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Managing Stress for Reproductive Success

Less-excitable cows show $60-per-year advantage to excitable herdmates.

RUIDOSO, NEW MEXICO (Aug. 29, 2018) — Stress experienced by beef cattle can affect performance, including reproduction. Temperament, or behavioral response to stimuli, is a stress factor with physiological and genetic effects that is being studied by animal scientists.

Compared to “excitable” cows, “adequate” cows have higher pregnancy rates, calving rates and weaning rates, reported Cliff Lamb, Texas A&M University.

During the Applied Reproductive Strategies in Beef Cattle Workshop hosted Aug. 29-30 in Ruidoso, Texas A&M University (TAMU) animal scientist Cliff Lamb discussed the implications of temperament. He shared information based largely on research conducted by fellow TAMU researcher Reinaldo Cooke.

Lamb explained how temperament was assessed, based on how animals reacted under restraint (chute score) or the speed with which they left restraint (exit velocity score). Typically, these measurements are combined into a single value or temperament score, ranging from 1 (docile) to 5 (aggressive).

“Animals with a score of 3 or less are considered ‘adequate’ for temperament, while animals with scores over 3 are considered ‘excitable,’” said Lamb.

Since temperament is at least a moderately heritable trait, change can be made in response to genetic selection. Lamb suggested that temperament scores can be in sire selection and for culling overly temperamental females. He allowed, however, that “some” temperament should probably be maintained in cow-calf systems so that cows are protective of calves. In the feedlot, it is desirable for animals to have the gumption necessary to compete for bunk space.

Focusing on how temperament can affect reproduction, Lamb said evidence shows higher temperament scores among heifers are associated with later age at puberty. Higher temperament scores also correlate with higher blood cortisol concentration in response to stress. Cortisol can inhibit hormone action, thus interfering with the estrous cycle.

Compared to “excitable” cows, “adequate” cows have higher pregnancy rates, calving rates and weaning rates, reported Lamb.

“There is an economic impact. These cows return more dollars to the operation than excitable cows — about $60 per cow per year more,” said Lamb, noting that the return may be greater if you consider that excitable animals incite stress among herdmates, thus hindering their performance, too.

Another method of managing for improved temperament is through acclimation. Lamb shared results of research showing how planned acclimation of weaned heifers, through repeated exposure to human handling and common handling procedures, resulted in lowered cortisol concentrations. Compared to control groups, acclimated heifers also reached puberty earlier and more became pregnant early in the breeding season. This was true of heifers with Bos indicus influence, as well as Bos taurus heifers. However, studies showed no significant effects of acclimation for mature cows. It works best for young animals.

For details on Lamb's presentation — including the proceedings, PowerPoint and video of his presentation — visit the Newsroom at www.appliedreprostrategies.com.

Editor's Note: This article was written under contract or by staff of Angus Media. To request reprint permission and guidelines, contact the Angus Media editorial team at 816-383-5200.