Beef Cow Production Efficiency and The Interaction of Level of Intake and Genotype

Mature Angus x Hereford (Ax; n=25), Simmental x Hereford (Sx; n=21), and Tarentaise x Hereford (Tx; n=22) cows from 1 year of a multi-year study were used to determine if an interaction exists between level of intake (LOI), expressed as metabolizable energy intake (MEI), and genotype for production efficiency [PE=g calf weaning weight/(11-month cow+ calf MEI) and PE=Mcal milk energy/(11-month cow MEI)]. A subsample of Ax (n=l5) and Sx (n=l6) cows from 2 years of this study were also used to evaluate treatment effects on energy partitioning by conventional balance techniques and respiration calorimetry. Cows were managed in drylot where individual feed intakes of cows and calves were measured for 11 months through weaning after 1 month adaptation to LOI treatments. Results indicate cows on low intake (L) were 6% more efficient for weaned calf weight production than cows on moderate intake (M; P.75), as expected, were affected by LOI (