Road transport and diet affect metabolic response to exercise in horses

The impact of short-term transportation stress on insulin and oral sugar responses in insulin dysregulated and non-insulin dysregulated horses

BACKGROUND

It is unknown whether short-term transportation affects endocrine responses similarly in horses with and without insulin dysregulation (ID).

OBJECTIVES

To characterise the effect of short-term transportation on stress parameters and insulin responses to an oral sugar test (OST) in horses with and without ID.

STUDY DESIGN

Longitudinal cohort study.

METHODS

Fourteen adult non-pregnant, non-PPID mares of mixed light breeds were grouped as either ID (n = 7) or non-ID (n = 7) based on endocrine testing. Over 2 weeks, horses were transported once, in groups of 3-4 in a horse trailer on a round-trip journey of ~1.5 h. Blood and saliva were collected 24 h and 1 h pre-transportation, directly after unloading and 15 min, 1 h, 3 h plus 24 h post-transportation. An OST was performed 24 h pre-transportation and 3 h post-transportation with a pre- (T0) and post-OST sample collected 60 min later (T60). Heart rates and rectal temperatures were also collected throughout the study. Serum insulin, serum cortisol, and plasma glucose were measured using validated assays. Repeated measures ANOVA were used to determine differences after transportation and between ID and non-ID horses. Non-normal data were log-transformed and multiple comparisons were adjusted using Bonferroni post hoc tests.

RESULTS

Mean insulin was higher in ID horses versus non-ID horses (mean = 109.9 μU/mL vs. 30.2 μU/mL, p < 0.001; 95% CI for mean difference = [55.6-107.7 μU/mL]). Mean serum insulin increased following OST at T60 in ID horses pre- (154.6 μU/mL, p = 0.04; 95% CI = [86.3-223.0 μU/mL]) and post-transportation (284.6 μU/mL, p = 0.03; 95% CI = [114.3-454.8 μU/mL]). Non-ID horses had a mean OST T60 insulin post-transportation of 56.6 μU/mL (95% CI = [29.1-84.1 μU/mL]); above recognised threshold [45 μU/mL] for ID diagnosis.

MAIN LIMITATIONS

Small number of horses, only mares used, and OST not performed immediately post-transportation.

CONCLUSIONS

Performing an OST 3 h following short-term transportation may result in inaccurate ID status.

Short-term transport stress and supplementation alter immune function in aged horses

Long-distance transport is associated with stress-related changes in equine immune function, and shipping-associated illnesses are often reported. Horses are frequently transported short distances, yet the effects of short-term transport on immune function remain largely unknown. Twelve horses, aged 15-30 yr, were assigned to either the control (n = 6) or treatment (n = 6) groups; treatment horses received a daily antioxidant supplement 3 weeks before and after transport. All horses were transported for approximately 1.5-2 hr on Day 0. Blood was collected via jugular venipuncture at 15-min pre- and post-transport and on Days -21, 1, 3, 7, 14, and 21. Body temperature, heart rate, body weight, total cortisol, and gene expression of IFNγ, IL-1β, IL-2, IL-4, IL-6, IL-8, IL-10, IL-12α, IL-17α, SAA1, and TNFα in whole blood were measured. Peripheral blood mononuclear cells were isolated, stimulated with PMA/ionomycin, and stained for IFNγ and TNFα before analysis via flow cytometry. Statistical analyses were performed with significance set at P < 0.05 (SAS 9.4). Transport and supplementation did not appear to affect body weight, heart rate, IL-4, IL-8, IL-12α, IL-17α, change (Δ) in the % and mean fluorescence intensity (MFI) of IFNγ+ lymphocytes after stimulation, or Δ in the % and MFI of TNFα+ lymphocytes after stimulation. Supplementation decreased IL-1β and SAA1 expression. Transport increased total cortisol concentration, body temperature, and IL-2, IL-6, and IL-10 expression but decreased IL-1β, TNFα, and IFNγ expression. Short-term transportation affected physiological, endocrine, and immune responses; supplementation may ameliorate inflammation in aged horses. Immune responses were most altered at 15-min post-transport and typically recovered by Day 1, suggesting that horses may be vulnerable to disease during and almost immediately after short-term transport.

Straw as an Alternative to Grass Forage in Horses-Effects on Post-Prandial Metabolic Profile, Energy Intake, Behaviour and Gastric Ulceration

Simple Summary

Many leisure horses have low energy requirements and obesity is common. Straw has a low energy content and could be a forage option for these horses. However, a previous study suggested that providing straw as the only forage was associated with an increased risk for gastric ulcers. This study evaluated replacing 50% of the daily forage allowance with a good hygienic quality wheat straw. Six horses were fed both the control diet (grass forage only, CON) and the straw diet (50:50 grass forage and straw, S). Each diet was fed for three weeks and all horses were evaluated on both diets. Diet did not affect the prevalence of gastric ulcers. Feed intake time was longer and daily energy intake lower on diet S, compared to CON. Plasma insulin levels were lower on diet S compared to CON, which could be beneficial for horses with overweight or insulin dysregulation. The results suggest that good hygienic wheat straw provided at 50% of the forage ration does not cause gastric ulcers, but may prolong feeding time and promote a metabolic profile more suitable for overweight horses. Including straw as part of the ration therefore may improve welfare for horses with low energy requirements.

Abstract

Straw’s low energy content means it is a roughage option for horses with low energy requirements. Previously, in a field study, straw was associated with an increased risk for gastric ulcers. This study evaluated the effect on gastric ulcers, metabolic profile and behaviour of replacing, in a forage-only ration, 50% of the daily allowance with wheat straw. Six equines were studied in a 2 × 21-day cross-over design. The control diet (CON: 100% grass forage) and the straw diet (S: 50% grass forage and 50% straw [DM basis]) were iso-energetic. Gastroscopy was performed prior to the study and on day 21 and blood samples were collected and behavioural observations were performed. Diet did not affect squamous or glandular gastric ulcer scores (p > 0.05). Feed intake time was longer (p < 0.05) plus energy intake and plasma insulin concentrations were lower on diet S compared to CON (p < 0.0001). Plasma serotonin concentrations tended to be higher on diet S compared to CON (p = 0.05). The results suggest that good hygienic quality wheat straw can be included for up to 50% of the diet without causing gastric ulcers and that it can extend feeding time and promote a metabolic profile more suitable for overweight horses.

Effects of transportation on gastric pH and gastric ulceration in mares

Background

Transportation has been suggested as a risk factor for gastric ulceration in horses, but limited evidence supports this assumption.

Animals

Twenty‐six Standardbred, Thoroughbred, and Warmblood mares from a university teaching herd.

Methods

Twelve mares were confined for 12 hours, overnight, in reproductive stocks with indwelling nasogastric tubes (NGTs) to assess pH of gastric fluid (GF). Gastric ulceration was assessed endoscopically before and after confinement. Subsequently, 26 horses were transported for 12 hours, overnight, in 2 consignments. During transportation, GF was aspirated from indwelling NGT placed in the same 12 mares used in the confinement study, and gastric ulceration was assessed endoscopically before and after transportation in all horses.

Results

The median pH of GF in confined horses was 1.70‐2.49 at each sampling point, and there was no apparent effect on gastric squamous ulcer scores. The median pH of GF from the same 12 horses at corresponding sampling times during transportation was 6.82‐7.22. Transportation was associated with increased gastric squamous ulcer scores, particularly in horses fasted for gastroscopy and NGT placement immediately before departure. Gastric emptying appeared delayed after transportation in horses fed before departure.

Conclusions and Clinical Importance

Transportation is associated with increased gastric squamous ulceration and with increased pH of GF. These findings may be a consequence of impaired gastric emptying and reflux of alkaline small intestinal content, with factors such as duodenal bile salts and short‐chain fatty acids mediating mucosal injury.

Effects of Horse Housing System on Energy Balance during Post-Exercise Recovery

Simple Summary

Horse management aims to keep horses healthy and ensure good performance and animal welfare. Many horses are currently kept in individual box stalls indoors, a housing system that limits free movement, exploration, and social interaction, and may also subject horses to lower air quality. The alternative is a free-range housing system where horses are kept in groups outdoors. Anecdotal information indicates concerns among sports horse trainers that lack of rest in such systems delays recovery and impairs performance. This study examined whether recovery after competition-like exercise in Standardbred trotters was affected by housing system. The results showed that a free-range housing system did not delay recovery in Standardbred trotters, and in fact had positive effects on appetite and recovery of energy balance.

Abstract

This study examined the effects of two housing systems (free-range and box stalls) on recovery of energy balance after competition-like exercise in Standardbred horses. Eight adult geldings (mean age 11 years) were used. The study had a change-over design, with the box stall (BOX) and free-range group housing (FreeR) treatments each run for 21 days. The horses were fed forage ad libitum and performed two similar race-like exercise tests (ET), on day 7 and day 14 in each treatment. Forage intake was recorded during the last 6–7 days in each period. Blood samples were collected before, during, and until 44 h after ET. Voluntary forage intake (measured in groups with four horses in each group) was higher in FreeR horses than BOX horses (FreeR: 48, BOX: 39, standard error of the mean (SEM) 1.7 kg (p = 0.003)). Plasma non-esterified fatty acids (NEFA) was lower at 20–44 h of recovery than before in FreeR horses (p = 0.022), but not in BOX horses. Housing did not affect exercise heart rate, plasma lactate, plasma urea, or total plasma protein concentration. Thus the free-range housing system hastened recovery in Standardbred trotters, contradicting anecdotal claims that it delays recovery. The free-range housing also had positive effects on appetite and recovery of energy balance.