PSII-8 - Analysis of maternal influence on Phenotypic Ultrasound Measurements of weaned Angus calves

Abstract: Ultrasound carcass data can be used to accurately estimate the body composition of beef cattle in comparison to a body composition score. Literature regarding the analysis of phenotypic carcass data has focused predominately on yearling or mature cattle with limited measurements on weaned calves. Therefore, the influence of the dam’s milking ability on body composition traits measured via carcass ultrasound is unknown. The objective of this study was to estimate correlations between the maternal influence of the dam on the phenotypic ultrasound measurements of the calf. To quantify maternal influence, the dam’s expected progeny difference (EPD) for milk (MILK) was correlated to three ultrasound measurements of the calf: backfat thickness (BFAT), ribeye area (REA), and intramuscular fat (IMF). Ultrasound measurements were collected one week after weaning on 104 purebred Angus heifer calves from the Iowa State University McNay Memorial Research and Demonstration Farm located outside Chariton, Iowa. The average age and weight for heifers were 187 days and 195 kg, respectively. The dam’s milk EPD was correlated to the ultrasound measurements taken on the calves. For each trait, Pearson’s correlations were calculated between the calf’s ultrasound traits to the dam’s milk EPD using R Statistical Software version 4.3.1. A small positive correlation was identified between MILK and REA (r = 0.28, P = 0.004). This suggests a weak phenotypic relationship between MILK and REA for weaned heifers. The correlation between MILK to BFAT and IMF was 0.10 (P = 0.318) and -0.05 (P = 0.619), respectively. These correlations were not significantly different from zero. This suggests the dam’s potential for milk production has little association with BFAT and IMF for weaned heifers. Although further research is needed, the results from this study indicate little to no relationship between dam’s milk EPD on the calf’s ultrasound measures for BFAT, REA, and IMF.