Effect of dietary omega-3 fatty acid source on plasma and red blood cell membrane composition and immune function in yearling horses1

Abstract

To determine the effect of different sources of dietary n-3 fatty acids (FA) on plasma and red blood cell (RBC) FA composition and immune response, 18 Quarter Horse yearlings were randomly and equally assigned to 1 of 3 treatments: encapsulated fish oil (n = 6), milled flaxseed (n = 6), or no supplementation (control, n = 6). Fish oil contained 15 g of eicosapentaenoic acid (C20:5n-3) and 12.5 g of docosahexaenoic acid (C22:6n-3), and flaxseed contained 61 g of alpha-linolenic acid (C18:3n-3) per 100 g of FA. Horses had free access to bahiagrass pasture during the active growing season and were individually fed a grain mix concentrate at 1.5% BW/d. Fish oil and flaxseed were mixed into the concentrate in amounts to provide 6 g of total n-3/100 kg of BW. Horses were fed their respective treatments for 70 d. Blood samples were obtained to determine plasma and RBC FA composition and for isolation of peripheral blood mononuclear cells. Peripheral blood mononuclear cells were stimulated with concanavalin A and phytohemagglutinin (PHA) to determine lymphocyte proliferation and were challenged with lipopolysaccharide to determine PGE(2) production. In vivo inflammatory response was assessed on d 70 by measuring skin thickness and area of swelling in response to intradermal injection of PHA. Treatment did not affect BW gain, which averaged 0.6 +/- 0.03 kg/d. Horses fed fish oil had greater (P < 0.05) proportions of eicosapentaenoic acid, docosahexaenoic acid, and sum of n-3 in plasma and RBC compared with those in the flaxseed and control treatments. In addition, plasma arachidonic acid was greater (P < 0.05) and plasma linoleic and alpha-linolenic acids were less (P < 0.05) in the fish oil treatment compared with the flaxseed and control treatments. Dietary treatment did not affect lymphocyte proliferation or PGE(2) production. Across treatments, the peak increase in skin thickness was observed 4 to 8 h after PHA injection. At 4 h postinjection, horses fed fish oil and those fed flaxseed had a greater increase in skin thickness than those in the control treatment (P < 0.05) and horses fed fish oil had a larger area of swelling than those in the control treatment (P < 0.05). Skin thickness remained greater (P < 0.05) in horses fed flaxseed than in control horses 6 h after injection. Although fed to supply a similar amount of n-3 FA, fish oil had a greater impact on plasma and RBC n-3 FA content than did flaxseed. However, supplementing horses with both fish oil and flaxseed resulted in a more pronounced early inflammatory response to PHA injection as compared with nonsupplemented horses.

Omega-3 fatty acid supplementation in horses

“…There is limited conversion of ALA to DHA in humans (Burdge et al, 2001;Arterburn et al, 2006). As stated before, in horses, supplementation with ALA did not lead to increases in circulating DHA (Hansen et al, 2002;Vineyard et al, 2010), only EPA. Feeding of n-3 PUFA to horses may increase circulating levels and increase incorporation into muscle tissue.…”

“…Additionally, they have been used as supplements in equine diets. Horse studies indicated that supplementation with ALA would not lead to increases in circulating DHA (Hansen et al, 2002;Vineyard et al, 2010), only increases in circulating EPA.…”

Fish meal – nutritive value

“…Dietary supplementation with more than 3.3 g EPA + DHA/100 kg BW daily (and in some studies up to 20.7 g EPA + DHA/100 kg BW) has been reported to decrease tumour necrosis factor‐α (TNF‐α), interleukin (IL)‐1, IL‐2, IL‐6 and interferon (IFN)‐γ by mononuclear cell (Calder, 2001). Vineyard et al. (2010) reported that horses fed FO containing 15 g EPA and 12.5 g DHA had higher proportions of EPA, DHA, RBC (red blood cells) and arachidonic acid in their plasma.…”

Incorporation of sunflower oil or linseed oil in equine compound feedstuff: 1 Effects on haematology and on fatty acids profiles in the red blood cells membranes

“…The presence of EPA and DHA was associated with the seasonal availability of ALA in the diet of a grazing horse. In another study (Vineyard et al., ), the ALA provided by pasture grass may have been sufficient to allow EPA and DHA synthesis, which were at sufficiently high concentrations to be detectable in RBC of horses on both control and linseed diets.…”

“…Vineyard et al. () reported a greater impact on plasma and RBC FA composition when linseed was added to the diet. When sunflower oil was added to the diet, the observed significant changes compared to control diet were mainly due to LA presence.…”