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- Are All Genomic Tests Created Equal?
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- Feed Saved
- Your Genomic Results: Milk Them for All They’re Worth
Feed efficiency in dairy cattle is of interest to dairy producers and environmental advocates around the world. Feed efficient cows generate higher income over feed costs and have a smaller carbon footprint than cows that are less efficient.
Although specific genetic evaluations for feed efficiency are new, the genetic selection for efficiency is not. Dairy producers around the world have selected for increased efficiency for decades by focusing on increased milk production per cow and, more recently, decreased body size. Today, the carbon footprint for a liter of milk produced in the U.S. is two-thirds smaller than it was 70 years ago. The U.S. is producing 60% more milk with 16 million fewer dairy cows than in 1950. This trend for higher volumes of milk produced by fewer cows is seen around the world, as producers continually strive for improved efficiency through better genetics and management practices.
Feed efficiency in dairy cattle is defined as the value of milk produced minus the cost of feed required for maintenance and production. The challenge in developing a genomic evaluation for feed efficiency is the inability to easily measure daily intake, body weight and milk production of individual animals in the herd environment. In collaboration with USDA-AIGL, and four U.S. universities, CDCB has developed the first genomic evaluation for Residual Feed Intake (RFI) and Feed Saved (FSAV).
Residual Feed Intake (RFI) and Feed Saved (FSAV)
Calculating Residual Feed Intake (RFI) requires daily measurements of feed intake, body weight and milk production among animal cohorts. As of November, 2020 there are 6,231 Holstein cows with feed intake data and genotypes in the database contributing to the genomic RFI evaluation.
Unlike the Feed Efficiency (FE) evaluation, which is expressed as the economic advantage of feed efficiency, Feed Saved (FSAV) incorporates genomic evaluations for Residual Feed Intake (RFI) rather than related values for milk, fat and protein production, and will be expressed in pounds of dry matter saved per lactation.
PTA FE (USD) = (-0.0248 x PTA Milk) + (1.16 x PTA Fat) + (2.18 x PTA Protein) – (12.4 x BWC*)
PTA FSAV (pounds of dry matter) = (-138 x BWC*) + (-1 x PTA RFI)
*BWC = (0.23 x Stature) + (0.72 x Strength) + (0.08 x Body Depth) + (0.17 x Rump Width) – (0.47 x Dairy Form)
Lifetime value of Feed Saved = $0.12/pound DM x 2.6 lactations = $0.31/pound of feed saved
In practical terms, a bull who is +100 PTA FSAV is expected to have daughters who will consume 100 pounds less dry matter per lactation than the average cow. This equates to an economic benefit of $12 per lactation or $31 lifetime. RFI and FSAV evaluations are only available for Holsteins and reliabilities are low (15% and 37% respectively). However, research is ongoing, and reliabilities will improve as data is added. The Holstein NM$ formula will be updated in April 2021 to include Feed Saved (FSAV).
Summary
Residual Feed Intake and Feed Saved are valuable evaluations that provide greater insight into improving feed efficiency in dairy cattle. However, feed efficiency alone is not the goal of most producers, but rather increasing income over feed costs. For this reason, these traits should be used within a total merit index that accurately accounts for all the traits associated with profitability.