Genetic effects for reproductive performance of straightbred and crossbred Romosinuano and Angus cows in a temperate zone

The objectives of this work were to: (1) estimate heterosis and breed direct effects for cow reproduction traits of Romosinuano, Angus, and F 1 cows in a temperate climate, and (2) assess the effects of the type of forage grazed (bermudagrass, endophyte-infected and endophyte-free tall fescue) during the breeding season on traits and genetic effects. Calving and weaning rate ( n =666 records) were evaluated for 145 cows from 2005 through 2012. Calving interval ( n =400) and day of conception within breeding season ( n =547) were recorded. Mixed models included combinations of fixed effects: year of record or cow age within year of record, breed type parameterized as main and interaction effects of sire breed and dam breed of cows with records. Additive genetic effects were included as a random component. The sire breed-dam breed interaction was characterized by lower ( P 1 ) for calving rate and ranged from 0.81±0.03 (F 1 sired by Angus) to 0.82±0.03 (Romosinuano-sired F 1 ) for weaning rate. Romosinuano cows conceived later ( P P P >0.24). Estimates of heterosis were 0.09±0.03, 0.11±0.04, and –3.7±2.0 d ( P P P