Live weights at fixed ages of Dairy Shorthorn, Red Friesian, Red Holstein, Meuse-Rhine-Yssel, Simmental and other sire breed progeny of Dairy Shorthorn, Red Friesian and crossbred dams, and estimates of heterosis and apparent heritability

Abstract

ABSTRACTDairy Shorthorn (DS), Red Friesian (RF), Red Holstein (RH), Danish Red (DR), Meuse-Rhine-Yssel (MR), Simmental (SM), British beef breeds (BB) and hybrid (HY, RF♂ × DS9 and RH♀ × DS?) bulls were progeny tested on DS, RF and HY cows as part of a breed improvement project. Live-weight records for 4 450 animals in 17 herds by 350 sires were used to calculate adjusted hundred-day weights from 100 to 700 days of age. Genotype × environment interactions were significant (P < 0·001) and data for two production systems (cereals and grass) were analysed separately. RF, RH, DR and MR progeny were, proportionally, 0·10 to 012 heavier than DS (P < 0·001). On cereals the SM were significantly heavier than these crosses (0·095, P < 0·001 at 400 days) but not on grass. BB and HY were generally not significantly different from DS. Only DS dams were represented on cereal systems. On grass, breed differences were similar for different dam breeds but estimates of hybrid vigour averaged 0·051 in RF♂ × DS♀, 0·061 in RF♂ × (RF♂ × DS♀)♀ and were not significantly different from zero in DS♂ × (RF♂ × DS♀)♀. Apparent heritability averaged 0·50 ± 0·12 but was lower during a period of feed restriction. The within-breed genetic correlation for live weight on the two systems of production was unity.