Energy utilization by Hereford and Simmental males and females

Abstract

Post-weaning metabolizable energy intake, growth of empty-body chemical components and efficiencies of energy utilization were evaluated for Hereford intact males (17) and females (16) and Simmental intact males (15) and females (16) during a 212-day feeding period. Within each breed × sex subclass, animals were assigned to one of three levels of metabolizable energy (ME) intake: (1) 544 kJ/kg M^0·75 per day, (2) 795 kJ/kg M^0·75 per day, and (3) ad libitum. Body composition of each animal was estimated at the beginning and end of the feeding period by deuterium oxide dilution.Protein and water gain of Hereford and Simmental cattle were similar at restricted levels of intake but were greater for Simmental than for Hereford cattle at ad libitum intakes. Similarly, rates of protein and water gain tended to increase more rapidly in response to increased energy intake by males than by females. Hereford males gained fat and energy slightly more rapidly than Hereford females, but Simmental males gained fat and energy at slower rates than Simmental females.Males had higher maintenance requirements and tended to use ME with less efficiency for maintenance and gain than females. Hereford cattle had lower maintenance requirements and used ME with greater efficiency for both maintenance and gain than Simmental cattle.