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Abstract
Three studies were conducted to evaluate the effects of dietary ratio of linoleic to linolenic acid on egg production and immune response in Leghorn chickens. Corn oil rich in linoleic acid and flaxseed rich in linolenic acid were used to adjust levels of dietary linoleic and linolenic acids. The first study was conducted to investigate the effects of four dietary ratios of linoleic to linolenic acid [17:1 (control), 8:1, 4:1, or 2:1] in pullet chicks on immune response to standard vaccinations. Dietary ratio of linoleic to linolenic acid did not influence feed consumption and body weight. Decreasing dietary ratios enhanced (P < 0.004) antibody production against Newcastle disease virus (NDV) vaccine at 12 to 16 weeks of age. The dietary ratio of 4:1 or 2:1 enhanced antibody production against infectious bursal disease virus (IBDV) vaccine at 16 weeks of age. The second study was conducted to investigate whether dietary ratio of linoleic to linolenic acid affected egg production parameters and immune response of mature laying hens. Dietary ratio of linoleic to linolenic acid did not affect egg production and quality. Decreasing dietary ratio from 17:1 to 8:1 or 4:1 improved antibody production against NDV vaccine (P < 0.0004) and in vitro lymphocyte proliferation in response to Con A (P < 0.01) or LPS (P < 0.02). The relationship between dietary ratio of linoleic to linolenic acid on subpopulations of blood T lymphocytes was evaluated in a third study. Decreasing dietary ratio of linoleic to linolenic acid from 17:1 to 8:1, 4:1, or 2:1 significantly increased proportion of CD4 +CD8− T lymphocytes, but decreased proportion of CD4−CD8+ T lymphocytes. These observations indicate that supplementing flaxseed as a source of linolenic acid (18:3n-3) to lower dietary ratio of linoleic to linolenic acid improved the immune response of Leghorn chickens without showing negative effects on body weight gain and egg production. The linolenic acid-induced change in blood T-lymphocyte subpopulations may be attributed to the enhancement of immune response.
