|dc.description.abstract||Cattle breed associations have realized the usefulness of real time ultrasound (RTU) measures of body composition from yearling bulls and heifers in combination with live weights to conduct national cattle genetic evaluations for carcass merit. The data collected in these evaluations are used to adjust carcass data collected on the progeny of sires. Including live animal data allows evaluation of a larger, more random sample of the population while increasing the accuracy with which replacements are evaluated. Research has reported genetic parameter estimates among live animal measurements of yearling replacements and carcass traits of market progeny in the Simmental breed.
The objective of this study is to determine how accurately sire expected progeny differences (EPDs), ultrasound data and progeny carcass data are at predicting phenotype of offspring, and the level of selection at which the most rapid genetic advancements be made. Bull’s EPD percentile ranks for intramuscular fat (IMF), longissimimus muscle area (LMA) and rib fat (RF) were compared against a sire’s progeny’s ultrasound or carcass measurements. Number of sires included 1376 Gelbvieh, 78 Red Angus and 287 Angus bulls. Comparing Angus sire IMF rank to progeny ultrasound IMF scores was significant in yr 01 (P < 0.05). Gelbvieh group sire EPD ranked IMF were compared to progeny carcass IMF (CIMF). Sire IMF rank correlated to progeny CIMF scores in yrs 89, 90, 94, 95 96, 98, 99, 00, and 01 (P < 0.05). Gelbvieh sire LMA rank compared to progeny carcass LMA correlated in yrs 94, 96, and 98 (P < 0.05). Angus sire RF rank correlated to progeny ultrasound RF (URF) in yrs 99 and 00 (P < 0.05). Comparing Red Angus sire RF rank to progeny URF in cm was significant in yrs 02 and 03 (P < 0.05). Comparing Gelbvieh sire RF rank to progeny URF in cm was significant in yrs 99 and 01 (P < 0.05). Comparing Gelbvieh sire RF rank to progeny carcass RF in cm was significant in yrs 82, 92, 95, 96, and 02 (P < 0.05). However, results did not yield findings to allow producers to make mating selections at a specific selection pressure and more research should be conducted to determine at what level of selection the most rapid genetic improvement will be made.||