Effectiveness of Genomic Testing in Predicting Carcass Characteristics and Feedlot Performance

Three hundred and forty crossbred steers were utilized in a two-year study (n = 160, Year 1; n = 180, Year 2) to examine the effectiveness of commercially available genomic testing for predicting carcass characteristics and feedlot performance. Steers in Year 1 were consigned by 8 producers (average entry weight 307 ± 41.4 kg) and in Year 2 by 16 producers (average entry weight 292 ± 38.9 kg) as part of a retained ownership demonstration program. In both years steers were fed in a single pen and fed a common diet with a final energy concentration of 1.36 Mcal NE_g/kg. Hair samples for DNA analysis were collected at time of implanting and submitted to be analyzed using two different non-breed specific DNA panels. The PredicGen (PG; Zoetis, Inc., Parsippany-Troy Hills, NJ) test was used in Years 1 and 2 while Igenity Silver (IGS; Neogen, Lansing, MI) was used in Year 1 and Igenity Gold was used in Year 2 (IGG; Neogen, Lansing, MI). Traits evaluated by the PG test were marbling score (PG-Marb), USDA Yield Grade (PG-YG), and Grid Value (PG-GV). Traits evaluated by the IGS test were marbling score (IG-Marb) and ADG (IG-ADG). In addition to IG-Marb and IG-ADG, IGG estimates for fat thickness (IGG-FT) and LM area (IGG-LMA) were added in Year 2. Steers were harvested in three groups at d176, d212, and d240 in Year 1 and d182, d203, and d224 in Year 2 with a target carcass fat thickness of 1.27 cm. Hot carcass weights were recorded on the day of harvest with carcass 12^th-rib fat thickness (FT), LM area (LMA), USDA marbling scores and Yield Grades (YG) collected following a 24-h chill. Average daily gain was calculated using initial weights shrunk four percent and HCW divided by 62%. Grid values were derived using the same premiums and discounts across Year 1 and Year 2. Carcass marbling scores were positively correlated with PG-Marb and IG-Marb (0.405, P < 0.001 and 0.493, P < 0.001), respectively. The IGG test was positively correlated with FT and LMA (0.525, P < 0.001 and 0.368, P < 0.001, respectively). The USDA YG was negatively correlated with PG-YG (-0.493, P < 0.001). Average daily gain was correlated with IG-ADG (0.227, P < 0.001) and Grid Value was correlated with PG-GV (0.133, P = 0.016). The PG, IGS, and IGG genomic test results were correlated with actual carcass characteristics of crossbred steers.