Changes in the Profiles of Serum LH, FSH and Testosterone, and in Mating Performance and Ejaculate Volume in the Ram during the Ovine Breeding Season3

Sanford, L. M.; Palmer, W. M.; Howland, B. E.

doi:10.2527/jas1977.4561382x

Cited by 63 publications

(31 citation statements)

References 30 publications

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“…Since then, ER has also been described in the sheep adrenal gland (Van Lier et al, 2003b), supporting a possible role for oestrogens as modulators of cortisol secretion. Although in our experiment TC did not modify the cortisol response to ACTH in the rams, it cannot be ruled out that this might be due to the type of steroid replacement leading to sustained testosterone levels and not discrete pulses (Sanford et al, 1977). However, Broadbear et al (2005) did not detect differences in cortisol response after HPA stimulation of castrated rams with or without testosterone implant replacement (mean testosterone concentrations 6.11 nmol/l; lower than in the present study).…”

Section: Discussioncontrasting

confidence: 91%

Section: Discussionmentioning

confidence: 77%

“…The levels of 17β-oestradiol in the animals of experiment 1 were pharmacological and the dose of EB was therefore reduced in experiment 2, resulting in lower, yet still pharmacological levels of 17β-oestradiol in those animals. Testosterone levels of the animals in both experiments were within the physiological range, although by intramuscular administration the active compound is usually released into the bloodstream at a relatively steady rate and not in discrete pulses, as occurs in intact rams (Sanford et al, 1977).Cortisol response to ACTH The differences in cortisol response to ACTH in gonadectomised sex steroid replaced sheep confirm our previous findings of sex differences in cortisol secretion in intact sheep (Van Lier et al, 2003a) and expand these findings as in the present study we found differences in cortisol levels of gonadectomised sheep. This is in contrast with earlier studies Turner et al, 2002) where no difference in cortisol response was observed between gonadectomised male and female sheep.…”

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confidence: 81%

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Sex steroid modulation of cortisol secretion in sheep

Lier

Carriquiry

Meikle

2014

Animal

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There is strong evidence that the gonads modulate the hypothalamic-pituitary-adrenal axis. To investigate these sex differences at the adrenal glands of sheep we compared the cortisol response to ACTH (experiment 1) and measured the relative expression of oestrogen receptor alpha (ERS1), androgen receptor (AR), melanocortin 2 receptor (MC2R) and steroid acute regulatory protein (STAR) mRNA in adrenal glands (experiment 2) of gonadectomised rams and ewes either with or without sex steroid replacement. In experiment 1 six castrated adult rams and four ovariectomised adult ewes were used in two ACTH trials. On each trial blood samples were taken every 15 min for 4 h through an indwelling jugular catheter and each animal received 0.5 mg of an ACTH analogue i.v., immediately after the sample at 1 h from the beginning of the trial. Four days after the first trial the males received 100 mg of Testosterone Cyclopentilpropionate (TC) i.m. and the females received 2.5 mg of Oestradiol Benzoate (EB) i.m. At 72 h after TC or EB administration the second trial was performed. In experiment 2 the adrenal glands were obtained from gonadectomised adult rams (n = 8) and adult ewes (n = 8). Four rams received 100 mg of TC i.m. and four females received 0.5 mg of EB i.m. Blood samples were taken at 0, 12, 24, 48 and 72 h relative to steroid replacement and the animals were thereafter slaughtered. Cortisol, testosterone and 17β-oestradiol were determined by radioimmunoanalysis. The transcripts of ERS1, AR, MC2R and STAR were determined by real-time reverse transcription PCR in adrenal tissue. Cortisol secretion was higher in female sheep than in male sheep, and higher in EB-treated than non-treated ewes. No difference in cortisol secretion was observed between TC-treated and non-treated rams. Gonadectomised rams treated with TC presented greater AR mRNA and MC2R mRNA expression than males without the steroid replacement. Gonadectomised ewes treated with EB tended to present lower AR mRNA than the ones without steroid replacement. Gonadectomised rams with TC also had greater AR mRNA, ERS1 mRNA and MC2R mRNA expression than ewes treated with EB. The relative amount of STAR transcript was not different among the different groups. The results confirm sex differences in ACTH-induced cortisol secretion in sheep, as well as in the expression of the receptor proteins for both 17β-oestradiol and testosterone in the sheep adrenal gland. However, the underlying mechanisms for sex steroid modulation remain unresolved.Keywords: sex steroids, gonadectomy, adrenal, receptors, sheep ImplicationsDifferent stressors result in different responses from the hypothalamus-pituitary-adrenal (HPA) axis and stress can reduce reproductive performance in mammals. Considering the different roles of males and females in reproduction, it is reasonable to think that each sex has its own strategy for dealing with the effects of stress. There is abundant evidence that the gonads affect the way the HPA axis responds to stress. Understanding the regulatory pathways of...

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Section: Discussioncontrasting

confidence: 91%

Section: Discussionmentioning

confidence: 77%

mentioning

confidence: 81%

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Sex steroid modulation of cortisol secretion in sheep

Lier

Carriquiry

Meikle

2014

Animal

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“…On the other hand, testosterone application seemed to stimulate accessory glands so that volume of ejaculated increased six-fold in T bucks compared to control bucks. Other researchers (Sanford et al 1977;Kishk 2008) also have observed an increased volume of ejaculates in rams with maximal levels of serum testosterone.…”

Section: Resultsmentioning

confidence: 93%

Seminal characteristics, libido and serum testosterone concentrations in mixed-breed goat bucks receiving testosterone during the non-breeding period

Ángel-García

Meza-Herrera

Guillen-Muñoz

et al. 2014

Journal of Applied Animal Research

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A total of 12 sexually mature mixed-breed goat bucks were used in this experiment to study the effects of testosterone application (T; 25 mg IM every three days during three weeks) during the period of sexual inactivity (end of March, 26°N) on libido, odour, Sertoli cell number, seminal characteristics and serum testosterone levels. The experimental design was completely random with two groups with six bucks in each group. Reaction time was shorter (P < 0.05) in T bucks (96 ± 45 sec) than in control bucks (258 ± 44 sec). Testosterone treatment increased semen volume (1.2 ± 0.5 vs. 0.3 ± 0.03 ml for T and control bucks, respectively) and total sperm cells/ejaculate (1.32 ± 0.7 vs. 0.33 ± 0.02 x 10 9 for T and control bucks, respectively). Buck's odour (scale 1-5) was more intense (P < 0.05) in T bucks (1.8 ± 0.1) than control bucks (0.6 ± 0.2). Serum testosterone levels were threefold higher in T bucks (8 ng/mL) compared to control bucks (2 ng/mL) after three weeks of exogenous testosterone treatment. It was concluded that testosterone application to sexually inactive goat bucks provoke an increase in serum testosterone which in turn induces an intense sexual behaviour and the improvement of semen quality.

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“…In addition, feeding and environmental temperature (according to latitude) may modulate photoperiod effects [10,[19][20][21]. Finally, seasonal effects have been shown to differ among breeds [7,17,24,27]. Testosterone was measured by RIA using an anti-T-3-O-carboxymethyloxime-bovine serum albumin antiserum with a previous ether extraction of experimental sera, as described previously [29].…”

mentioning

confidence: 99%