Effects of crude protein intake from grass silage-only diets on the equine colon ecosystem after an abrupt feed change.

This research study focuses on the impact of dietary protein intake on the colon health of horses. Specifically, the researchers explored the influence of two diets that differed in protein concentration on the bacterial balance in the horse’s colon ecosystem, especially after a sudden change in diet.

Objective and Methodology of the Study

• The study’s main goal was to assess the effects of crude protein (CP) intake from two distinct grass silage-only diets on the health of the equine colon. The diets differed in their CP concentration but were fed at similar dry matter intake (DMI).
• Four adult horses with a right ventral colon-fistula were included in the study. These horses were fed a high-protein diet (HP, 873g of CP per day), and a diet providing the recommended protein intake (RP, 615g of CP per day).
• Each diet was fed for an adaptation period of 15 days, followed by two experimental periods where the diets were fed for 22 days each in a crossover design.
• To monitor the effects of the dietary change on the colon, samples were collected at specific intervals: before changing the diet, 4, 12, and 24 hours after the change, and on the 7th, 14th, and 22nd day following the change.

Results of the Study

• The concentrations of total anaerobic bacteria and lactobacilli were higher in the horses fed the HP diet as compared to the RP diet during the first 24 hours after the feed change.
• No notable differences were observed in volatile fatty acid (VFA) concentrations between the HP and RP diets during the first 24 hours post feed change.
• However, between day 7 and day 22, total VFA concentrations were higher in the horses fed the HP diet as compared to the RP diet. Additionally, the colon pH of the horses was lower with the HP diet than with the RP diet.
• There were no significant differences in nitrogen, ammonia, urea concentrations, and osmolality of the colon fluid between the HP and RP diets after an adaptation period of 22 days.
• The study did not find any noticeable changes in fecal pH and colon and fecal dry matter (DM) throughout the experiment.

Conclusions of the Study

• The results demonstrate that feed changes between silages with different CP content could alter the colon bacterial counts within the first 24 hours in horses.
• Moreover, over the following three weeks, there was a slight decrease in pH and an increase in VFA concentrations. However, no other major changes occurred in the composition and activities of the colon ecosystem or fecal DM.
• This suggests that while a change in diet can affect certain aspects of colon health in the short term, these changes may not have a lasting significant impact over the longer term.