Direct, Maternal and Heterotic Effects for Production Traits of a Two Breed Diallel Between Holstein and Brown Swiss Under Subtropical Conditions

Abstract The present study aimed to estimate direct, maternal and heterotic effects for production traits of a two-breed diallel between Holstein and Brown Swiss under subtropical conditions. The study was carried out with information collected at the Las Margaritas experimental site, belonging to the National Institute of Forestry, Agriculture, and Livestock Research. Productive and genealogical information from cows belonging to the genetic groups Holstein (HO; 64), Brown Swiss (BS; 91), and their F 1 reciprocal crosses HO/BS (29) and BS/HO (25) were used. The analyzed traits were: total milk yield per lactation (TMY, kg), lactation length (LL), milk yield per day (DMY; kg/d), milk yield per calving interval (IMY), and cow weight at calving (CW; kg). The MIXED procedure was used for data analysis. Models included the fixed effects of sire breed, dam breed, calving year, calving season, parity number and the interaction between sire breed and dam breed, except for the IMY analysis, which did not include the parity number. Contrasts were used to estimate individual heterosis and differences in direct and maternal genetic effects. The sire breed effect was only significant for LL (p < 0.05), while calving year was significant for TMY and IMY. Both calving season and parity number were significant for TMY, DMY, and CW. The sire breed * dam breed was significant for TMY, DMY and IMY. Heterosis was significant for TMY, DMY and IMY with values of 422.92 kg, 1.38 kg/d, and 1.48 kg/d, respectively. Direct and maternal genetic effects were only significant for LL.