Response to Selection of United States Holstein Sires in Latin America

Abstract

Milk yield was regressed on sire PD for 28,755, 65,990, and 30,279 sire identified records from Colombia, Mexico, and Puerto Rico. Milk yields were expressed as daughter herd-year deviations for projected or actual 305-d milk yield after adjustments for age and season of calving. Herd-year means and standard deviations were determined using aLl cows in a herd-year including those with unknown sires. Average herd-year mean and SD were less for Colombia and Puerto Rico than for Mexico. Average herd-year SD within same herd-year mean classification also were smaller for Colombia and Puerto Rico compared to Mexico. Coefficients for daughter milk response regressed on sire PD were similar in Colombia (.31 f -02) and Puerto Rico (.32 f .02) and greater in Mexico (.54 f .02). Daughter responses increased similarly and approximately linearly with increasing herd-year SD in each country but not with increasing herd-year mean. Daughter milk response to sire selection was less than reported responses in US herds with similar herd-year means and SD. Therefore, using sire PTA estimated from US daughters wiU overestimate milk