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A novel look at feed additives for beef cattle

Aimee Hafla for Progressive Cattle Published on 24 December 2019

Increasing consumer pressure to reduce or eliminate the use of antibiotics continues to motivate livestock producers to evaluate novel feed additives that offer health and production benefits but do not require veterinary oversight.

However, sorting through the growing selection of products and ingredients can leave even a well-versed nutritionist confused. The following discussion is not a comprehensive list of all currently available feed additives, but is instead a brief description of some available technologies and the potential benefits they offer.

Ionophores are possibly the most commonly used feed additive in the beef cattle industry, with 90.5% of feedlots with 1,000-plus animals using an ionophore.

Ionophores are classified as an antibiotic by the FDA, and their primary mode of action is to disrupt the movement of ions across the membranes of certain bacteria found in the rumen. This results in a shift toward the type of bacterial populations that produce propionate, which is the most favorable volatile fatty acid in relation to animal performance.

Additionally, ionophores prevent and control the occurrence of coccidiosis, which can be particularly problematic for young cattle. A combined analysis containing the results of 169 feedlot trials found that the use of monensin sodium improved feed conversion of feedlot cattle by 6.4% (through decreased dry matter consumption of 3.1% and improved average daily gain of 2.5%). Even though ionophores are classified as antibiotics, they are not considered medically important to humans and therefore can be purchased and used with no veterinary oversight.

Probiotics (direct-fed microbials) are live and viable, naturally occurring microorganisms that provide a health benefit to the host that consumes them, and primarily include bacteria and yeasts, or a mix of these organisms. Active live yeasts have shown promise in dairy cattle diets, resulting in increased milk production and dry matter intake.

Research conducted with feedlot cattle indicates that live yeast improves diet digestibility and may stabilize rumen pH by mitigating excessive lactic acid production; ideally this will result in improved nutrient utilization. Several studies have documented health benefits of feeding yeast in receiving cattle, which include a reduction in cattle pulled for repeat treatments and an increase in appetite. Current research is focusing on the potential use of yeast products to reduce the occurrence of liver abscesses in feedlot cattle.

The use of bacteria-based probiotics in beef cattle began as a pre-harvest food safety measure, by reducing fecal shedding of pathogens, such as E. coli. Typically, bacteria are discussed as either “lactic acid producing” or “lactic acid utilizing,” with some falling into “other categories.” Bacteria that produce lactic acid in the rumen may help mitigate low rumen pH by facilitating the growth of the bacteria that use lactic acid. Lactic acid- utilizing bacteria help prevent the accumulation of lactic acid.

Furthermore, the physical presence or “peppering” of beneficial bacteria on the walls of the lower gut may prevent the attachment and growth of pathogens. Additional research on various strains of probiotic bacteria have also focused on stimulating the immune system, with the intent of reducing the occurrence and impact of respiratory illness; however, impacts on health and performance have been variable. Both yeast and bacterial cells require continuous supply (daily) in the feedstuffs to reach beneficial concentrations and persist in the rumen.

Prebiotics are nondigestible substrates that provide nutrition to the beneficial gut bacteria or protect against pathogenic organisms. Yeast culture components, which include yeast cell wall parts, have a different mode of action compared to active live yeast. Mannan and fructo-oligosaccharides, found in yeast fractions, attract and bind pathogens so they can be flushed from the digestive tract without causing disease. These compounds, sometimes referred to as “refined functional carbohydrates,” can be very effective at binding gram-negative bacteria, such as salmonella and E. coli.

Often, yeast culture components will be combined with whole live yeast in one product, and those types of products make up a significant proportion of the research trials evaluating “direct-fed microbials.” It is likely that the effectiveness of yeast-based direct-fed microbials originate from both the yeast organism and the prebiotic component.

Enzymes are specialized proteins that speed up chemical reactions, such as breaking down organic compounds in feed into substances which are more readily usable by the animal or microbes. Different enzymes work on specific substrates; for example, amylolytic enzymes degrade starches and fibrolytic enzymes degrade fiber.

The purpose of supplementing enzymes to ruminant livestock is to enhance the digestibility of feedstuffs. The digestibility of forage cell walls can limit nutrient uptake, especially if rumen conditions are not optimal for fiber digestion. Starch availability in corn is significantly impacted by processing, moisture and prolamine content but can be enhanced by supplementation with a starch-digesting enzyme. Responses to enzyme supplementation in beef cattle consuming high-grain diets can vary, depending on the activity of the enzyme and baseline digestibility of the diet. Evaluation of diet digestibility and individual ingredients is necessary when considering the use of a feed enzyme product.

Essential oils are bioactive metabolites produced by plants as a means of defense, rather than for growth or reproduction. Some common essential oils include cinnamaldehyde (cinnamon extract) and capsicum annuum (hot pepper extract). Various essential oils have been found to alter rumen microbial populations, impact rumen fermentation and to have broad antimicrobial properties when evaluated with in vitro (test tube) trials. Specifically, essential oils appear to have similar ruminal effects as ionophores, shifting fermentation toward propionate and decreasing ammonia concentration and methane production.

However, evidence supporting the use of essential oils in feedlot cattle raised in commercial production systems is limited, and research documenting improvements in performance are highly variable. More robust research has been conducted in nonruminants, where cinnamaldehyde appeared to act as an immune enhancer and capsicum was found to improve blood flow in the gastrointestinal tract. More research is necessary to determine what combinations and dosages of essential oils (might) provide notable benefits to beef cattle producers.

Due to the variability in environmental conditions, diets, stress and physiological status of cattle in a feedlot, it is reasonable to assume that a product containing a blend of probiotics, prebiotics and/or enzymes may best capture the benefits of the various modes of action.

For example, a combination pro- and prebiotic product synbiotic may provide the animal with beneficial microorganisms while also providing substrates to stimulate the growth of the native commensal microorganisms. Talk with your nutritionist about which types of feed additives may be most beneficial to your operation.  end mark

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Aimee Hafla
  • Aimee Hafla

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