Master of Science / Department of Animal Sciences and Industry / J. Ernest Minton / It has been well documented that omega-3 PUFA (n-3 PUFA) can confer a wide variety of health benefits to humans and animals. The current study was designed to evaluate the ability of n-3 PUFA to modulate the innate immune response in two diverse breeds of horses. Ten Quarter Horse and 10 American Miniature Horse mares were assigned to either an n-3 PUFA supplemented or control diet (5 full-sized and 5 miniature mares/treatment) for 56 d. The treatment diet was designed to deliver 64.4 mg/kg BW combined eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) daily. Whole blood (20 mL) was collected via jugular veinipuncture into heparinized tubes on 0 d, 28 d, and 56 d. Serum PUFA analysis was conducted by gas chromatography. Peripheral blood mononuclear cell (PBMC) production of tumor necrosis factor-alpha (TNFalpha) in response to toll-like receptor (TLR) ligands lipopolysaccharide (LPS), flagellin, and lipoteichoic acid (LTA) was estimated using an equine-specific ELISA. Peripheral blood samples from d 56 were also analyzed for total and differential leukocyte counts and subjected to flow cytometric analysis. Body type did not affect basal or TLR stimulated TNFα production. Serum PUFA analysis revealed a decrease in linoleic acid (LA) and substantial increases in arachidonic acid (ARA), EPA, DHA, and docosapentaenoic acid (DPA) at both d 28 and 56 in horses fed n-3 PUFA (P less than 0.0001 for all). Dietary n-3 PUFA supplementation reduced (P less than 0.05) un-stimulated basal, but not TLR stimulated TNFalpha production by PBMC’s. Supplementation with n-3 PUFA did not affect total or differential leukocyte counts, nor selected cell surface markers. These results suggest that n-3 PUFA supplementation in the horse can modify circulating PUFA and alter the inflammatory response by reducing basal TNFalpha production. Furthermore, under conditions of the current study and considering the endpoints evaluated, the American Miniature Horse could potentially be used as a model for full-sized horse breeds.

Dwarfism is considered one of the most recognized congenital defects of animals and humans and can be hereditary or sporadic in cause and expression. There are two general morphologic categories within this vastly diverse disease. These categories are disproportionate and proportionate dwarfism and within each of these there are numerous phenotypes which have been extensively described in humans, and to a lesser extent in dogs, cattle, mice, chickens, and other domestic species. Ponies and Miniature horses largely differ from full size horses only by their stature. Ponies are often defined as those whose height is not greater than 14.2 hands; however the maximum height for Miniature horses is constitutionally defined as 8.2 hands. Dwarfism is not considered a desirable genetic trait for Miniature horses. A majority of these conformationally inferior horses showed consistent physical abnormalities typical of disproportionate dwarfisms as seen in other mammal species. A whole genome scan with the Illumina Equine SNP50 chip clearly implicated a region on ECA1 as being associated with dwarfism of horses. The region implicated on the horse chromosome 1 (Equus Caballus; ECA1) contained a candidate gene for dwarfism, aggrecan (ACAN). Mutations were found in Exons 2, 6, 11 and 15 with each mutation associated with a distinct type of dwarfism. These mutations are independently transmitted throughout the population. Absence of normal homozygotes for these mutations and absence of normal horses which were heterozygous for these mutations indicated that these alleles caused dwarfism in those genotypes. These genotypes did not explain all observed dwarves in this population.