The evaluation of seven microsatellite markers and real time ultrasound information as tools for selecting animals for improved carcass characteristics and beef tenderness

This study evaluated seven published bovine microsatellite markers selected from the USDA-MARC database for their usefulness as a selection tool for beef tenderness. Data from steers from ten different sire breeds were sorted into the top (upper tail, n = 25) and bottom (lower tall, n = 25) steers for average daily gain, marbling score, rib eye area, and Warner-Bratzler shear force (WBS) following a 14 d aging treatment. The resulting 200 animals were genotyped by a commercial laboratory (Celera AgGen, Davis, CA) for microsatellite markers BMC1501 (Leptin), BMC9001 (Nebulin), BMS 1678 (Thyroglobulin), BY5 (Myostatin), URB011 (Calpain), CAST (Calpastatin), and BM2394 (WBS). For all but one marker, additional alleles were discovered in the study. Additionally, analysis revealed that several markers had significant effects on some carcass and tenderness traits. These results imply that it may be possible to select for unique alleles to help Improve beef tenderness.

Moreover, the study analyzed the Impact of growth Implants, sire breed and sire on carcass value and profitability. Implanted animals showed an increased carcass value of over $40 per head over non-Implanted animals. There was a range of sire EPD's for carcass value of $67 (-$37 to $30) from all sires in the study, indicating that sire selection can be a very important aspect of profitability in a retained ownership program. The decision to retain ownership is often a financial risk, therefore it is important to consider all management options that have a potential to maximize profit. Realized profit from retaining ownership was higher for animals implanted (P < 0.05). Non-implanted animals had a negative LS means for realized profit (-$27 per animal), while both SS and SR implant treatments had positive realized profit ($32 and $15 per head, respectively).

The study also evaluated a new real time ultrasound software package to determine accuracy of prediction of carcass traits and tenderness. Pearson correlation coefficients between carcass fat thickness and ultrasound fat thickness was highly correlated (r = 0.81). Similarly, Spearman's correlation coefficient was also highly correlated for ultrasound fat thickness and carcass fat thickness (r = 0.84). Analysis of variance results indicated that ultrasound fat thickness measurements accounted for a significant amount of carcass fat thickness variation (R^= 0.65, P< 0.0001). Pearson correlation coefficients between average percent chemical fat and marbling score with ultrasound percent intramuscular fat was 0.519 and 0.600, respectively. Pearson correlation coefficient between the carcass ribeye area and ultrasound ribeye area was insignificant at 0.063 (P = 0.6132) as was the Spearman's correlation coefficient (r = 0.086; P = 0.4938). Analysis of variance between ultrasound ribeye area revealed that it failed to account for a significant amount of variation in carcass ribeye measurements (R^ = 0.004, P = 0.613). Results indicated that the software does not accurately predict ribeye area. The unique aspect of the software utilized in the study is the ability to predict tendemess. However, the data revealed an Insignificant correlation between ultrasound tenderness score and WBS or any sensory panel tenderness ratings. Additionally, analysis of variance failed to detect an association between ultrasound tenderness scores and WBS and sensory panel scores.