42 Feeding stalled horses a diet high omega-3 fatty acids results in a plasma fatty acid profile similar to horses on pasture

Abstract

Omega-3 fatty acids (O-3) are a popular topic in equine nutrition, but it is not commonly acknowledged that a prevalent source of O-3 in a horse's diet can be from pasture. Pasture is low fat, but O-3 are the largest fraction, and horses on pasture have higher circulating O-3 than horses without pasture access. Therefore, the objective of these studies was to test the hypothesis that a feed high in O-3 that also matches the ratio of O-3:omega-6 (O-6) in pasture, would increase stalled horses’ plasma O-3 and result in a similar fatty acid profile to pastured horses. Three identical trials were completed between 2017 and 2020. Mature American Quarter Horses (n = 10 per trial; 610.5 ± 14 kg BW) were offered 0.9 kg per 454 kg BW Purina Omega Match Horse Feed (OM) and 2.0% BW Timothy hay split into equal meals (0700 a.m., 1300 p.m.) starting on d 1 of the trial. Horses were housed in individual stalls with attached dry lot turnouts for the duration of each study. The feed had a minimum of 3.5% O-3 with an O-3:O-6 ratio of 2.6. Baseline blood samples were obtained via jugular venipuncture into potassium oxalate tubes before transition to the experimental diet (d 0), and all horses were consuming a variety of other PurinaⓇ feeds before transition. Blood samples were collected on d 30 and 60 post dietary transition. Also, at d 60, blood samples were obtained from 10 horses each year at the Purina Animal Nutrition Center (Gray Summit, MO) that had free-choice access to mixed fescue pasture. These 10 horses were also fed 1.8 kg of Purina Strategy to meet nutritional needs and maintain body weight. All samples were obtained before AM feeding, were immediately centrifuged, and plasma collected for analysis. Fatty acids were analyzed via gas chromatographic-mass spectral analysis of fatty acid methyl esters. Data were analyzed using an ANOVA in SAS 9.4 (Cary, NC). All data are mean ± SD, ug/mL. Plasma O-3 levels increased from baseline (2.07 ± 0.54) to d 60 (6.29 ± 1.82) in horses consuming OM (P < 0.05). Conversely, plasma O-6 levels decreased from baseline (47.21 ± 3.86) to d 30 (42.56 ± 5.47) and remained lower at d 60 (43.89 ± 4.78) in horses consuming OM (P < 0.05). At d 60, horses consuming OM had similar plasma levels of O-3 (6.29 ± 1.82 vs 6.76 ± 2.01, P = 0.45) and O-6 (43.89 ± 4.78 vs 42.36 ± 5.80, P = 0.37) as horses on pasture, respectively. In conclusion, a feed formulated with a high level of O-3 can alter horses’ plasma O-3 concentrations until they match those of horses on pasture. This technique is helpful to boost horses’ O-3 values if they cannot tolerate pasture grass or simply do not have access to it.