Livestock Production Estimated Additive and Non - additive Breed Effects and Genetic Parameters for Ultrasound Scanned Traits of a Multi - breed Beef Population in Tropical Australia

Direct additive, dominance and genetic parameters for ultrasound scan traits of a multi-breed population involving European, British, Sanga and Brahman breed types were estimated. A generalized ridge regression technique was used to eliminate high associations among some of the genetic effects in the model. Clear breed type effects were observed for all scanned traits. European breeds had negative and positive direct additive genetic effects for fat and eye muscle area, respectively in both heifers and bulls. British, Sanga and Brahman had positive direct additive effects for scan traits in heifers and bulls. Estimated heterosis of Brahman crosses were higher than non Brahman crosses for fat traits and ranged from 2% to 13%. The estimated heritabilities for rump fat, rib fat and eye muscle area of heifers were 0.36, 0.34 and 0.36 and for bulls 0.33, 0.23 and 0.39, respectively.