Bodyweight loss: Limit-fed diets and slow-feed hay nets
Figure 1. Horses were fed from either the stall floor or from a slow-feed hay net.
Modern management strategies including meal feeding and increased duration of stalling have led to the decreased opportunity for horses to forage and socialize and possibly an increase in equine obesity. Changes in blood profiles and hormones can be impacted by different feeding and management systems. In an effort to lessen the effects of meal feeding, researchers have attempted to increase total time of consumption of feedstuffs by decreasing intake rate. The use of slow-feed hay nets represents an opportunity to extend foraging time while feeding a restricted diet to overweight horses in an effort to induce bodyweight loss.
Objectives and methods
The objectives of this study, conducted at the University of Minnesota, were to determine if a limit fed diet combined with the use of a slow-feed hay net would affect body measurements and blood and hormone patterns in overweight adult horses.
Eight adult Quarter horses with an average bodyweight of 1,241 pounds and a body condition score (BCS) of 7.2 were fed hay either off the stall floor (4 horses) or from a slow-feed hay net (4 horses; Figure 1) for 28 days. Horses were fed in individual stalls at approximately 60% of their maintenance digestible energy requirement, split evenly between two meals fed in the morning and afternoon. Bodyweight, BCS, neck and girth circumference and cresty neck score were taken on days 0 and 28. Twenty-four hour blood samplings were conducted on days 0 and 28 and analyzed for glucose, insulin, cortisol and leptin concentrations. Samplings occurred every 30 minutes for 3 hours post feeding, with hourly samples occurring between feedings.
Results of the studyHorses feeding from the stall floor (2.0 hours) took less time to consume their hay meal compared to horses feeding from the hay nets (3.2 hours). This confirms the effectiveness of slow-feed hay nets at slowing hay intake rates which is especially useful when managing stalled horses or when feeding a limit-fed diet. Increasing the time horses spend feeding promotes gut health and has been shown to reduce stereotypical behaviors and the incidence of colic.
All horses lost bodyweight (an average of 79 pounds) over the 28 day period; however, no difference was observed between horses fed from the stall floor or the hay nets. It has been well established that a sustained, moderate-energy deficient diet results in the loss of both fat and lean body mass. Caloric intakes were designed to be at approximately 60% of digestible energy for adult horses at maintenance to achieve a reduction in 1 BCS unit in 1 month. However, there was no difference in BCS, neck and girth circumference or cresty neck score between day 0 and 28. A possible reason for the inability to detect a change in BCS is the system itself. The BCS systems evaluates adipose tissue in 6 areas, including the ribs, behind the shoulder, along the neck and withers, in the crease of the back, and tailhead. Most of the horses had noticeable visual losses of adipose tissue in their lower abdominal area, a region not considered when assessing BCS.
Only time to peak insulin and peak cortisol were affected by treatment with horses feeding from the hay nets having lower values compared to horses feeding from the stall floor. Greater peak insulin is reflective of the shorter time to consumption from horses fed from the stall floor. These results also indicate that horse feeding from the stall floor had elevated stress, likely due to the shorter time of hay consumption. Average glucose, insulin, cortisol and leptin were affected by day. Glucose and insulin values increased while cortisol and leptin levels decreased throughout the 28-day period. The reduction in cortisol confirms that horses can acclimate to different feeding scenarios over time. Since leptin is a hormone secreted by adipose or fat tissue, a decrease in leptin helps to confirm a loss in adipose tissue during the 28-day period.
The use of a slow-feed hay net coupled with a limit fed diet appears to be an effective method for decreasing bodyweight and maintaining more moderate blood and hormone patterns when feeding overweight adult horses.
Funding for this research was provided by Cargill.