The localization and expression of gonadotropin inhibitory hormone in the hypothalamus of turkey hens during the prepubertal, pubertal and postpubertal phases.

Gonadotropin inhibitory hormone (GnIH), initially discovered in birds as a hypothalamic neuropeptide, inhibits the synthesis and release of gonadotropins by affecting GnRH neurons and gonadotropes. Therefore, it may be a key neuropeptide in reproduction in birds. The aim of the present study was to investigate the prepubertal, pubertal, and postpubertal localization of GnIH and changes in hypothalamic GnIH expression in British United Turkey hens. In prepubertal, pubertal, and postpubertal periods, the brains of turkey hens (n = 15) were removed after fixation. Sections (30 µm) were prepared from the entire hypothalamus and stained immunohistochemically against GnIH antibody. Gonadotropin inhibitory hormone-immunoreactive neurons were observed in the paraventricular nucleus. These neurons were significantly more abundant in the prepubertal turkeys than pubertal and postpubertal turkeys (P < 0.05). The results suggested that GnIH neurons have an important role in regulating the pubertal events in British United Turkey hens.

The long-term oral administration of thyroxine: effects on blood hematological and biochemical features in broiler breeder hens.

Published data on the beneficial effect of short-term administration of thyroxine (T4) in broiler breeder hens to reduce the ascites incidence in their progeny chicks raises the question as to what extent might the long-term maternal administration of T4 affect the blood hematological and biochemical attributes in breeder hens. A total of 70 broiler breeder hens (47-wk-old) were randomly allotted to control or thyroxine treated (T4) groups. Pure T4 (0.3 mg/bird per day) was orally administered to T4 birds for 14 successive weeks, whereas the control group received the drinking water only. Blood samples were obtained from the brachial vein prior to the initiation of the trial as well as weeks 50, 53, 55, 57, 59, and 61 of age. Body weight was decreased but egg production was not affected by T4 treatment. Plasma concentration of T4, but not triiodothyronine (T3), was increased in T4-treated hens (P < 0.05). The total number of leukocytes and erythrocytes were also higher in T4 birds. A significant effect of time was observed for erythrocyte number and plasma cholesterol concentration (P < 0.05). The long-term administration of T4 did not affect the concentrations of serum calcium and plasma total protein, albumin, globulin, cholesterol, triglyceride, high density lipoprotein, low density lipoprotein, very low density lipoprotein, alanine amino transferase, and aspartate amino transferase (P > 0.05). However, serum concentrations of phosphorus, glucose, and alkaline phosphatase were higher in T4 hens as compared to their control counterparts. In spite of differences in circulatory concentrations of a number of traits between the experimental groups, the recorded values were within their reference ranges. Therefore, the administration of T4 for an extended period of time had no apparent adverse effect on the clinical profile in subjected hens, which may practically support the implementation of this preventative treatment as an approach to decrease the ascites incidence; however, a lower incidence rate in the progeny chicks produced from hens receiving T4 for long-term periods of time remains to be elucidated.

Differential expression of RFamide-related peptide, a mammalian gonadotrophin-inhibitory hormone orthologue, and kisspeptin in the hypothalamus of Abadeh ecotype does during breeding and anoestrous seasons.

Gonadotrophin-inhibitory hormone (GnIH) is a novel hypothalamic neuropeptide that was discovered in birds as an inhibitory factor for gonadotrophin release. RFamide-related peptide (RFRP) is a mammalian GnIH orthologue that inhibits gonadotrophin synthesis and release in mammals through actions on gonadotrophin-releasing hormone (GnRH) neurones and gonadotrophs, mediated via the GnIH receptor (GnIH-R), GPR147. On the other hand, hypothalamic kisspeptin provokes the release of GnRH from the hypothalamus. The present study aimed to compare the expression of RFRP in the dorsomedial hypothalamus and paraventricular nucleus (DMH/PVN) and that of kisspeptin in the arcuate nucleus (ARC) of the female goat hypothalamus during anoestrous and breeding seasons. Mature female Abadeh does were used during anoestrus, as well as the follicular and luteal phases of the cycle. The number of RFRP-immunoreactive (-IR) neurones in the follicular phase was lower than in the luteal and anoestrous stages. Irrespective of the ovarian stage, the number of RFRP-IR neurones in the rostral and middle regions of the DMH/PVN was higher than in the caudal region. By contrast, the number of kisspeptin-IR neurones in the follicular stage was greater than in the luteal stage and during the anoestrous stage. Irrespective of the stage of the ovarian cycle, the number of kisspeptin-IR neurones in the caudal region of the ARC was greater than in the middle and rostral regions. In conclusion, RFRP-IR cells were more abundant in the rostral region of the DMH/PVN nuclei of the hypothalamus, with a greater number being found during the luteal and anoestrous stages compared to the follicular stage. On the other hand, kisspeptin-IR neurones were more abundant in the caudal part of the ARC, with a greater number recorded in the follicular stage compared to the luteal and anoestrous stages.