Revelations About Ponies and PasturesBy Dr. Kathleen Crandell · July 29, 2011
At the recent Equine Science Society meeting, Annette Longland, Ph.D., presented the results of three studies that investigated pasture intake by ponies. These results provide more insight into the way ponies are managed, particularly in controlling their appetites and their predisposition to laminitis.
Pasture intakes. The researchers were able to verify something horsemen have known for a long time: ponies can eat a lot of grass. Previous estimates and commonly accepted intakes of pasture for mature horses have been 1.5–2.0% of body weight, with higher intakes estimated for growing, pregnant, and lactating horses. This study measured grass intakes of four mature, idle ponies over a six-week period in which the quality (digestibility energy) of grass varied from 2.3 Mcal/kg DM to 2.9 Mcal/kg DM for the mixed grass/legume pastures.
The average intake for the ponies was 3.8% of body weight. During the six weeks, the ponies gained an average of almost 1 kg per day, indicating that at these levels of intake they are not eating to just meet their energy requirement; they are eating to exceed it.
The quality of the pasture influenced the amount the ponies ate, as they consumed an average of 3.4% of body weight on high-quality pastures but consumed more, an average of 4.2% of body weight, on lower quality pasture. The differences in intake suggest high-energy pastures may be more satisfying, so they don’t need to eat as much.
In looking for ways to control the intake of the ponies and to keep them from gaining weight, two methods were studied, restricting access and muzzling.
Restricted turnout intakes. In this study, ponies were taken off 24-hour access and restricted to only three hours of grazing per day. The ponies were turned out at the same time every day and kept otherwise with free-choice access to haylage with low levels of nonstructural carbohydrates (NSC).
The ponies gained an average of 0.34 kg per day over the six weeks. They ate an average of 2-2.2% of body weight in grass and haylage. Compared to 24-hour access to pasture, the restriction was effective in controlling intake to a certain extent.
The most interesting finding in this study was that ponies learned the routine and became more efficient at grazing. During the first week, the ponies ate 0.49% of body weight in grass during the three hours. By the last week of the study, they got down to business immediately upon being turned out, eating 0.91% of body weight by the last week of the study.
Intakes of the haylage decreased as the amount of grass they ate increased. Ponies preferred the palatability of the fresh grass, so they spent all three hours eating when they had the chance. The fact that they were still able to eat almost half of their daily feed requirement in three hours shows that limiting turnout is only moderately effective at reducing intake once the ponies know the routine.
Heat effect on intakes. During the previously described study, there was one week during the six-week study that was unseasonably hot and it had a significant effect on the appetites of the ponies. Ponies ate only 1.6% of body weight total between pasture and haylage during this week, but they consumed an average of 2-2.2% of body weight during the other five weeks. It is not known whether the intakes would have returned to normal if the heat had continued and the ponies had adapted.
Muzzling. In this study, the ponies were allowed three hours on pasture with or without a grazing muzzle and grass intakes were measured. For the remainder of the day, they were stabled on sawdust bedding and fed hay at 1.5% of body weight. They were also exercised three times per week. The grazing muzzle cut intakes by 83%, and ponies were not able to eat more than 0.5 kg of dry matter, which was a significant decrease in caloric intake for the ponies. When they were not muzzled, the ponies ate an average of 0.8% of body weight, about 3.3 kg, during the three hours of turnout.