Abstract
The hypothalamic-pituitary-gonadal (HPG) axis is a key neuroen-docrine regulation system involved in the growth and reproduction of poultry. High-temperature conditions lead to the physiological dysfunction of target organs of the HPG axis of poultry, ultimately affecting the animals’ growth and development. In this study, we evaluated the effect of heat stress (HS) on the development of cells secreting major reproductive hormones of the HPG axis (i.e., hypothalamus, pituitary gland, ovary, and testis) of Wenchang chicks. Seventy-two one-day-old healthy Wenchang chicks were randomly divided into control (CK) and HS groups. The HS group was placed in a 40 ± 0.5°C artificial climate chamber for heat-stress treatment from 13:00 to 15:00 daily for six consecutive weeks. As development progressed, compared with the CK group, the gonadotropin-releasing hormone (GnRH), follicle-stimulating hormone (FSH), and luteinizing hormone (LH) levels in the hypothalamus and testosterone (T) levers in the testes of male chicks in the HS group were significantly decreased at three weeks of age (p<0.05). However, GnRH levels in the hypothalamus and estradiol (E2) levels in the ovaries of female chicks in the HS group were variable and significantly lower than those of the CK group at four and five weeks of age (p<0.05). In addition, the LH and FSH levels in the pituitary gland were significantly lower than those in the CK group at two and four weeks of age and at four and six weeks of age, respectively (p<0.05). In brief, HS caused dysfunction of the corresponding target organs of the HPG axis in Wenchang chicks, and this affected the normal growth and development of the cells’ HPG axis.
Highlights
With global warming, high-temperature and high-humidity environments in tropical and subtropical regions are increasingly detrimental to the livestock industry
Immunohistochemical analysis revealed that GnRHpositive staining was distributed in the cell bodies and around the nuclei of neurons in the hypothalamic tissues; this is illustrated by a light-brown color and irregular shape (Figure 1)
The gonadotropin-releasing hormone (GnRH)-positive staining in the hypothalamic tissues of the male Wenchang chicks of the CK and heat stress (HS) groups initially increased and declined
Summary
High-temperature and high-humidity environments in tropical and subtropical regions are increasingly detrimental to the livestock industry. When the ambient temperature exceeds the upper limit of the thermoneutral zone of poultry, the body will be under stress, resulting in tissue and endocrine system disorders and suppressed organ development. High temperatures affect the synthesis and secretion of several relevant hormones such as FSH, LH, and E2 (Zhang et al, 2012) Under such environmental circumstances, the body regulates the HPG axis by changing the secretion activities of these hormones. Studies have shown that high temperatures alter the secretion of GnRH in the hypothalamus as well as LH and FSH in the pituitary gland of poultry, leading to the dysregulation of the HPG axis (Elnagar et al, 2010; Chen et al, 2015; Tu et al, 2016). The results provide fundamental information concerning the growth and development of chicks in high-temperature environments
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
