Methods to Reduce Feeding Time Aggression Studied

When feeding horses in groups, increasing their distance apart and time spent eating might help reduce aggression, Swiss researchers say.

Wild horses are rarely aggressive during feeding because of the vast open areas and lengthy feeding times, but domestic horses often live in confined spaces with brief feeding times, said Anic Ostertag, MSc, ETH Biology, of the Animal Behaviour, Health, and Welfare Unit of the Institute of Agricultural Sciences at the Swiss Federal Institute of Technology, in Zurich. Ostertag presented her study results at the 2014 Swiss Equine Research Day, held April 10 in Avenches.

In their recent study Ostertag and her colleagues found that caretakers can limit aggression during feeding time by separating the horses by distance or barriers and by lengthening the feeding time with hay nets, for example, she said. This finding complements work by Dutch scientists, who found that frequent feeding can help keep aggressive activity low.

The Swiss group studied 390 horses in 50 different domestic housing groups, which included between four and 21 adult horses each. Each housing situation was equipped with one of six different kinds of group feeding systems:

  • Lump ground feeding;
  • A hay rack;
  • A feed fence (hay racks with separating bars between horses’ necks);
  • Slow-feed hay nets;
  • Open feeding stalls (with or without contact in the head area); and
  • A combination of several of these systems.

Researchers observed the horses for 30 minutes prior to feeding as well as the first 30 minutes of feeding. They recorded any aggressive behaviors—such as approaching, pushing, threatening behavior (e.g., bite threat, kick threat), biting, kicking, attacking, and chasing—the horses exhibited. The team also interviewed the stable managers.

(Images left to right: The hay rack, the feed fence, feeding stalls with contact, and feeding stalls without contact. Photos: Courtesy Joan-Bryce Burla)

Overall, most aggressive behaviors (64%) were noncontact threats, Ostertag said. But there were significant differences in aggression among the different feeding systems. The team observed the fewest aggressive behaviors in systems where the hay was spaced far apart (at least 1 to 1.5 meters) for each horse or where horses were separated by a physical barrier, even if the barrier still allowed horses to move freely in and out, she said. They saw the highest incidence of aggression in lump feeding on the ground, where all the horses had the same common access to the same single resource.

Aggression was also significantly reduced when feeding took a longer amount of time, Ostertag said. This was true when horses had to pull hay from slow-distribution feeders or hay nets.

“Based on the results of this study, it is recommended that horses in group housing have constant access to straw and hay, and to divide feeding sites by sufficient distance or partitions,” Ostertag said. “Since constant feeding is often problematic, however, caretakers must manage food intake by reducing the consumption rate, for example, with feeding nets to make feeding times last as long as possible. This allows a feeding behavior that is similar to natural conditions, helping prevent not only behavioral disorders but issues of the digestive tract as well.

“These two aspects—separation and prolonged feeding—should be taken into account in the feeding management of horses kept in groups,” she said.