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.
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). Because a favorable response to genetic selection for milk, fat, and protein yields as well as somatic cell score (mastitis resistance) and productive life (longevity) could be demonstrated for individual dairy herds, the study was expanded to evaluate how frequently observed dairy cow fertility conformed to genetic expectations for herds of varying sizes. Calving intervals were obtained for over 1 million sire-identified Holstein cows that calved from 2005 through 2009 in over 3,200 Pennsylvania herds. The top and bottom 25% of cows for average of parents’ genetic merit (PA) for daughter pregnancy rate were identified within each herd and calving year. The average PA for daughter pregnancy rate for the top 25% was 1.6%, whereas the average PA for the bottom 25% was -2.0%. A majority of herd-years (80%) had improved fertility for the top PA group compared with the bottom group. For herd-years with 100 cows or more in each top and bottom PA group, 96% met expectations. Across all herd-years, calving interval decreased by 25.4 days for cows with high PA for daughter pregnancy rate compared with the low PA group, which exceeded the expected difference of 14.6 days. Approval was received from a dairy records processing center to use information from Pennsylvania herds under its processing in an August 2011 demonstration at Ag Progress Days, Pennsylvania's largest outdoor agricultural exposition. Producers who provided their herd codes were able to see the value of genetic selection from response to selection within their own herds. Results were also shared at a meeting with administrators of the Lancaster Dairy Herd Improvement Association (DHIA), and approval to allow further development of a web application for Lancaster DHIA herds was obtained. Work toward demonstrating the impact of genetic selection on feed efficiency also began in spring 2012. Fecal samples were taken from 150 dairy cows in the Pennsylvania State University research herd and are currently undergoing processing to determine which cows digested their feed most completely. Subsequent work will determine how genetic selection for yield and other traits impacts diet digestibility.