January genetic base change may be smaller than expected

This January will usher in the seventh genetic base change for U.S. dairy cattle populations. Given the high production PTA (predicted transmitting ability) for many Holstein breed leaders, one would think the base change for traits would be quite high. In the Holstein breed alone, the top bulls were plus 2,964 pounds of milk, 89 protein, 106 fat, 4.32 type, 3.62 udders, and 4.06 for feet and legs in the April USDA sire summaries.

While the top bulls keep getting better, remember that base changes are made in relation to the average cow born for a given year. And for the next base change, that comparison will be made to cows born in 2005. With that in mind, USDA officials tell us that the change for PTA milk will range from 53 to 416.5 pounds for all breeds with Holstein leading the group with the biggest adjustment. Other key traits include protein ranging from 3 to 13.5 pounds; fat, 2.5 to 17 pounds; type, 0.2 to 0.87 points; and udders 0.25 to 0.85 points. In all these categories, Holsteins have the biggest adjustment except for fat where Jersey leads the pack.

While most of the change has been positive, some measurements among health traits were mixed. Daughter Pregnancy Rate (DPR), for example, actually posted a drop. Only one breed, Ayrshire, posted a gain in this area. Meanwhile no significant change was posted in somatic cell score (SCS). On a positive note, Productive Life (PL), the cow's ability to live a long life, rose 0.06 to 0.81 with the Milking Shorthorns tops among the six dairy breeds.

Look for all of these adjustments and many others in the January 2010 sire summaries.