Feed accounts for 40–60% of total expenses of beef and dairy cattle production costs. Therefore, feed-efficient cattle have a great potential to reduce production costs without compromising meat or milk production levels, resulting in a greater profit margin for producers. Many approaches for measuring feed efficiency are available with residual feed intake being one of the most common. The residual feed intake is defined as the difference between actual dry matter intake and expected dry matter intake based on animal size and production level. Therefore, compared with a least-efficient animal, the most-efficient animal would have a negative residual feed intake coefficient value, indicating that it consumed less dry matter intake while maintaining the same level of production. Recent studies have focused on investigating changes in key metabolites and proteins that would shift metabolic pathways to support better feed efficiency. Recent reports highlighted that in most-efficient cattle metabolic pathways associated with energy, vitamins, and amino acid metabolism in rumen and skeletal muscle are upregulated to provide extra energy, thus, allowing for a similar level of production despite lower dry matter intake. Other studies demonstrated that most-efficient cattle reduce protein turnover in skeletal muscle including upregulation of key protein synthesis pathways, such as mechanistic target of rapamycin signaling, and the downregulation of key proteins in protein degradation such as ubiquitin-proteasome pathway, resulting in greater protein deposition in muscle. In this chapter, we discuss applications of novel comprehensive techniques for protein and metabolite profiling in rumen, intestine, blood, liver, and skeletal muscle to elucidate adaptive biological functions that support better feed efficiency in beef and dairy cattle. |
