Postprandial insulin responses to various feedstuffs differ in insulin dysregulated horses compared with non‐insulin dysregulated controls

Abstract

Background: Controlling postprandial hyperinsulinaemia is important in insulin dysregulated (ID) horses to reduce the risk of laminitis. Objectives: To evaluate postprandial insulin responses of ID versus non-insulin dysregulated (NID) horses to feedstuffs varying in nonstructural carbohydrate (NSC) and crude protein (CP). Study design: Randomised crossover. Methods: Eighteen adult mixed-breed horses (13.3 ± 2.2 years; 621 ± 78.8 kg) were individually fed [~1 g/kg body weight (BW)] specific feedstuffs within two crossover studies. Eight ID and eight NID were used in Study A, and 11 ID and 5 NID in Study B. In Study A, all horses were randomly fed once: cracked corn (CC: ~74% NSC & ~9% CP), ration balancer with low protein (RB-LP: ~15% NSC & ~17% CP), ration balancer with high protein (RB-HP: ~14% NSC and ~37% CP) and 50:50 mixture of RB-LP:RB-HP (MIX-P). In Study B, horses were randomly fed once: CC, RB-HP, steam-flaked corn (SF: ~73% NSC & ~10% CP), oat groats (OG: ~64% NSC & ~14% CP) and a low NSC pellet (L-NSC: ~6% NSC & ~12% CP). Blood was collected for insulin determination [radioimmunoassay (RIA)] before and 30, 60, 75, 90, 105, 120, 150, 180, 210 and 240-minute post-feeding in Study A and at 60-minute in Study B. Data were analysed via analysis of variance (ANOVA) for repeated measures after any required transformations.Results: ID horses had significantly greater insulin responses (AUCi) than NID for all diets in both studies (P < .001; ID 22 362 ± 10 298 µIU/mL/min & NID 6145 ± 1922 µIU/mL/min). No effect of diet on AUCi for NID (P = .2), but in ID, the CC (32 000 ± 13 960 µIU/mL/min) AUCi was higher than RB-LP (P = .01; 18 977 ± 6731 µIU/mL/min). ID insulin (T60) was lower for the L-NSC (57.8 ± 18.5 µIU/ mL) versus all other diets (P < .02; 160.1 ± 91.5 µIU/mL).Main limitations: Small numbers of horses; no ponies.Conclusions: NSC appears to be the main driver of the postprandial insulin response. ID horses respond disproportionately to feeding even small amounts of low/ | 575 MACON et Al.

Identifying possible thresholds for nonstructural carbohydrates in the insulin dysregulated horse

“…Although neither of the above studies were conducted in the ID animal, practical recommendations were developed from them 9,11 . Therefore, dietary recommendations should be developed in the ID horse 12 …”

“…If individual ID animals require minimal postprandial insulin responses to reduce the risk of HAL, it would be useful to have guidelines for these high‐risk animals. Recent work has shown a possible threshold for starch between 0.024 and 0.054 g/kg bwt and for NSC between 0.076 and 0.191 g/kg bwt in ID horses above which augmented insulin responses may occur 12 . Thus, the current study aimed to elucidate if ID horses do indeed have a threshold (i.e., above which an augmented insulinaemic response occurs which is significantly higher than non‐ID horses' response to the same diet) for NSC, specifically pure WSCs and starch, by evaluating the insulin response (incremental area under the curve for insulin [IAUCi] and peak insulin concentrations) to seven different diets that varied in their WSC and starch content.…”

A one-health lens offers new perspectives on the importance of endocrine disorders in the equine athlete

“…Some caution should be taken with ration balancers that have higher protein, as those have been shown to induce a more pronounced insulin response, albeit not as dramatic as that of higher nonstructural carbohydrate feeds. 95,96 Additionally, if grain is fed, stationary objects placed below the feed are most effective at slowing down the time it takes horses to eat food, which may blunt the postprandial insulin and glucose peaks. 97 Caloric restriction should be undertaken in overconditioned or obese horses to induce weight loss.…”

Nutritional considerations for the management of equine pituitarypars intermediadysfunction

“…Recommendations for the management of animals with ID are aimed at the mitigation of postprandial hyperinsulinaemia, including the restriction of access to grass and forage with NSC contents >10–12% on a DM basis (Geor & Harris, 2013). Recent work has suggested that severely insulin dysregulated animals can have exaggerated insulinaemic responses to even small intakes of complementary feeds, with a threshold of between 0.08 and 0.15 g NSC/kg BW (Macon et al., 2022). Practically, based on this work, severely insulin dysregulated animals should be restricted to 0.1 g NSC/kg BW per meal if a very low insulin response is required.…”