Invited review: Improving feed efficiency of beef cattle – the current state of the art and future challenges

Abstract

Improvements in feed efficiency of beef cattle have the potential to increase producer profitability and simultaneously lower the environmental footprint of beef production. Although there are many different approaches to measuring feed efficiency, residual feed intake (RFI) has increasingly become the measure of choice. Defined as the difference between an animal's actual and predicted feed intake (based on weight and growth), RFI is conceptually independent of growth and body size. In addition, other measurable traits related to energy expenditure such as estimates of body composition can be included in the calculation of RFI to also force independence from these traits. Feed efficiency is a multifactorial and complex trait in beef cattle and inter-animal variation stems from the interaction of many biological processes influenced, in turn, by physiological status and management regimen. Thus, the purpose of this review was to summarise and interpret current published knowledge and provide insight into research areas worthy of further investigation. Indeed, where sufficient suitable reports exist, meta-analyses were conducted in order to mitigate ambiguity between studies in particular. We have identified a paucity of information on the contribution of key biological processes, including appetite regulation, post-ruminal nutrient absorption, and cellular energetics and metabolism to the efficiency of feed utilisation in cattle. In addition, insufficient information exists on the relationship between RFI status and productivity-related traits at pasture, a concept critical to the overall lifecycle of beef production systems. Overall, published data on the effect of RFI status on both terminal and maternal traits, coupled with the moderate repeatability and heritability of the trait, suggest that breeding for improved RFI, as part of a multi-trait selection index, is both possible and cumulative, with benefits evident throughout the production cycle. Although the advent of genomic selection, with associated improved prediction accuracy, will expedite the introgression of elite genetics for feed efficiency within beef cattle populations, there are challenges associated with this approach which may, in the long-term, be overcome by increased international collaborative effort but, in the short term, will not obviate the on-going requirement for accurate measurement of the primary phenotype.

Review: Fifty years of research on rumen methanogenesis: lessons learned and future challenges for mitigation

“…Another approach for lowering CH 4 emissions through animal genetics is the selection of more efficient animals based on a measure of feed conversion efficiency such as residual feed intake (which compares the actual feed intake of animals to expected intake for maintenance and production; Kenny et al, 2018). This trait is moderately heritable (0.26 to 0.43) and moderately repeatable across diets (0.33 to 0.67) (Basarab et al, 2013), although there is evidence that animal re-ranking may occur with different types of diets (Kenny et al, 2018). One limitation for research is that the measurement of residual feed intake requires accurate measurement of DMI of individual animals, which is challenging for grazing animals.…”

Metatranscriptomic Profiling Reveals the Effect of Breed on Active Rumen Eukaryotic Composition in Beef Cattle With Varied Feed Efficiency

“…Many factors can affect feed efficiency, including animal genetics, nutrition, biology, physiology, metabolism, behavior, etc. (Kenny et al, 2018). Although it is not well defined, the digestive activity of animals likely contributes to about 10% of the variation in feed efficiency (Richardson and Herd, 2004).…”

A Meta-Analysis of the Effects of Slow-Release Urea Supplementation on the Performance of Beef Cattle

“…There is a vast diversity in the efficiency of beef production systems, which creates opportunities for reducing the global environmental impacts of beef production [39]. Feed efficiency is increasingly recognised as a significant tool for reducing the environmental footprint of beef production due to its beneficial effect in improving resource use efficiency per unit product and reducing enteric methane emission [40,41]. Interestingly, there is a positive relationship between FE and environmental footprint and economic sustainability, suggesting that strategies that improve the FE of beef cattle could lead to a simultaneous improvement in environmental impacts and profitability of beef production [41].…”

“…Feed efficiency is increasingly recognised as a significant tool for reducing the environmental footprint of beef production due to its beneficial effect in improving resource use efficiency per unit product and reducing enteric methane emission [40,41]. Interestingly, there is a positive relationship between FE and environmental footprint and economic sustainability, suggesting that strategies that improve the FE of beef cattle could lead to a simultaneous improvement in environmental impacts and profitability of beef production [41]. Dietary strategies and nutritional technologies have been demonstrated as potential tools to improve FE and reduce the environmental impacts of livestock production [42][43][44].…”