Intake estimation of horses grazing tall fescue (Lolium arundinaceum) or fed tall fescue hay.

This research investigates how much of tall fescue, either as hay or fresh grass, horses would consume, using alkane markers as a form of estimation. The conclusion suggests that horses have a higher intake of tall fescue when it is offered as pasture in comparison to hay.

Study Design and Methodology

• The study was set up using six mature geldings of light horse breeds. These horses were randomly assigned to two groups of three. One group was given nontoxic endophyte-infected tall fescue hay, while the other was allowed to graze on tall fescue pasture.
• The study used a crossover design across 14-day periods. During the pasture period, horses were kept in stalls from 0700 to 1300 h each day with access to water. They were then allowed to graze together in a single 0.4 ha pasture from 1300 to 0700 h. During the hay period, horses were kept alone in stalls and allowed free access to hay from 1300 to 0700 h.
• All horses were also separately given 225 g of oats twice each day. These oats were treated with hexatriacontane (C36), an external marker.
• Fecal samples were collected at 0700 and 1900 h from day 10 to 14 of each period. These samples were analysed for two more alkanes, tritriacontane (C33) and hentriacontane (C31), which were used as internal markers.

Findings and Conclusion

• Using either C33 or C31 as internal markers, the estimation of hay dry matter intake (DMI) did not significantly differ from the measured hay DMI.
• Pasture DMI was observed to be greater than hay DMI. Dry matter digestibility (DMD), or how effectively the horses could utilize the food, was also higher for pasture compared to hay. These results are significant, suggesting that horses may prefer, and better digest, fresh tall fescue over hay.
• The results also suggested that alkanes can be useful markers for estimating pasture or hay DMI and DMD in future research. This methodology could be helpful in equine nutrition studies and for horse owners to understand feeding behaviours.