Feed efficiency and methane emissions with Ermias Kebreab, UC Davis

The poultry and swine industries have transformed feed efficiency over the past two decades. Through systematic improvement in nutrition, enzyme utilization, and animal genetics, they now produce vastly more protein from  fewer resources.  The challenge is not simply reducing methane emissions from cows, but reducing methane per unit of milk produced while maintaining farmer profitability and food security.

But here's the complexity: feed intake in dairy cattle is difficult to measure in controlled research facilities; in pasture-based systems where 88% of global cattle graze, measurement becomes extraordinarily challenging. Yet without precise data, researchers cannot translate laboratory findings into reliable commercial recommendations. This measurement gap between what science discovers and what farmers can practically implement represents agriculture's critical bottleneck. When you combine this with the variability in dairy systems—roughly 20% natural variation in methane emissions even among genetically similar control animals—the path forward requires nuanced, system-level analysis rather than simple silver bullets.

Today we are joined by Ermias Kebeab from UC Davis, whose research demonstrates that genetic selection offers a permanent, cumulative, and heritable pathway to improved feed efficiency. Kebeab's recent work evaluated the EcoFeed index developed by STgenetics, a genomic breeding value tool based on over 10,000 animals—7,623 growing Holstein heifers and 2,538 lactating cows. Results showed that selecting for improved residual feed intake (RFI) reduces lifetime emissions without compromising productivity. A one-standard-deviation improvement in genomic RFI decreased feed consumption by 2.73% and reduced lifetime CO2 equivalent emissions by 2.42% per animal—equivalent to 868 kg CO2e savings per cow. A three-standard-deviation improvement showed even greater potential, reducing feed intake by 8.2% and emissions by 7.31%, while simultaneously lowering feed costs by $199 per female.

Ermias's research bridges research discovery with practical implementation across both the Global North and Global South. Kebeab's work on grape pomace byproducts—incorporated at 10-15% of dairy rations—demonstrates milk yield improvements alongside methane intensity reductions, while pre-fermenting almond hulls shows additional potential when economic trade-offs are favorable.

Crucially, he emphasizes that the Global South's emissions reduction challenge differs fundamentally from the North. Where dairy systems produce less than 2,000 kg milk annually, the priority must be productivity improvement rather than limiting animal numbers. Rising energy and fertilizer costs disproportionately impact low and middle-income countries, making locally-adapted tropical breeds and resilient farming systems more viable than input-intensive Western genetics. 

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