Elsevier

Journal of Equine Veterinary Science

Volume 34, Issues 11–12, November–December 2014, Pages 1251-1256
Journal of Equine Veterinary Science

Original Research
The Effect of Feeding Two or Three Meals Per Day of Either Low or High Nonstructural Carbohydrate Concentrates on Postprandial Glucose and Insulin Concentrations in Horses

https://doi.org/10.1016/j.jevs.2014.08.004Get rights and content

Highlights

  • Dietary nonstructural carbohydrate (NSC) and number of meals fed per day can affect insulin dynamics

  • Meal size affects postprandial insulin concentrations

  • Consider feeding management strategies along with NSC content for horses

Abstract

Eight mature idle gelding horses (mean body weight [BW], 558 ± 45 kg) were used in a replicated 2 × 2 Latin square design study. Horses received either two or three meals per day (MPD) for 7 days, of either a high (H; 43%; 215 g/100 kg BW) or low (L; 18%; 90 g/100 kg BW) nonstructural carbohydrate (NSC) concentrate feed to achieve four treatment groups: low NSC in two MPD (L2), low NSC in three MPD (L3), high NSC in two MPD (H2), and high NSC in three MPD (H3). On day 7 of the treatments, blood was collected before (baseline) and for 5 hours after feeding the morning meal (10, 20, 30, 40, 50, 60, 90, 120, 150, 180, 210, 240, 270, and 300 minutes after feeding). Baseline insulin concentrations tended (P = .093) to be higher for horses fed high NSC than low NSC, and horses fed two MPD tended (P = .092) to have higher baseline insulin concentrations than horses fed three MPD. In addition, baseline glucose-to-insulin ratio (GIR) was higher in horses fed high NSC compared with low NSC (P < .001). Horses fed high NSC had higher area under the curve of insulin and higher peak insulin after feeding than those fed low NSC. These findings suggest that NSC content of a concentrate feed has an impact on baseline insulin and GIRs and on postprandial insulin concentrations. Meanwhile, the number (and therefore size) of MPD had fewer impacts on glucose metabolism.

Introduction

The inclusion of starch-rich concentrate feeds is a common practice among horse owners in an effort to increase the caloric density of the horse's diet [1], [2]. The inclusion of meals high in nonstructural carbohydrate (NSC) is associated with increased risk of colic [3] and reduced tissue sensitivity to insulin [4], [5]. If a horse is fed ample concentrate (>2 kg/d), feeding these concentrate meals only one or two times per day may result in larger meal sizes and may result in altered postprandial metabolite concentrations [6], [7], [8], [9], fluid balance [10], and behavior [10], [11].

Repeated postprandial increases in insulin concentration (such as those observed after the intake of large amounts of NSC) appear to decrease the tissue sensitivity to insulin [4], [12]. Insulin resistance (IR) is defined as a decrease in the sensitivity to insulin at tissues such as the liver, skeletal muscle, and adipose tissue [13]. Because of the association of IR with equine laminitis [14], [15] and equine metabolic syndrome [16], [17], it is of interest to identify feeding and managerial practices to reduce the risk of IR development.

Despite potential negative health consequences associated with the feeding of large meals rich in NSC, concentrate feeding is often a necessary component of the diet, particularly for those horses with elevated nutritional needs. Further, concentrate often provides amino acids, vitamins, and minerals lacking in the forage. Therefore, it is of interest to investigate methods that attenuate the risks associated with feeding concentrates. The inclusion of fat and fiber calorie sources to replace NSC calories is one method of decreasing the NSC load for a horse [13], and such a practice may decrease the risk of IR [4]. Decreasing the rate of feed intake by use of obstacles in the feed tub is another method that may be used to minimize the insulinemic response to a high (26%; 52 g/100 kg body weight [BW]) NSC feed [18]. Increasing the number of meals per day (MPD) (if total caloric intake from concentrate is held constant) may have a similar effect, as horses would receive smaller amounts concentrate at each meal and would likely have smaller NSC loads. Smaller meals tend to result in smaller postprandial metabolite changes [6], [8], [19].

The present study was designed to investigate if both meal frequency and dietary energy source affect postprandial changes in glucose and insulin concentrations in horses. It was hypothesized that increasing meal frequency and thus decreasing meal size would have additive benefits to feeding meals with a greater proportion of the calories coming from fat and fiber, rather than from NSC.

Section snippets

Materials and Methods

All research techniques were approved by the North Carolina State University Institutional Animal Care and Use Committee.

Results

All horses maintained BW and condition throughout the study and consumed all feed offered with no complications.

There were no significant interactions between MPD and NSC for any variable assessed. Therefore, the effects of MPD and NSC on metabolite concentrations were not additive and could be considered independently. Glucose and insulin concentrations are shown in Fig. 1.

Discussion

The results of this study show that concentrate feeds rich in NSC have an impact on both baseline and postprandial insulin responses in horses. Horses fed 0.5% of their BW per day of a high NSC concentrate (43% NSC) resulted in elevated baseline insulin concentrations, elevated baseline GIRs, and larger postprandial insulin responses, including the AUCI and the peak insulin concentration after feeding, compared with those fed 0.5% of their BW of a lower NSC concentrate (18% NSC).

The number of

Conclusions

For horses at risk of developing IR and/or equine metabolic syndrome and/or laminitis, it is important to limit NSC intake, by decreasing the concentration of NSC in the feed (hay, pasture, and concentrate) and potentially by decreasing the NSC load at each meal [31]. The results of this work and of others suggest that there may also be some benefit to reducing meal size and consumption rate to reduce the postprandial insulin concentrations [18], [19], [32]; however, more work is required in

Acknowledgments

This article was funded in part by the North Carolina Horse Council.

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