050 Endophyte-Infected Tall Fescue Seeds Had No Effect on Carcass Characteristics of Beef Cattle

Abstract The objective of this study was to investigate the effects of feeding endophyte-infected tall fescue seeds on carcass characteristics including dressing percentage, ribeye area, backfat thickness, percentage of KPH fat, pH, objective lean color, marbling score, and intramuscular fat content. Twelve Angus steers of the same preconditioning operation entering the stocker phase at Mississippi State University H. H. Leveck Animal Research Center were selected and blocked by BW into 3 groups: light (4 animals, 205.5 ± 7.4 kg), medium (5 animals, 231.3 ± 8.2 kg), and heavy (3 animals, 272.7 ± 8.4 kg). A control (KY32 or E–; 0.9 kg) and a treatment (KY31 or E+; 0.8, 0.9, or 1.0 kg for light, medium, or heavy steers, respectively, to provide 20 µg of ergovaline per kg of BW) were randomly assigned to animals within blocks (n = 6) by using Calan® gates. Seeds were mixed with soybean, corn gluten pellets at 2% of BW in the Calan® gates during two trials of 70 d (Summer 2015) and 56 d (Winter 2016). Upon the completion of the second trial, steers were implanted with one dose of Ralgro® and finished to a slaughter weight of approximately 499 kg. During the entire study, steers had ad libitum access to the same annual and perennial summer grass pasture, alfalfa hay supplementation, minerals, and water. Hot carcass weight and dressing percentage were recorded at slaughter, whereas all other data were collected at 72 h post mortem on the right side of the carcasses. Statistical analysis was performed by the GLIMMIX procedure of SAS with significance level of 0.05. There was no difference in carcass characteristics between the E- and E+ treatments (P > 0.199). Carcasses from steers fed KY31 and KY32 seeds had dressing percentage of 48.7 to 49.8%, ribeye area of 62.9 to 64.4 cm2, backfat thickness of 0.41 to 0.46 cm, KPH fat of 1.2 to 1.3%, lean pH of 5.6 to 5.7, L* value of 39.35 to 39.75, a* value of 35.43 to 36.04, b* value of 31.75 to 32.74, and a marbling score of 226.7 to 236.7. Ultrasound prediction of steers before slaughter indicated an intramuscular fat content of 4.1 to 4.2%, agreeing with marbling score evaluation. Results suggested that ingestion of endophyte-infected tall fescue seeds followed by a withdrawal period might not have residual effects on carcass characteristics of grass-finished beef cattle.