Microbiome research is an area of increasing interest in livestock production due to potential microbiome impacts on animal performance. The term microbiome, while scientifically rooted in the genetic makeup of the microbes, is used to more generally represent the microbial populations that are present in an environment. Cattle, for instance, have microbial populations in their rumens that degrade the feedstuffs consumed, producing nutrients that can be absorbed and metabolized by the host for production of meat, milk, and fiber. The amounts and types of nutrients produced by the microbial populations, and thus absorbed by the host can vary, however, depending on the composition of microbes present. This variation in nutrient production and absorption likely contributes to variation in animal performance, and while most rumen microbiome research has focused on live-production traits, an area of importance that has received little investigation is the relationship between the rumen microbiome and adipose tissue development in the carcass.
Beef cattle carcass value is influenced by the quality and quantity of meat produced, both of which are related to the fat: lean ratio. The difference, however, lies mostly in the location where fat accumulates. For instance, a major determinant of a beef carcass’ USDA quality grade is the amount of intramuscular fat deposited in the longissimus muscle, such that greater amounts of intramuscular fat are associated with higher quality grades (Prime>Choice>Select>Standard). In September 2020, Prime carcasses received a $12.17/cwt premium, while Select and Standard carcasses received discounts of $12.94/cwt and $26.77/cwt, respectively. In contrast, the quantity of meat produced, as estimated by the USDA yield grade, is largely influenced by the amount of subcutaneous and intermuscular fat, with less fat in these deposits being more desirable (1>2>3>4>5). Again, in September 2020, yield grade 1-2 and 2-3 carcasses were awarded a $3.79/cwt and $1.68/cwt premium, whereas yield grade 4-5 and 5+ carcasses were discounted by $12.00/cwt and $17.57/cwt, respectively. Ultimately, these trends suggest that high yielding carcasses with higher meat quality are desired, which means our goal, in terms of adipose tissue, is to produce carcasses with increasing intramuscular fat while minimizing subcutaneous and intermuscular fat.