Heritabilities for Lactation Average of Somatic Cell Counts in First,Second, and Third or Later Parities

Heritabilities were estimated for lactation average log, base 2, somatic cell count from cows with four or more tests in each lactation. Estimates were for first, second, and third or later parities (defined by age at calving) individually and for mixed parities. Estimates were from sire components of variance with numbers of sires and daughters of 406 and 22,140; 337 and 8,659; 311 and 6,122; and 310 and 10,217 for mixed, first, second, and third or later parities, respectively.Both sire and error components of variance increased with parity. Heritabilities were .18, .09, .10, and .29, for mixed, first, second, and third or later parities.