy
  • Biomin America Inc.
  • Email Paige N. Gott

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