A new study from Brazil suggests that managing a mare’s environment to reduce her stress levels after she has been bred can increase the likelihood of a successful pregnancy.

Researchers at Universidade Federal do Rio Grande do Sul in Porto Alegre studied the breeding records of 1,206 Thoroughbred mares over the course of 10 breeding seasons. Based on how they were managed immediately after they were bred, the mares were divided into two groups: those who were managed in a manner intended to reduce social stresses—such as minimizing or eliminating stall confinement and maintaining herd stability—and those who were not.

A review of the foaling rates of the two groups showed that social stress sometimes seemed to influence whether pregnancy was carried to term. When mares that had not produced a foal the previous year—known as “barren”—were managed to reduce social stress, their pregnancy rate was 7 percent higher than that of barren mares who received no special management. In all, the “low stress” group of barren mares had a pregnancy rate of 91.8 percent, while 84.7 percent of the barren mares in the other group had successful pregnancies.

The researchers conclude that taking steps to reduce social stress in mares immediately following breeding can result in increased foaling rates.

Reference: “Management strategies aiming to improve horse welfare reduce embryonic death rates in mares,” Reproduction in Domestic Animals, May 2015

This article first appeared in EQUUS issue #455, August 2015.