Date of this Version
Heritabilities and genetic correlations were estimated for milk and fat yields and fat percentage from 305-d, mature-equivalent records of registered and grade Holsteins in California, New York, and Wisconsin. Parameter estimates were obtained with daughter on dam regression within herd-year-season and sire of daughter. Data were pairs of first lactation records (38,115 in California, 171,555 in New York, and 136,031 in Wisconsin) from 1975 through 1984. California had higher means for milk (9046 kg) and fat (323 kg) than the other two states (approximately 7840 kg and 289 kg), but heritabilities of .36 and .34 were not greatly different from those for New York (.34 and .33) or Wisconsin (.38 and .35). Heritability of fat percentage, however, was smaller for California (.55 vs .66 for New York and .68 for Wisconsin). Logarithmic and square root transformations of the data resulted in little change in heritability estimates. For California, genetic correlation between milk and fat yields (.70) was larger than for New York (.55) or Wisconsin (.56), and correlation between fat yield and fat percentage was smaller (.31 vs .45 and .41). For each state, estimates of heritabilities were larger for registered than grade pairs.