Evaluation of animal variability in fibre digestion and strategies to improve forage use in beef cattle diets

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Improving feed efficiency is of great interest to the beef industry as it can increase producer profitability and lower the environmental footprint of beef production. Because forage is generally more expensive per unit of available energy than concentrates, and cattle feed efficiency and performance is reduced with the increase forage content in diets, most feedlots feed high-concentrate, low-forage diets (10% or less of DM as forage; Samuelson et al., 2016). However, such diets can increase the incidence and severity of digestive disorders (i.e. acidosis, rumen parakeratosis, liver abscesses, and bloat; Vasconcelos and Galyean, 2008). To mitigate risk for these disorders and to increase feed efficiency, in feed antimicrobials such as ionophores and antibiotics are commonly added to feedlot diets. With increasing regulations restricting the use of in feed antimicrobials, it is important to develop new strategies that can maintain or improve feed efficiency and producer profitability, and at the same time improve animal health and welfare. If the efficiency of fibre digestion of forage sources can be improved, it could be possible to improve feed efficiency, profitability, and animal health by increasing concentrations of forage in feedlot diets. Hence, the long-term goal of my research program is to improve the efficiency of fibre digestion, and consequently the performance and health of beef cattle. My research over the next five years will address four short-term objectives: 1) investigate the relationship of animal physiological and rumen microbiological parameters with the ability of cattle to digest fibre; 2) investigate the interaction of rumen inoculum of cattle with divergent ability to digest fibre with ruminal pH and with solids passage rate on ruminal fermentation parameters; 3) investigate if cattle selected for greater fibre digestibility on a high grass hay diet also has greater fibre digestibility when fed a high concentrate diet, and when fed a different forage source; and 4) investigate if calves selected for greater ability to digest fibre actually have improved growth performance and feed efficiency. I am interested in understanding the effect that microbe-host interactions have on gastrointestinal physiology in beef cattle that are more efficient at digesting fibre. Maximizing the ability of cattle to use forages and digest fibre can reduce the use of grain that could be used to feed humans, improve the utilization of available forage sources and low quality cereal residues, and increase feed efficiency, consequently increasing the economic and environmental sustainability of beef production. In addition, the knowledge generated on the complex and orchestrated action of the rumen microbes to degrade recalcitrant lignocellulose may have implications for other industries like the production of cellulosic biofuels and feed enzymes.