PERFORMANCE AND GENETIC TRENDS IN PUREBRED SIMMENTAL FOR REGIONS OF THE UNITED-STATES

A study was conducted to determine whether differences in regional per formance could be attributed to different selection goals among Simmen tal breeders. Using data obtained from the spring 1993 National Simmen tal Cattle Evaluation, breeders were identified by region of the count ry as defined by the American Simmental Association: South Central (SC ), North Central (NC), West (W), and East (E). Animals included in the analysis were at least 87.5% Simmental and from breeders who recorded data every year from 1978 to 1991. The number of breeders and animals from each region were 154 and 62,830 in the SC, 260 and 139,053 in th e NC, 102 and 57,434 in the W, and 143 and 39,786 in the E. Phenotypic , genetic, and environmental trends were estimated in each region for birth weight (BWT), weaning weight (WWT), and postweaning gain (PWG). The growth genetic trends were increasing at similar rates in the regi ons over time. For maternal milk (MMK), breeders in the NC and W decre ased maternal breeding value slightly compared to SC and E breeders. F or BWT, the average environmental; trends ranged from .0 kg/yr in the SC to .11 kg/yr in the NC. The regional WWT environmental trend ranged from 1.4 to 2.2 kg/yr. The environmental trends for PWG varied from - 3.1 kg/yr in the SC to .3 kg/yr in the W. Selected parents had higher estimated breeding values than their birth year averages each year for BWT, WWT, and PWG. The average maternal breeding values for selected parents were essentially zero compared with their birth year averages. Most of the regional phenotypic differences were attributed to differ ences in average environment, not the result of different selection go als among Simmental breeders.