Effects of aflatoxin b 1 on the functioning of hypothalamo-pituitary-gonadal (hpg) axis in male pigs (sus scrofa domesticus)

Abstract

Aflatoxin is a major food contaminant, with adverse effects on the physiology of both humans and animals. Some pathophysiological effects of aflatoxicosis include reduction in growth rate, loss of weight, suppressed immunity, icterus, hemorrhagic enteritis, reduced performance, and consequently death. It has been reported that aflatoxicosis may interfere with reproduction by affecting animal fertility. This study investigated the effects of aflatoxin B 1 (AFB 1 ) on the functioning of the hypothalamo pituitary-gonadal (HPG) axis in male pigs. The objectives of the study were: To investigate the effects of varied levels of AFB 1 on body weight and testicular volume; to determine the effects of varied AFB 1 levels on haematological indices; to determine the effects of different AFB 1 levels on follicle stimulating hormone (FSH), luteinizing hormone (LH), testosterone hormone (TH) and estradiol (E2); and to investigate the histopathological changes caused by AFB 1 on the testes, epididymis, liver, pituitary gland and the hypothalamus. Twelve reproductively mature male Large White pigs of the age of 7 to 9 months were randomly allocated to four groups; one control group and three treatment groups, each group comprising 3 pigs. They were housed in a pig pen. The AFB 1 doses were given in three levels. The first treatment group received 80 ppb per pig per day, second treatment group 160 ppb and the third treatment group 240 ppb per pig per day for 60 days. The control group received aflatoxin-free diet. Body weight and testicular volume were measured once per week. Blood samples were collected at an interval of 7 days for hemoanalysis and hormonal assays. The pigs were sacrificed immediately following termination of the treatment, and their tissues collected and processed for histological examination. Analysis of hormones was carried out using porcine ELISA kits for FSH, LH, testosterone and E2, in a sandwhich ELISA method. The study showed that AFB 1 levels had no significant effect on body weight (P=0.068) while testicular volumes significantly reduced (P=0.001) with increase in AFB 1 levels. White blood cells, red blood cells, haemoglobin and mean corpuscular haemoglobin concentration were significantly reduced (P=0.043, P=0.008, P=0.001, and P=0, respectively) in a dose-related manner. There was a significant increase in the levels of mean corpuscular volume (P=0.017) and mean corpuscular haemoglobin (P=0.047). AFB 1 had no significant effect on platelet count (P=0.086). Granulocytes were not significantly affected by the different aflatoxin levels (p=0.957), while lymphocytes and monocytes decreased significantly (p=0). The plasma levels of LH, testosterone and E2 of the AFB 1 challenged groups decreased significantly (P=0.042, P=0.002 and P=0.001, respectively) with increase in AFB 1 level; AFB 1 did not have significant effect on the level of FSH (P=0.197). Histopathological changes in the testes of the aflatoxin B 1 -treated pigs were; progressive decrease of spermatogenesis cells, progressive reduction of Leydig cells and Sertoli cells, progressive increase in peritubular oedema, necrosis of seminiferous tubules and atrophy of the seminiferous tubules characterized by thickened basement membrane. Epididymis showed epithelia hyperplasia in all pigs treated with AFB 1. Histopathological changes in the liver tissue included; marked bile duct proliferation predominantly in the second (160 ppb) and third (240 ppb) treated groups; dilatation of the central vein; mononuclear cell infiltration; fatty change; fibrosis and marked congestion of the parenchyma. Histology sections of the pituitary gland and the hypothalamus showed normal structures. The findings of this study showed that oral administration of AFB 1 for an extended period of time induced marked physiological and histopathological changes in the testes, epididymis and the liver and may impair the functioning of hypothalamo-pituitary- gonadal axis in male pigs.