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There is no silver bullet!

Nutrition with John McKinnon

Recently I was invited by the University of Calgary to give a presentation at their annual beef conference on alternatives to growth promotants. The presentation was part of a larger program that addressed alternative beef production strategies that could be used to access niche markets or used in the future if federal regulatory agencies place restrictions on current technology. While preparing for this presentation, it became apparent that there are a number of conventional management practices as well as several innovative products either on the market or in the R&D stream that address this topic. The following discussion focuses on some of these novel approaches to growth promotion.

Before proceeding however, let’s first look at the growth-promoting products currently used by industry. These include hormonal implants, ionophores, antibiotics, beta-agonists and estrus suppressants. Individually and collectively, these products provide numerous benefits to individual producers as well as to the industry as a whole. Benefits include superior weight gains, improved feed efficiency, heavier, leaner carcasses and reduced morbidity and mortality. With respect to the industry as a whole, these products allow for more beef to be produced from fewer cattle, thus reducing the industry’s environmental footprint. I point these benefits out simply to show that any alternative product or management strategy has large shoes to fill in terms of its impact on the industry.

Bearing this in mind, the question becomes: What are the alternatives and how effective are they? In terms of research, there were several areas of current activity that were discussed at this conference including enhanced disease management (i.e. immune stimulation, alternatives to antimicrobials, alternative weaning and marketing strategies), genetic advancements (i.e. sire selection, feed efficiency), and nutritional and alternative production strategies. This discussion will focus on the latter of these research areas.

Today’s practice of feeding high grain diets to finishing cattle promotes high rates of gain, efficient feed utilization as well as high-quality carcasses. They also increase the incidence of metabolic diseases such as sub-acute acidosis, which in turn can lead to issues with liver abscesses and laminitis. In order to control these digestive upsets, it is common to feed ionophores (i.e. monensin, lasalocid) as well as certain antibiotics such as tylosin or oxytetracycline. Ionophores lead to more efficient gains by promoting a stable rumen fermentation, by altering rumen fermentation/microbial activity, and by reducing energy losses through reduced methane emissions.

Essential oils are plant extracts with antimicrobial activities that have been proposed as potential replacements for ionophores. There are numerous plants that yield such compounds including cinnamon (bark), rosemary, garlic, coriander (seeds), orange (peel) and tea trees. Research has shown that some of these extracts influence rumen fermentation in a manner similar to ionophores, in that rumen nitrogen and energy use is improved and in some cases methane production is inhibited. These extracts can be fed individually or as a blend; however, to this point Canadian research has not shown consistent production responses with beef cattle. For example, work conducted by Agriculture and Agri-Food Canada with an extract of the cinnamon tree (cinnamaldehyde) showed that relative to a control, cattle fed this extract had increased feed intake in the first 28 days of the feeding period; however, there was no benefit in terms of feed efficiency nor when performance was evaluated over the entire trial.

There has also been considerable research into the use of various bacterial and fungal products as either prebiotics (dead cells or fungal extracts) or probiotics (live bacterial or yeast cells). An extract of the mould Aspergillus oryzae is an example of a prebiotic that has been commercially available for a number of years. Yeast products are typically comprised of live or dead cells of the fungi Saccharomyces cervisiae. Widely used in the dairy industry, both products are reported to alter microbial growth/fermentation and enhance fibre digestibility. Under some feeding situations, these products have been shown to improve feed efficiency in feedlot cattle.

While the above products focus on rumen microbial function they have not been shown to influence the occurrence of liver abscesses in feedlot cattle. As mentioned above, liver abscesses are a consequence of high grain feeding and several studies have shown that their occurrence is a reflection of the forage level in the diet. For example, increasing forage levels in finishing diets from five to 10, to 20 and to 30 per cent can dramatically reduce their incidence. However, performance is also reduced due to lower dietary energy levels. Recent research at the University of Saskatchewan has shown that manipulation of dietary forage levels in backgrounding diets can lead to compensatory gain in cattle fed higher forage finishing diets. Such dietary manipulation might be one way of obtaining higher forage inclusion levels throughout the feeding period and reduce the need for antibiotics to control the occurrence of liver abscesses. Research has also focused on vaccine development; however, results with commercially available products have been variable, particularly under aggressive feeding conditions.

As is evident from the above discussion, considerable effort has been directed at finding alternatives to the growth-enhancing technology used by industry. While there has been progress, no silver bullet exists that provides the consistent performance benefits of current technology.

About the author

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John McKinnon is a beef cattle nutritionist at the University of Saskatchewan.

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