Alterations in follicular dynamics and steroidogenic abilities induced by heat stress during follicular recruitment in goats

Abstract

We investigated the changes in follicular dynamics and steroidogenic activity during heat stress in goats. Adult female goats were exposed to heat stress at 36 8C and 70% relative humidity for 48 h and then injected with prostaglandin (PG) F 2a (the time of PGF 2a injection was designated as 0 h). In experiment 1, every follicle greater than 2 mm in diameter was monitored by ultrasonography to investigate the follicular dynamics, and plasma concentrations of FSH, LH, progesterone, and oestradiol were measured from 248 h to 120 h. In experiment 2, the follicles were recovered from the goats at 48 h, and the concentration of oestradiol, the aromatase activity, and the LH receptor level in the follicles were determined. In control (non-heatstressed) goats, ovulatory follicles were mainly recruited from 224 h to 0 h, whereas no follicles recruited during that period were ovulated in the heat-stressed goats. The timing of the recruitment of ovulatory follicles was delayed by heat stress by approximately 24 h. The plasma concentration of oestradiol in the heat-stressed goats was significantly lower from 36 to 54 h compared with the controls, although the concentrations of FSH and progesterone did not differ between the treatments. In addition, the concentration of oestradiol, the aromatase activity, and the LH receptor level in the follicles from heat-stressed goats were significantly lower compared with the controls. These results indicate that heat stress during follicular recruitment suppresses subsequent growth to ovulation, accompanied by decreased LH receptor level and oestradiol synthesis activity in the follicles.

Effect of Sexual Deprivation Stress on Bone of Albino Female Rats

“…On the other hand, results of the present study were incompatible with [14] stated that, chronic exposure to stress caused an increase in the estrogen level in female rats and claimed that estrogen has a major role in resisting stress. Also, [15] who stated that the concentration of progesterone in the follicular fluid was higher in cows that had been previously stressed than in non stressed cows .…”

“…( 16 ) This results also explained by that high phosphate leads to reduction of formation of the active form of vitamin D (calcitriol) in the kidneys and this reduces blood levels of calcium ,also decreased calcium level may be due to hyperphosphatemia because hyperphosphatemia can lead to Ca precipitation into soft tissues, . ( 17 ) Results of the present study were in agreement with [14] stated rats exposed to isolation stress leads to hypocalcaemia due to decrease in estrogen secretion which in turn increased renal excretion of calcium and decreased intestinal calcium absorption. An interesting finding of the current study is that the serum phosphorus level showed significant increase in experimental group when compared to control group.…”

The effect of environmental factors and husbandry practices on stress in goats

“…This cortisol is beneficial to the animal to escape from the stressor, but it also has major detrimental consequences. It can compromises successful reproduction (Roth et al, 2000;Ozawa et al, 2005;Hansen,2009;Fatet et al, 2011) and production (Marai et al, 2007;Veerasamy et al, 2010) and increases susceptibility to diseases due to compromised immunity (Leite-Browning, 2007;Abu Elzein & Housawi, 2009;Hosamani et al, 2009).…”

Impacto do estresse térmico sobre a fisiologia, reprodução e produção de caprinos

“…Esta redução é de natureza multifatorial, visto que a hipertermia, causada pelo colapso dos mecanismos termorreguladores, altera e inviabiliza as funções celulares de várias partes e/ou tecidos do sistema reprodutivo (PEREIRA, 2005). No entanto, existem poucos relatos quanto à descrição dos efeitos climáticos sobre as alterações funcionais específicas dos órgãos reprodutivos em fêmeas caprinas (OZAWA et al, 2005).…”

“…URIBE-VELÁSQUEZ et al (2001), com o objetivo de avaliarem os efeitos do estresse térmico Ciência Rural, v.42, n.10, out, 2012. nas concentrações plasmáticas de estradiol e progesterona de cabras Alpinas em lactação, constataram diminuição significativa da secreção plasmática de estradiol e elevação de progesterona quando em estresse térmico, coincidindo com maior temperatura retal das fêmeas. OZAWA et al (2005) verificaram, em fêmeas caprinas expostas a uma condição de estresse térmico (36°C de temperatura ambiente e 70% de umidade relativa) durante o recrutamento folicular, redução significativa na concentração de estradiol, na atividade da enzima aromatase e nos receptores de LH dos folículos, quando comparadas com as fêmeas do tratamento controle.…”