Interpretive Summary: Cattle breed type and anabolic implants impact calpastatin expression and abundance of mRNA associated with protein turnover in the longissimus thoracis of feedlot steers

By: Caleb C Reichhardt, Chandler D Stafford, Jocelyn M Cuthbert, David S Dang, Laura A Motsinger, Mackenzie J Taylor, Reganne K Briggs, Tevan J Brady, Aaron J Thomas, Matthew D Garcia, Sulaiman K Matarneh, Kara J Thornton

Two methods that the beef cattle industry can use to potentially improve efficiency, sustainability, and economic viability are growth promotants and crossbreeding cattle of different breed types. In the United States, over 90% of cattle receive at least one anabolic implant during the production cycle resulting in improvements in production and overall economic and environmental sustainability. Research suggests that the two main cattle breed types, Bos indicus and Bos taurus, respond differently to different anabolic implant strategies. The objective of this study was to characterize changes that occur in the skeletal muscle following implanting in Bos indicus influenced animals and Bos taurus animals. This research measured mRNA abundance of 24 genes associated with skeletal muscle growth, and protein expression of calpain-1 and calpastatin. The findings of this research suggest that anabolic implants and cattle breed type interact to cause changes in mRNA abundance in the longissimus thoracis that are related to protein turnover of skeletal muscle. Furthermore, calpastatin protein abundance was also altered by this breed × treatment interaction. This research demonstrates that anabolic implants cause molecular changes in skeletal muscle of feedlot steers, with some of these changes being breed dependent.