Immune responsiveness of Japanese quail selected for egg yolk testosterone content under severe protein restriction

Effect of blue and red monochromatic light during incubation on the early post-embryonic development of immune responses in broiler chicken

1. The light regime during incubation can influence embryonic and post-embryonic life and its effects can be mediated by rhythmic melatonin production in the embryonic pineal gland.2. This study explored whether the incubation of chick embryos under red or blue monochromatic light, which induces maximum and minimum melatonin production, respectively, can influence the development and reactivity of the immune system in chicks.3. In hatchlings, basal expression of immune genes (AvBD-1, PSEN-1, and IL-6) was evaluated in the duodenum using real-time PCR. The expression of these genes was measured weekly for three weeks after hatching, 3 h after intraperitoneal lipopolysaccharide (LPS) injection. At these times, the heterophile/lymphocyte ratio (He/Ly) was evaluated on blood smears, plasma immunoglobulin Y (IgY) concentrations by ELISA and IL-6 gene expression in the spleen by real-time PCR were determined.4. During development, the He/Ly ratio and plasma IgY concentration were not significantly influenced by the light quality during incubation. Red light increased gene expression of AvBD-1 in hatchlings and IL-6 in two-week-old chickens compared to birds incubated under blue light. The expression of IL-6 after LPS stimulation increased in an age-dependent manner, both in the duodenum and the spleen, reflecting the maturation of the immune system.5. The results suggested that red light may increase the local immune response in the gut immediately after hatching, but this effect was not apparent during later development.

Development and reactivity of the immune system of Japanese quail lines divergently selected for the shape of the growth curve

1. Selection strategies for broilers must balance rapid growth with the welfare and health of animals, strategies must deal with the trade-off with other vital functions.2. Divergent selection of Japanese quail for high (HG) and low (LG) relative body weight gain between 11 and 28 days of age has been conducted to accelerate linear phase growth without influencing the final adult body weight. Higher body growth rate is often connected with a weakened immune system. Therefore, the present study explored the immunological characterisation of quail from HG and LG lines, which differ substantially in their growth rate.3. The trial evaluated the maternal investment to immunologically active substances, cell-mediated immunity stimulated by phytohaemagglutinin (PHA) injection and the acute phase of the immune response to lipopolysaccharide (LPS) administration in three different phases of early postnatal growth.4. Except for higher lysozyme activity in the LG group when compared to the HG line, the maternal investment did not differ between the two lines. Plasma antibody concentrations responded quickly to any change in growth rate in both lines. Overall, it seems that initial rapid growth of the LG line had long-lasting effects on immune responsiveness, even after the growth rate of the HG line escalated during the linear phase of growth.5. The study indicated that changes in the growth rate caused by the selection for growth in meat-type Japanese quail can influence the acute phase of the immune response and development of the immune system.

Temperature-induced variation in yolk androgen and thyroid hormone levels in avian eggs

Global warming has substantially changed the environment, but the mechanisms to cope with these changes in animals, including the role of maternal effects, are poorly understood. Maternal effects via hormones deposited in eggs, have important environment-dependent effects on offspring development and fitness: thus females are expected to adjust these hormones to the environment, such as the ambient temperature. Longer-term temperature variation could function as a cue, predicting chick rearing conditions to which yolk hormone levels are adjusted, while short-term temperature variation during egg formation may causally affect hormone transfer to eggs. We studied the effects of ambient temperature on yolk androgens (testosterone and androstenedione) and thyroid hormones (thyroxine and triiodothyronine) in great tits (Parus major) using data from unmanipulated clutches from a wild population and from aviary birds (ad libitum food) exposed to different experimental temperature treatments during five years. Both in the wild and in captivity, longer-term pre-laying ambient temperature was not associated with clutch mean yolk hormone levels, while the way androstenedione and thyroxine levels varied across the laying sequence did associate with pre-laying temperature in the wild. Yolk testosterone levels were positively correlated with short-term temperature (during yolk formation) changes within clutches in both wild and captivity. We also report, for the first time in a wild bird, that yolk thyroxine levels correlated with a key environmental factor: thyroxine levels were negatively correlated with ambient temperature during egg formation. Thus, yolk hormone levels, especially testosterone, seem to be causally affected by ambient temperature. These short-term effects might reflect physiological changes in females with changes in ambient temperature. The adaptive value of the variation with ambient temperatures pre-laying or during egg formation should be studied with hormone manipulations in different thermal environments.