Associations of cardiovascular function and structure with feed efficiency in beef cattle
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Heart rate as a feed efficiency proxy could aid in the reduction of beef cattle feed costs. Applicable heart rate assessments remain to be developed and the basis of the association between heart rate and feed efficiency evaluated, before heart rate proxies are implemented. Study 1 assessed associations of overnight and acute stress heart rate with feed efficiency in heifer calves and yearling heifers. Study 2 evaluated relationships of cardiovascular function and structure measures with feed efficiency in bulls, steers and heifers. Efficient heifer calves displayed lower overnight heart rates and higher heart rate responses to acute stress, no difference in heart rate was observed in yearling heifers. Cardiovascular function and structure measures were associated with feed efficiency; with structure measures (i.e. ventricle thickness) indicating reduced cardiovascular workload. Heart rate through associations with other cardiovascular measures and metabolism has potential as an applicable proxy for beef cattle feed efficiency improvement.