USDA Updates Economic Values for Lifetime Merit Indexes
Reflecting forecasts for higher milk prices, lower feed costs and improved cull cow prices, yield traits will receive more relative emphasis compared with Productive Life, Body Size Composite and Somatic Cell Score (SCS). Furthermore, considerable changes in somatic cell premiums and penalties in the USA has led to changes in the cow population for genetic averages and variation for SCS, also contributing to a lower weighting within Lifetime Net Merit (LNM$). Slight revisions were made to milk component prices, increasing the ratio of Protein relative to Fat. With the addition of Cow Conception Rate and Heifer Conception Rate to the indexes, overall weighting on fertility traits stays approximately the same when combined with Daughter Pregnancy Rate.
LNM$ and the two variations of Cheese Merit (CM$) and Fluid Merit (FM$) specific to differing milk markets are selection indexes used to rank dairy bulls of each breed based on economic merit for lifetime profitability. The table below details the traits included in the Lifetime Merit indexes and their respective relative weightings.
Using data from a study of economic conditions for grazing herds done by Purdue University researchers, USDA-AGIL also developed a Grazing Merit (GM$) index to aid pasture-based dairy producers in selecting genetics to aid in seasonal calving systems. Relative trait weightings are included in the table below. GM$ values are available on all dairy bulls with public evaluations in the USA.
TPI® Changes Emphasize Fertility, Include Body Size Composite
The Holstein Association announced TPI formula revisions implemented with the December 2014 evaluations, stating the changes bring more focus on some important traits.
Daughter Pregnancy Rate (DPR) is combine with Cow Conception Rate (CCR) and Heifer Conception Rate (HCR) in a new Fertility Index, a sub-component of TPI. The Fertility Index has a ratio of two-thirds weightings on DPR and one-third each on CCR and HCR.
Additionally, using the same factors applied to Lifetime Net Merit, a Feed Efficiency value is being published to account for the difference in the dollar value of milk produced and the feed costs associated with production and body size.
By adding new traits and changing the emphasis on fertility, the relative weighting has decreased by 1% for Udder Composite, 2% for PTAT-Final Score and 2% for Productive Life.
Jersey JPITM Formula Updates Result of University Research
Referred to as "the most extensive evaluation of production, longevity and health data ever undertaken," the AJCA-funded research completed by Dr. Kent Weigel of the University of Wisconsin-Madison has promoted changes to the Jersey Performance IndexTM (JPI) effective with the December 2014 evaluations.
Weigel used records from more than 300,000 Jersey cows born since 2001 to analyze the strengths and weaknesses of the U.S. Jersey cow population. Using the conclusions, the AJCA staff and board of directors modified the JPITM formula to set the stage for a strategy of breed improvement in the years to come. Areas of focus include a slight shift toward Protein relative to Fat and an added emphasis on cow fertility by increasing the emphasis on Daughter Pregnancy Rate and adding Cow and Heifer Conception Rates.