Abstract.To study the effects of heat stress (HS) on the growth and reproductive performance of chicks, 1-day-old male Wenchang chicks were randomly selected and divided into control (CK) and HS groups. The two groups of birds were fed according to a routine. The chicks in the HS group were placed under HS for 2 h day −1 (temperature, 40 ± 0.5 • ; humidity, 63.0-80.0 %) until the sixth week. At the end of each week, six chicks were randomly selected from each group and dissected for pituitary and testicular tissues, which were then weighed and sectioned onto slides to observe the histological changes in pituitary and testis under a microscope. Our results indicated that compared with the CK group, with the increase in age, HS significantly reduced the feed conversion rate (FCR) and weight gain per week, and these changes were positively correlated. The pituitary and testicular weights and volumes of chicks in the HS group were significantly lower than those in the CK group (P < 0.05). For 3-week old chicks, the cross-sectional area of seminiferous tubule in chicks of the HS group was extremely significantly lower than that of the CK group (P < 0.01). Compared with the CK group, the seminiferous epithelium was thinner in the HS group, the arrangement of spermatogenic cells became loose and irregular, and the integrity of the histological structure of testicular tissues was also damaged. Therefore, the above results indicated that HS significantly impeded the growth and development of pituitary and testis in chicks.
ABSTRACT:This study aims to investigate the effect of dietary γ-aminobutyric acid (GABA) on the development of thymus tissue structure and function in chicks under heat stress. One-day-old male Wenchang chicks were randomly divided into control group (CK), heat stress group (HS), and GABA+HS group. The chicks from GABA+HS group were administered 0.2 ml of GABA solution daily by oral gavage (50 mg/kg of body weight). Chicks from HS and GABA+HS groups were subjected to heat stress treatment at 40 ± 0.5°C for 2 h every day. Blood and thymus tissue were collected from the chicks at the end of weeks 1-6. Results showed that the thymus weight and index, thickness of cortex, cortex/medulla ratio, number of lymphocytes, activity of superoxide dismutase, total antioxidant capacity, and glutathione peroxidase, and plasma level of tumor necrosis factor-α in HS group were significantly lower than in CK group (P < 0.05). The Toll-like receptor 2 (TLR2) expression in the late stage of heat stress, malondialdehyde (MDA) content, thymocyte apoptosis rate, number of lymphocytes in the S and G2/M phases, and plasma levels of interleukin-4 and interferon-γ in HS group were significantly higher than in CK group (P < 0.05). In contrast, the integrity of thymus tissue structure of GABA+HS group was improved compared with HS group. The TLR2 expression in the early stage of heat stress and the activity of antioxidant enzymes in GABA+HS group were significantly higher than in HS group (P < 0.05), and the MDA content, thymocyte apoptosis rate, number of lymphocytes in the S and G2/M phases, and plasma level of IL-4 and IFN-γ in GABA+HS group were significantly lower than in HS group (P < 0.05). We concluded that heat stress caused structure damage to thymus tissue of chicks, changed the plasma levels of cytokines, reduced the antioxidant activity, and increased cell apoptosis in chick thymus. GABA alleviated the negative effects on the development of chick thymus, improved the immune function of thymus, and played a protective role by regulating the plasma levels of cytokines and antioxidant activity of thymus tissue.
Abstract. This study aims to investigate the changes in the tissue structure,
: Effects of heat stress on somatostatin and some related immune factors in the small intestine of Wenchang chicks. Czech J. Anim. Sci., 62,[446][447][448][449][450][451][452][453][454][455] To investigate the effects of heat stress (HS) on developmental changes in immune functions of chick intestinal mucosa, one-day-old broiler chicks were randomly assigned into control check (CK) and heat-stressed (HS) groups and raised under indoor temperature. The chicks in HS group were subjected to HS at 40 ± 0.5°C from 12:00 to14:00 h every day. Intestinal mucosa samples were collected weekly during 6 weeks, and the effects of HS on somatostatin and its related immune factors were examined using immunohistochemical, physiological, and biochemical methods. The results showed that HS obviously increased the amount and integral optical density of somatostatin positive cells, somatostatin content, as well as IFN-γ and IL-2 levels in the small intestine, and these increases reached statistical significance in some intestinal segments (P < 0.05). In addition, IgG, IgA, and IgM levels fluctuated in different intestinal segments and their levels in jejunum, duodenum, and ileum in 6-week-old chicks were significantly lower in HS group than in CK group (P < 0.05). The contents of immune-related enzymes also fluctuated, but the activities of acid phosphatase, lysozyme, and glutathione reductase in duodenum and jejunum were lower in 6-week-old chicks in HS group than in CK group, some reaching statistical significance (P < 0.05). Growth hormone (GH) and HSP70 contents in multiple intestinal segments in 6-week-old chicks were significantly higher in HS group than in CK group (P < 0.05). The results indicate that (1) HS could increase the expression and secretion of somatostatin and affect the normal development of immunoglobulins, cytokines, and immune-related enzymes in the small intestine, and thereby impact the chicks' intestine immune function; (2) GH and HSP70 in the small intestine were involved in self-protection mechanisms against HS-induced intestinal injury and somatostatin regulation might be one of the important components.
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