1a. Objectives (from AD-416)
Determine traits that would benefit most from expanded educational efforts. Develop computer programs to illustrate how daughters of superior bulls nationally for the traits of interest deliver an advantage within an individual producer’s own herd. Promote the development of an efficient and healthy national dairy herd through demonstration of genetic selection results. Provide a convenient way of using the software developed for extension type meetings of dairy producers.
1b. Approach (from AD-416)
Records from the national dairy database will be shared with PSU cooperators. Existing AIPL programs will be modified to identify the top and bottom quartile of cows each year based on sire PTA + 1/2 MGS PTA. The performance of the top and bottom quartiles will be compared. The number of observations needed to reliably demonstrate that genetic selection results in superior performance will be determined. Web applications will be developed that will allow users to query the AIPL database for herd specific results, including performance charts for each trait with a link to the cows and sires in each group. Demonstrate the tool to producer groups.
3. Progress Report
The project is related to in-house objectives 2 (characterize phenotypic measures of dairy practices and provide the industry with information for determining impact of herd management decisions on profitability) and 3 (improve accuracy of prediction of economically important traits currently evaluated). A study was conducted to evaluate how frequently observed animal performance conformed to genetic expectations for various traits and for herds of varying sizes. Parent averages and standardized records for milk, fat, and protein yields as well as somatic cell score (mastitis resistance) and productive life (longevity) were obtained for over 1 million sire-identified Holstein cows that calved from 2005 through 2009 in over 3,300 Pennsylvania herds. The top and bottom 25% of cows for parent average were identified within each herd and calving year for each trait. Average milk, fat, and protein yields, somatic cell score, and productive life for the top and bottom parent-average groups were determined for all herd-years. Observed performance conformed to expectation when average performance for the top parent-average group exceeded that for the bottom group. A majority of herd-years had better performance for the top parent-average group than for the bottom group. Average difference in parent average for fat yield between the top and bottom parent-average groups was 34 kg, which was close to their phenotypic difference of 36 kg. For productive life, average parent-average difference between top and bottom groups (4.8 months) was greater than their phenotypic difference (1.5 months). More than 89% of herd-years met expectations for yield traits when more than 10 cows were in each of the top and bottom parent-average groups compared with 74% for somatic cell score and 67% for productive life. For herd-years with 125 cows or more in each top and bottom parent-average group, 100% met expectations for yield traits compared with 98% for somatic cell score and 68% for productive life. Within-herd comparison of top and bottom cows for parent average demonstrated a favorable response to selection for yield traits even in herds with relatively few sire-identified daughters. Results were less predictable for traits with lower heritabilities, but the majority of herd-years still conformed to expectations. A scientific abstract was published. Approval was received from a dairy records processing center to use information from Pennsylvania herds under its processing in an August demonstration at Ag Progress Days, Pennsylvania's largest outdoor agricultural exposition. Producers who provide their herd codes can see the value of genetic selection from response to selection within their own herds. Monitoring activities for the project included discussions with the Cooperator at jointly attended activities as well as several phone calls and e-mail exchanges of results produced by the project. Results were shared with three committees of the National Association of Animal Breeders in April 2011.