The effect of feeding order of forage and oats on metabolic and digestive responses related to gastric emptying in horses.

This research article studies how the sequence of feeding horses—whether oats are given first then hay, or the reverse—affects the process of digestion, particularly gastric emptying, and results in metabolic changes.

Study Design and Procedure

• The researchers used a 2×2 crossover design to conduct this study on four caecum-cannulated horses, thereby allowing each horse to be evaluated under both feeding conditions. The design spanned two 12-day periods, comprising 10 days for transitioning the horses to the different feeding orders and 2 days to collect data.
• The hay was given to horses at three fixed daily times, while the oats were fed 15 minutes before or 1 hour after serving hay, depending on the allocated feeding order. Data was gathered by researchers up to eight hours following feeding.
• To determine the rate of gastric emptying, the 13C acetic acid breath test was applied. This involved mixing 13C acetic acid with the oats and later analyzing the breath samples for the ratio of 12C:13C. As the 13C is expelled via the breath, this gives an estimate of how quickly the oats are being digested and cleared from the stomach.
• Metrics such as the gastric emptying coefficient (GEC), the time taken for half of the 13C to be expelled (t1/2), and the Tmax – the period at which maximum 13C expulsion occurred – were calculated.
• The researchers also gathered hourly blood and caecal fluid samples. The blood plasma was analyzed to decide the levels of glucose and insulin, baselines, peak concentrations, timings of peaks, and the areas under the curves (AUCs).
• A pH probe was positioned in the caecum for pH measurements taken every minute to establish the minimum pH and the time needed to attain this minimum pH. The pH and short-chained fatty acid (SCFA) concentrations of caecal samples gathered hourly were also analyzed.

Key Findings

• The research demonstrated that the feeding sequence significantly affects the gastric emptying in horses – Tmax was longer when hay was fed before oats compared to the reverse order. This suggests that the digestion process was slower in the former case. However, no effect was observed on GEC and t1/2.
• No consequential variation was detected in plasma glucose and insulin as a result of the feeding sequence.
• While the minimum pH did not vary with the feeding sequence, the time taken to reach it did. When hay was fed before oats, it took longer to reach minimum pH, and the average pH was lower in the stipulated intervals.
• SCFA concentrations were found to be more affected by time of sampling rather than the feeding sequence.
• The study conclusively demonstrated that feeding order influences gastric emptying and digestion, effects that are more evident in the caecal pH than the plasma glucose and insulin levels.