Implementation of Feed Saved evaluations in the U.S.
Feed efficiency is a trait of significant economic and environmental importance in the dairy industry, and feed accounts for half of the costs of dairy production. Improvements in feed efficiency have the potential to reduce manure and methane outputs, as well as crop and land inputs. Measurements of feed efficiency rely on individual feed intake data however, these data are expensive and time-consuming to collect, resulting in an insufficient phenotyped population. A concerted effort has been underway in the United States for 10 years to collect data for genomic evaluations of feed efficiency. As a result of this effort, the Council on Dairy Cattle Breeding (CDCB; Bowie, MD) provided official evaluations for Feed Saved beginning in December 2020. Feed intake was measured for 4 to 6 wk in individual cows between 50 and 200 days-in-milk in 9 research herds; to date, we have amassed 655,000 daily records of intake and milk production. From these data, residual feed intake (RFI) is estimated with a linear model accounting for milk energy, metabolic body weight, change in body weight, and cohort effects. Current phenotypic data include 6,221 RFI records from 5,023 U.S. Holsteins born 1999 to 2017 (as of December 2020). Phenotypic RFI are used to estimate traditional PTA in a linear animal repeatability model. Deregressed traditional PTA are then used to calculate genomic evaluations of RFI. These evaluations are combined with evaluations for body weight composite (BWC) to provide Feed Saved evaluations to the dairy industry. Progeny-tested bulls have an average genomic reliability of 38% for Feed Saved. Comparatively, young bulls have an average genomic reliability of 28%. Given the expectedly low reliabilities, a primary goal continues to be collecting additional phenotypes. Emphasis is also directed towards ensuring that phenotyped cows have close ties to current bulls actively used by the dairy industry. International collaborations will further expand the reference population. As an example, the next official evaluation (April 2021) will include phenotypic data from Canada for 650 cow-lactations. Preliminary testing has indicated a 1 to 2% increase in genomic reliability from these additional data. Feed Saved is currently published by the CDCB as an individual trait. Future plans include incorporating the trait into an economic selection index.
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