Reducing GHG emissions through genetic improvement for feed efficiency: effects on economically important traits and enteric methane production

Abstract

Genetic selection for residual feed intake (RFI) is an indirect approach for reducing enteric methane (CH4) emissions in beef and dairy cattle. RFI is moderately heritable (0.26 to 0.43), moderately repeatable across diets (0.33 to 0.67) and independent of body size and production, and when adjusted for off-test ultrasound backfat thickness (RFIfat) is also independent of body fatness in growing animals. It is highly dependent on accurate measurement of individual animal feed intake. Within-animal repeatability of feed intake is moderate (0.29 to 0.49) with distinctive diurnal patterns associated with cattle type, diet and genotype, necessitating the recording of feed intake for at least 35 days. In addition, direct measurement of enteric CH4 production will likely be more variable and expensive than measuring feed intake and if conducted should be expressed as CH4 production (g/animal per day) adjusted for body size, growth, body composition and dry matter intake (DMI) or as residual CH4 production. A further disadvantage of a direct CH4 phenotype is that the relationships of enteric CH4 production on other economically important traits are largely unknown. Selection for low RFIfat (efficient, −RFIfat) will result in cattle that consume less dry matter (DMI) and have an improved feed conversion ratio (FCR) compared with high RFIfat cattle (inefficient; +RFIfat). Few antagonistic effects have been reported for the relationships of RFIfat on carcass and meat quality, fertility, cow lifetime productivity and adaptability to stress or extensive grazing conditions. Low RFIfat cattle also produce 15% to 25% less enteric CH4 than +RFIfat cattle, since DMI is positively related to enteric methane (CH4) production. In addition, lower DMI and feeding duration and frequency, and a different rumen bacterial profile that improves rumen fermentation in −RFIfat cattle may favor a 1% to 2% improvement in dry matter and CP digestibility compared with +RFIfat cattle. Rate of genetic change using this approach is expected to improve feed efficiency and reduce enteric CH4 emissions from cattle by 0.75% to 1.0% per year at equal levels of body size, growth and body fatness compared with cattle not selected for RFIfat.

Methane, nitrous oxide emissions and mitigation strategies for livestock in developing countries: A review

“…Thus, genetic improvement of feed conversion efficiency reduces the total manure produced and consequently reduces the emissions of CH 4 and N 2 O while maintaining productivity . In dairy and beef cattle, genetic selection for residual feed intake has shown that this indirect approach to reducing CH 4 emission is moderately heritable (0.26 to 0.43) and moderately repeatable across diets (0.33 to 0.67), indicating that the inclusion of this trait in the TMI could effectively reduce CH 4 emissions (Basarab et al, 2013). In developing countries, where economic resources for selection are insufficient, CH 4 and N 2 O emission reduction from enteric and manure fermentation can be achieved with the financial support of international donors (Arakelyan & Moran, 2015;Samaniego & Schneider, 2015) and with the aggregation of countries that have similar selection interests.…”

Invited review: Improving feed efficiency in dairy production: challenges and possibilities

“…Selection for lower RFI should reduce feed production requirements in confinement dairy systems or permit increased stocking density in grazing systems. Based on models developed by Little et al (2008), selection for reduced RFI over a 25-year period in beef cattle production could reduce the total farm area required to support animal production by 13% and reduce the carbon footprint by 14% (Basarab et al, 2013). Although similar models for the effects of reducing RFI in dairy cattle have not been evaluated, a model evaluating improvements in GFE measured as reduced feed intake for the same level of energy-corrected milk yield indicated that improving GFE by one phenotypic standard deviation should reduce land use required for feed production by 6.7% per cow (or 4.2% for one genetic standard deviation; Bell et al, 2012).…”

“…Generally, as feed intake increases, additional substrate is available for rumen fermentation and methane production (Basarab et al, 2013). Hence, selection for lower RFI should permit significant reductions in methane emissions by decreasing average DMI of the herd.…”

“…Finally, low RFI in cattle potentially is associated with decreased manure output per animal relative to cattle with high RFI due in part to reduced DMI (Basarab et al, 2013;Berry and Crowley, 2013). Therefore, the release of methane and nitrous oxide into the atmosphere from manure management should be reduced by improving feed efficiency among dairy herds.…”

“…In fact, multiple studies report positive phenotypic correlations between RFI measured during growth and feeding rate (quantity of feed consumed per unit of time), number of meals consumed per day and time spent feeding each day by beef cattle (reviewed by Basarab et al, 2013), indicating that the most efficient animals ate at a slower rate, ate less often and spent less time feeding each day compared with the least efficient animals. Likewise, similar feeding trials conducted in growing Holstein-Friesian heifers in both New Zealand and Australia found that the most efficient heifers (lowest 10% for RFI) ate at a slower rate relative to the most inefficient heifers (highest 10% for RFI; Williams et al, 2011;Green et al, 2013), and efficient heifers in the New Zealand study ate fewer meals and spent less time feeding each day compared to inefficient heifers.…”