Table 1. Estimated base change for the August 2000 USDA evaluations.

(http://aipl.arsusda.gov/memos/html/base.html)

¹SCS includes phenotypic and genetic change. The changes in PTA SCS due to genetics were near zero in all breeds.

Base Change for Type As Well

The breed associations will also update the genetic base that they use for evaluating conformation traits. They will use the same definition as USDA uses; the average PTA of cows born in 1995. Table 2 shows the expected base change for various type traits.

Table 2. Estimated base changes for conformation evaluations.

(For non-Holstein breeds see http://aipl.arsusda.gov/memos/html/tbase.html;

for Holsteins, see http://www.holsteinusa.com/html/basechange.html)

Impact on Selection Decisions

This periodic update of the genetic base provides a good opportunity to review the progress of your herd or your breed. As you can see, progress over the last five years has led to improvement for most traits. However, not all traits in every breed have been improved. This may be a good time to review your breeding program so that the available information is used to improve the traits you feel are vital to your continued success.

The base change affects all animals equally and does not change how animals rank. The values you see in August will be a little lower, but any ranking changes will be the result of data from additional offspring. If your current practice is to select from the top-ranked animals, you can continue this practice and the base change will have no impact on your decisions. If you are used to establishing minimum requirements for PTA’s like +2,000 PTA milk, +1.00 PTAT and +1.00 for udder composite, those thresholds may need to be re-evaluated. With the base change, fewer animals will meet those criteria, and mating options may be limited if those criteria are too strict.

True Protein

All genetic evaluations for protein will measure true protein beginning in August 2000. Most US farmers are now paid for the true protein they produce as opposed to the traditional crude protein measurements. True protein is a better measure of the food value of milk. Beginning May 1, 2000, all US milk-recording laboratories began reporting true protein values as part of DHI records. USDA will convert the historical crude protein data to true protein, supplement it with the newly collected true protein data, and use the combined data for genetic evaluations. The resulting PTA’s will be expressed on a true protein basis.

The change to true protein will only have a small impact on PTA’s. In fact, PTA’s for protein percentage will be the same. The range of PTA’s for pounds protein will be slightly smaller, and those bulls with high PTA’s for protein % will receive a small boost (table 3). All in all, the change to true protein will cause little re-ranking. The correlation between PTA true protein pounds and PTA crude protein pounds is 0.9993.

The biggest impact of switching to true protein measurements will be in publishing and interpreting lactation records. As the industry works through the transition to true protein, how protein production totals are published may vary. The difference between true and crude protein is small. If a high degree of precision is required, users should be sure to check which measurement is published so that comparisons are made on the same scale.

Table 3. Impact on PTA's of changing to true protein.

Conformation to be part of PL for all Breeds

Since July 1994, USDA has combined PTA’s for type and yield traits with culling information to produce multi-trait PL PTA’s for Holstein sires. In August 2000, these procedures will be extended to Holstein cows and to other breeds. Use of type and yield traits improves the accuracy of PL PTA’s early in an animal’s lifetime when culling information is minimal.

Improvements will also be made in how the type and yield traits are used to predict PL. For Holsteins, PTA’s for milk, fat, protein, SCS, udder composite, feet and legs composite and body size composite will be used to give an early estimate of PL. The same traits will be used for the other breeds except that foot angle will replace feet and legs composite. Those new prediction procedures should improve the reliability and consistency of PL PTA’s.

New Lifetime NM$

The most efficient way to manage the mass of genetic evaluation information and make effective selection decisions is to use a selection index. Based on input from researchers and industry, USDA is implementing an improved NM$ index with the August 2000 evaluations. The objective of the index is to rank animals based on their genetic ability to transmit lifetime net profit.

NM$ will continue to combine PTA’s for milk, fat, protein, SCS and PL, but it will be enhanced by the addition of udder composite, feet and legs composite and body size composite. Those traits will be combined in a way that will generate genetic improvement for yield and PL while holding the line on SCS, feet and legs, udders, and size.

Table 4 includes examples of the new lifetime NM$ for Holstein sires that were used as sires of sons in 1996. Probably the most notable change is that the values for lifetime NM$ are substantially higher because they are expressed as profit over the daughter’s lifetime. Previous NM$ values were expressed on a lactation basis. The average for lifetime NM$ of active AI Holstein sires will probably be around $300. The top Holstein sires will likely have NM$ values near $700.

Table 4. Projected lifetime NM$ for past sires of sons.

Another major change in NM$ is that the value of milk components has been adjusted to reflect current economics. Values for fat and protein have been increased while the value of milk has been decreased. The fluid merit and cheese merit indexes will be enhanced similarly to NM$ and will continue to be provided. Those indexes also will reflect an increased value on the solids portion of milk and a decrease value for the fluid portion.

The most influential traits in the lifetime NM$ index are PTA protein and PTA fat followed by PTA PL, PTA SCS, and udder composite. As displayed in table 4, those bulls that are extremely good for these traits tend to improve their ranking. Those bulls that have a deficiency in one of those traits tend to go down in ranking. Overall the new lifetime NM$ does not drastically re-rank sires but does favor bulls that transmit high component yields along with good PL and good udders.

Summary

The August 2000 evaluations will definitely have a new look. The changes are designed to account for the steady rate of improvement being made in dairy cattle. They also intensify the focus on producing profitable cattle. Those changes provide a good opportunity to review breeding programs and to implement improvements where necessary. Being prepared for the changes coming in August will help you take advantage of these improved genetic evaluation tools.