Effects of Internal Parasite Infection at Feedlot Arrival on Performance and Carcass Characteristics in Beef Steers

The performance and carcass characteristics of 43 beef steers were evaluated relative to internal parasite burden at feedlot arrival. Despite being effectively dewormed at feedlot entry, cattle with more significant worm burdens on arrival had lesser body weights throughout the feeding period and tended to have more days on feed. Even with a tendency for more days on feed, more heavily infected cattle also tended to have lesser marbling scores, dressing percentages, KPH, and back fat. However, there were no differences in ADG throughout the finishing period, REA, yield grade, or HCW relative to initial worm burden. These data indicate that larger worm burdens at feedlot arrival can have long-term effects on body weight and carcass characteristics even when deworming procedures are successful. This information highlights the importance of internal parasite control during the grazing and growing period.