We all have heard the common concern facing global food security: The demand for a high-quality protein source is expected to increase with a rapidly increasing population. Increasing the feed efficiency of beef cattle is one of the most promising efforts aimed at improving the environmental sustainability of beef production through reduced use of inputs and a reduction in greenhouse gas production. In beef production, we are most familiar with feed efficiency defined as the amount of feed required per pound of gain. This complex phenotype is reliant on the microbes that live in and feed the host animal. Indeed, feed efficiency in cattle considers the rumen microbes’ ability to convert what would be considered low-quality feed options for humans into a high-quality product like milk, meat and feed-efficient calves.
Different operations, different production focuses
Different production sectors within the beef cattle industry have a unique definition of what is considered a quality end product. With that, different management practices are implemented to ensure that every opportunity to meet production goals are offered. Feedlots, for example, are focused on cattle growing muscle tissue and increasing fat deposition. Highly concentrated diets are commonly offered as the most efficient way to meet nutritional requirements in this operation. Cow-calf producers, on the other hand, are more focused on maintaining cow health, body condition, encouraging fetal growth and having a cow raise a healthy, profitable calf. Importantly, cow-calf operations are more commonly maintained on a forage-based system, where the intent is to set the calf up for success by being as efficient as possible through the various stages of life and production.
Historically, there has been a heavy focus on studying steers’ rumen environment and feed efficiency through different production stages. These animals, in most cases, are managed in a way that promotes growth and muscle development in the most cost-efficient way possible. Previous studies have utilized technologies and different management practices – including a variety of feeds, supplements, ionophores and growth-promoting implants – to determine their respective impacts on rumen microbiome health and resultant feed efficiency differences. However, very few studies are reversed to investigate the female’s status through her stages of production, especially during pregnancy.
The heifer and cow are key
A productive cow is the most important asset to a profitable cattle producer’s herd. Although there is a higher expectation of profit and value in a market animal, without a successful pregnancy on the cow’s part, there would be no animal to market. Ideally, a cow is a long-term constituent of a herd and is a consistent contributor of genetic attributes for the next generation of cattle, and it is important to gain a better understanding of the rumen environment to continue to improve the cow-calf enterprise.
Several recent research projects have focused on the importance of heifer and cow feed efficiency research, specifically taking into account the importance of the rumen environment. For example, our group has recently identified several rumen bacteria and blood metabolites that are important in feed-efficient heifers, which could help to identify more efficient animals. As feed efficiency and rumen microbes have been demonstrated to be moderately heritable, these efficient cattle are important for the development of efficient calves. Further, as methane emissions represent a gross energy loss from feed intake, our group at the University of Tennessee and collaborators have shown that in drylot cow-calf systems, where adding ionophores such as monensin to the diets of beef cattle is common, methane emissions were not reduced long-term when animals were fed monensin in confinement. Despite prior studies that have used steers to establish methane mitigation methods, the use of steers reduces the potential for long-term methane reductions in the industry. Replacement heifers have greater longevity than market steers and are therefore important for methane and feed efficiency research.
Efficient females are the future of beef production
Pregnancy in beef cattle is of the utmost importance to producers where it is optimal to have cows that can produce efficient calves and maintain a stable, efficient rumen through stages of production. Given that these cattle contribute to the propagation of genetics in the herd, understanding feed efficiency in heifers and cows is essential for cattle production. It is important for future work to determine the changes occurring within the female’s rumen environment and understand the impact they have on the host. This period of the animal's life is critical, and meeting the energy requirements during this period will aid in determining the efficiency of nutrient utilization she has for the rest of her life and for her resultant offspring. Furthermore, it is just as critical for producers to implement strategies regarding feed efficiency based on their production goals to remain profitable and productive. By considering all constituents of the herd, we can continue to improve the sustainability of beef production long-term.
Gabbi Martin contributed to this article. She is a graduate student in the department of animal science at the University of Tennessee.
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