Experience tells most producers that high strung, poorly tempered stock, sometimes do not perform as well as herd mates with a more moderate disposition. Science has backed this up in the feedlot with studies showing steers with calmer dispositions out gaining steers with the most excitable temperaments. Links are also being made by research between disposition and health, including response to vaccination. Most of all, stock with a bad temperament pose a greater risk to you being injuring during handling.
Determining if a link exits between reproductive performance and disposition has been difficult to prove. Anecdotally, producers and A.I. technicians have noted that cows with bad temperaments are less likely to conceive to A.I. However, putting hard numbers to this has proven difficult.
In an experiment at Oregon State University by Reinaldo Cooke, crossbred heifers were divided into two groups. After weaning one group was trained for handling by being brought up from pasture to a pen three times a week, for four weeks, so that they’d become acclimated to people and going through a working chute. The other group was not handled during this time and was left on pasture. Both groups were tested for the hormone Cortisol. This hormone is associated with stress and is part of the “fight or flight” response in animals. When Cortisol levels are elevated, it is an indicator of stress. Some research indicates elevated cortisol levels impair the naturally occurring reproductive hormones LH and FSH, and could help explain why stressed or poorly tempered animals may have poorer fertility.
Since these were young heifers not ready to breed yet, you might be asking what could possibly be proven by this experiment. The results of this study found two important differences in the trained group that could impact reproduction down the road. First, the group that was handled had lower Cortisol levels at the end of the four week training period than the non-trained group. Secondly, the trained group reached puberty at a faster rate than the non-trained heifers, with nearly a 20% difference in the number of heifers cycling five, six, and seven months after the project began. Having these heifers start cycling sooner can greatly improve reproduction by allowing heifers to be bred sooner and calve early in the calving season. These heifers will ultimately have more time to recover before breeding again as first calf heifers, and have a greater opportunity to maintain an early caving interval throughout their lives.