Veterinary Research Forum

Abstract Exposure to extreme temperature conditions such as occurs in certain occupations is known to induce male infertility. In humans and most of the mammals, it has been shown that whole-body heat stress (HS) decreases fertility and produces defective embryos. Hence, the present study aimed at gaining some insights into the mechanisms producing defects after HS. In the present study, 56 mature male Wistar rats were randomly categorized into eight groups (n = 7), including group 1: Control, groups 2: Bioactive peptides (BPs; 10.00 mg kg^-1), groups 3, 4, and 5: Heat-stressed (37.00, 39.00, and 43.00 ˚C for 20 min, respectively), and groups 6, 7, and 8: Heat-stressed along with BPs (10.00 mg kg^-1), respectively. All treatments were administered orally once per day. The HS was induced through the immersion of rat scrotums in a water bath. After 45 days, rats were sacrificed and left testes were removed, fixed, and used for histological and immunohistochemical studies. Harvested right testes were also used for oxidative stress assessments and molecular analyses. Heat stress increased testicular tissue damage, elevated oxidative stress and reactive oxygen species production, and increased germ cells apoptosis, p53 and caspase 3 expressions, and Bax/Bcl-2 ratio. Treatment with BPs as a substance with anti-oxidant properties ameliorated the damage caused by HS. The results of this study highlight the protective role of BPs in the reproductive tract under HS. Bioactive peptides may have potential function against testicular tissue oxidative stress and apoptosis.

Abstract The aim of this study was to examine the effects of heat stress (HS) on the pituitary-adrenal axis and whether the treatments with early-age thermal conditioning (ETC) and vitamin C, alone and in combination, could have a beneficial effect in alleviating these effects. For the experiment, 400 one day-old broilers (both sexes) were used, being divided into four groups. The first group was the control (K), the second group (C) consisted of broilers which received vitamin C from the 22^nd to the 42^nd day via water in the amount of 2.00 g L^-1, in the third group (T), broilers were exposed to ETC for a period of 24 hr at a temperature of 38.00 ± 1.00 ˚C and the fourth group (T + C) was the combination of T and C groups. Immunohistochemically positive adrenocorticotropic hormone (ACTH) cells of broilers in all groups were irregular or stellate and distributed in the periphery and central parts of the pituitary gland, as solitary cells or in clusters. In the T + C group of broilers, a significant increase in the area of ACTH cells (18.91%) and their cores (22.75%), and cortisol level in serum compared to the control group was observed. This reaction of broilers in the T + C group facilitated their adaptation to unfavorable consequences of HS. These results suggest that hypothalamic-pituitary-adrenal axis is stimulated after the exposure to chronic HS, enabling successful adaptation of broilers to adverse conditions.

Abstract Heat stress (HS) has caused relative hypoxia, oxidative stress and high level of homocysteine, which contributes significantly to fertility failures in bulls. The aim of present study was to evaluate the role of dietary betaine (BET) in improving dual purpose Simmental (Fleckvieh) post-thawed semen quality especially during the hottest summer days. A total number of 16 mature bulls were randomly assigned to three equal groups including: 1) Control condition (without betaine), 2) BET1: 57.00 mg of betaine kg^-1 per day and 3) BET2: 114 mg of betaine kg^-1 per day, through daily intakes for 90 days in summer. Plasma levels of homocysteine, seminal plasma antioxidants levels and sperm parameters such as DNA fragmentation, chromatin integrity, motility, viability, morphology and membrane integrity were evaluated. Under maximal HS, serum homocysteine concentrations were reached 16.67 ± 0.09 µmol L^-1. Dietary betaine supplementation influenced DNA fragmentation of sperm and was higher in the control group compared to BET2 group. There were significant decreases in seminal plasma superoxide dismutase (SOD), glutathione peroxidase (GPx) activity and sperm viability and motility in bulls treated with betaine. The activity of GPx and SOD in the control group was increased up to 0.08 ± 0.00 U mg^-1 protein and 0.52 ± 0.01 U mg^-1 protein in seminal plasma. There were no significant differences between groups in the percentage of swollen spermatozoa, membrane integrity, sperm morphology, abnormal head morphology and percentage of spermatozoa stained with aniline blue. In conclusion, BET supplements improved semen parameters in sperm motility, sperm viability and influenced DNA fragmentation during HS with reduction in serum homocysteine concentrations.

Abstract This experiment was carried out to investigate the effects of different levels chromium picolinate (CrPic) and chromium nanoparticles (nano-Cr) on the performance and immune function of broilers under heat stress condition. A total of 320 Ross 308 broiler chicks (from 21 to 42 days) were assigned randomly into eight treatment groups (four replicates per treatment, and 10 chicks per replicate) and be reared at either thermoneutral (21 ˚C) or heat stress (36 ^◦C). The treatments were control (T1) group without supplementation and heat stress, T2 as a heat stress group without supplementation, T3, T4 and T5 groups which were supplemented with 500, 1000 and 1500 ppb CrPic in diet with heat stress, respectively and T6, T7 and T8 groups which were supplemented with 500, 1000 and 1500 ppb nano-chromium in diet under heat stress, respectively. Supplementation of chromium and nano-chromium improved performance including weight gain and feed conversion ratio of heat-stressed chickens. Antibody titers against avian influenza (AI) and infectious bronchitis (IB) at 21 to 42 days of age in broilers fed supplemental chromium and nano-chromium were higher than broiler chickens fed control diet (p < 0.05). Nano-chromium supplementation at level of 1000 ppb and CrPic at level of 1500 ppb improved the antibody titers against AI and IB of broilers under heat stress conditions. It can be concluded from these findings that dietary supplementation of CrPic and nano-Cr can improve performance and antibody titers against AI and IB under heat stress conditions in broilers.

Abstract Sertoli cells are an essential group of cells in seminiferous epithelium which provide nutritional and structural supports for spermatogenic cells via cell junctions. In this study, the gene expression of connexin-43, the most abundantly distributed gap junction protein of cells, was investigated in ram Sertoli cells under mild and severe heat stresses with real-time quantitative PCR. Sertoli cells were isolated from testes of 10 lambs. After culture and 3 passages, they were treated with mild (39 ˚C) and severe (42 ˚C) heat stress for 6 hr. The results showed a significant reduction in the percentage of live cells under severe heat stress compared to the control group (32 ˚C), (p <0.05). Relative quantification analysis revealed significantly higher (3.80 fold increase) values of connexin-43 transcripts in severely heat stressed group than control group (p <0.05). It is concluded that challenging Sertoli cells with 42 ˚C heat could threaten their survival, and overexpression of connexin-43 may cause dysfunction of Sertoli cells due to heat stress. These findings can be useful to identify the molecular mechanisms involved in adverse effects of heat stress on male reproduction and enhance our understanding of its pathogenesis.