Effect of type of dietary polyunsaturated fatty acid supplement (corn oil or fish oil) on immune responses in healthy horses.

This research investigated the effects of corn oil and fish oil, both types of polyunsaturated fatty acids, on the immune responses in horses, concluding that both fats might modulate inflammation, but their effect on specific immune responses varies.

Dietary Supplement Assignment

In the study, two randomized groups of horses (five in each group) were assigned to consume a dietary supplement of either 3.0% corn oil or fish oil for 14 weeks. This assignment was part of the study’s investigative process to understand how each polyunsaturated fatty acid could influence the horses’ immune responses and inflammatory factors.

Immune Response Monitoring

Several immune responses were monitored to assess the influence of these dietary supplements. Key factors included:

• Plasma fatty acid profiles: These were monitored to determine whether horses were effectively absorbing the dietary fatty acids from the supplements.
• Cell-mediated immunity: This was evaluated through a delayed-type hypersensitivity (DTH) skin test utilizing keyhole limpet hemocyanin (KLH), a type of protein used to trigger an immune response.
• Humoral immunity: This refers to antibody-mediated immunity and was evaluated by measuring antibody titers—concentration levels—to the KLH protein.

Assessing Inflammatory Responses

The study also examined several inflammatory responses, including:

• Prostaglandin E2 (PGE2) production: Compared between horses fed on corn oil and those on fish oil diet. The corn oil diet showed higher PGE2 production, an inflammatory substance.
• Tumor necrosis factor-alpha (TNF-alpha) expression: Both diets led to higher TNF-alpha production, a protein involved in systematic inflammation, at weeks 6, 8, and 12, in comparison to pretrial values.
• Phagocytosis of latex beads: The study monitored the ability of bronchoalveolar lavage fluid (BALF) cells to engulf and absorb foreign materials, in this case, latex beads. Both diets resulted in increased phagocytic activity at weeks 8 and 12, but there were no significant differences between the two groups.

Interpreting the Findings

• Both dietary polyunsaturated fatty acids led to some modulation of inflammatory responses. However, only corn oil increased the production of PGE2, a proinflammatory substance.
• Neither diet led to observable differences in the DTH skin test and antibody titers to KLH, suggesting similar effects on cell-mediated and humoral immunity.
• The researchers suggested that because the fish oil diet didn’t raise PGE2 production, it may have potential use in treating equine recurrent airway obstruction or other inflammatory diseases in horses.