Behavioural and physiological effects of virginiamycin in the diets of horses with stereotypies.

This research article explores the potential impact of virginiamycin, an antibiotic and feed additive, on the behavior and physiology of horses. The study finds that, while the supplement doesn’t alter the animals’ stereotypic behaviors, it does influence their exploration tendencies, water consumption, and potentially their feeding motivation.

Objective and Methodology

• The research focused on examining the potential effects of dietary supplements of virginiamycin, a microbial-derived antibiotic commonly used as a feed additive, on the behavior and physiological responses of thoroughbred gelding horses.
• The experiment consisted of a control group and two groups of horses exhibiting specific stereotypic behaviors – cribbers (horses that compulsively bite or chew wooden objects) and weavers (horses that sway side to side repetitively). In total, 17 horses were studied.
• The comparison was carried out over a duration of 16 weeks, where the horses’ behaviors and physiological impacts were recorded and analyzed between placebo and virginiamycin supplement diets.

Findings on Stereotypic Behaviour

• The results showed that the addition of virginiamycin to horse diets did not lead to any noticeable changes in their stereotypic behavior, i.e., it neither reduced nor increased any compulsive chewing or swaying habits seen in cribbers and weavers respectively.

Impact on Explorative Behaviour

• The study noted that virginiamycin affected the explorative behaviors of the horses. Specifically, it was seen to reduce such behavior, which the researchers speculate could be due to a decrease in feeding motivation encouraged by the supplement.

Effect on Water Intake

• In terms of physiological impacts, the study observed changes in water intake among the horses. Cribbers who were kept on a diet supplemented with virginiamycin consumed more water, whereas there was a decrease in water intake in the control group of horses.
• However, the researchers noted that they could not definitively attribute these changes to the supplement due to potential confounding factors which were not identified or controlled in the study.

Other Observations

• Regarding overall behavior and physiological changes, virginiamycin did not lead to any other significant impacts on the horses’ health or habits.
• The study also confirms that the addition of virginiamycin had no observable effect on the digestibility of the horses’ food, indicating that it did not interfere with their digestive systems or appetite significantly.