Can audio–visual or visual stimuli from a prospective mate stimulate a reproductive neuroendocrine response in sheep?

Hawken, Penny; Esmaili, T.; Scanlan, Victoria F.; Blache, Dominique; Martin, Graeme B.

doi:10.1017/s1751731109003954

Cited by 18 publications

(16 citation statements)

References 19 publications

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“…Nonolfactory stimuli also seem to be involved. A recent study reported that anestrous ewes respond to projected images of rams with an increase in LH secretion although the response is less intense compared with that observed in ewes exposed to real rams [32]. In goats, vocalizations also appear to stimulate LH secretion [33].…”

Section: Discussionmentioning

confidence: 96%

No previous isolation of female goats is required for novel males to induce a male effect, especially if direct physical contact is established

et al. 2014

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Section: Discussionmentioning

confidence: 96%

No previous isolation of female goats is required for novel males to induce a male effect, especially if direct physical contact is established

et al. 2014

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“…In a recent study by our group, ewes were seen to respond to photographs of rams with a small increase in LH secretion -the response was muted compared to ewes exposed to the full complement of sociosexual stimuli but it can be inferred that visual stimuli do play a role in mediating the neuroendocrine response of female ungulates to the male effect. Few studies have evaluated the role of auditory stimuli in the male effect but, in the same study, auditory signals from a movie of ewes and rams mating had no effect on pulsatile secretion of LH (50). Nevertheless, auditory stimuli might still be involved in individual recognition: first, auditory signals assist the recognition of lambs by their mothers, particularly from a distance (60); second, some breeds are more reliant on vocal cues than others (57) and, in turn, this could affect the mode or method of individual recognition between males and females.…”

Section: Is Identity Encoded By Olfactory Stimuli From the Male?mentioning

confidence: 99%

“…To address this issue, it is logical to begin with olfactory stimuli because there is general agreement that male odour has an important impact on female reproductive physiology and behaviour (44) and, alone, can induce the entire male effect, from the initial neuroendocrine response through to ovulation (44)(45)(46)(47)(48)(49)(50). Olfactory stimuli are known to mediate individual recognition between males and females of other species (51,52) so a logical hypothesis is that male identity is encoded primarily by an olfactory chemical 'fingerprint' or 'olfactory signature' .…”

Section: Is Identity Encoded By Olfactory Stimuli From the Male?mentioning

confidence: 99%

New understanding of an old phenomenon: uncontrolled factors and misconceptions that cast a shadow over studies of the ‘male effect’ on reproduction in small ruminants

Jorre¹,

Hawken²,

Martin

2014

Turk J Vet Anim Sci

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In female sheep and goats, exposure to males can be used to induce ovulation and thus control and synchronise fertility. This 'male effect' offers simple, cost-effective, and hormone-free management of reproduction in flocks and herds but, despite decades of research, significant gaps in our knowledge impede commercial application. Many of these gaps can be traced back to misconceptions in the early documentation of the male effect, and others are the result of uncontrolled factors in experimental design. Consequently, it is often difficult to draw conclusions from past research, to further our understanding of the phenomenon, and to make recommendations for industry application. Here, we describe 2 aspects of the male stimulus used to elicit the male effect that are often uncontrolled -the novelty of the stimulus males and factors that contribute to variability in the potency of the male stimulus. We discuss the physiology that underpins novelty, including the individual specificity of the sociosexual signals emitted by the male, and the concomitant ability of females to distinguish among individual males and remember them. Importantly, an understanding of the issue of novelty can make it easier to use the male effect in commercial practice. We also discuss difficulties in interpretation caused by variation in endpoints of the male effect (from neuroendocrine reaction to birth). We conclude that more rigour is needed in the control and reporting of male novelty, in preexperimentation separation of the sexes, and in extrapolation from detection of early responses to the male stimulus to reproductive outcomes.

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“…In sheep, the male pheromone seems to be a mix of long-chain fatty acids [34] that might be sufficiently complex to encode the identity of individual males [5]. However, visual stimuli are also important for social communication in sheep [35][36][37][38], and we recently found that projected images of male sheep elicit a small but significant neuroendocrine response in female sheep [39]. Therefore, further studies are required to elucidate the mechanism by which female sheep can discriminate between novel and familiar males.…”

Section: Pheromones and Cell Proliferation In A Female Ungulate 1149mentioning

confidence: 99%

Rapid Induction of Cell Proliferation in the Adult Female Ungulate Brain (Ovis aries) Associated with Activation of the Reproductive Axis by Exposure to Unfamiliar Males1

Hawken

Jorre

Rodger

et al. 2009

Biology of Reproduction

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In many species, the reproductive centers of the brain are profoundly affected by sociosexual stimuli. This is particularly evident in female ungulates such as sheep, in which exposure to males switches them from reproductively quiescent to fertile. In two experiments with female sheep, we tested whether the brain centers that control gonadotropin-releasing hormone (GnRH) neuronal activity respond differentially to ''novel'' vs. familiar males and whether the neuroendocrine response is associated with increased cell proliferation in the hippocampus, a site associated with memory formation. In experiment 1, groups of 10 female sheep that had previously been habituated to males for 3 mo were re-exposed to familiar males or were exposed to novel males. Only the novel males increased luteinizing hormone (LH) pulse frequency, indicating stimulation of GnRH neuronal activity. In experiment 2, groups of six female sheep were injected with bromodeoxyuridine (BrdU) and then maintained in isolation from males or exposed to novel males. Two days later, the hippocampus and hypothalamus were removed and processed for fluorescence immunohistochemistry. Again, exposure to males increased LH pulse frequency. Most important, male exposure also doubled the number of BrdUpositive cells in the dentate gyrus of the hippocampus. No BrdUpositive cells were detected in the hypothalamus. We conclude that the stimulus from novel males switches on the reproductive centers of the brain of female sheep and rapidly doubles the rate of cell proliferation in the hippocampus. The rapidity of this response contrasts with rodents, in which several days of exposure to male pheromones seem necessary for an effect on neurogenesis.

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Can audio–visual or visual stimuli from a prospective mate stimulate a reproductive neuroendocrine response in sheep?

Cited by 18 publications

References 19 publications

No previous isolation of female goats is required for novel males to induce a male effect, especially if direct physical contact is established

No previous isolation of female goats is required for novel males to induce a male effect, especially if direct physical contact is established

New understanding of an old phenomenon: uncontrolled factors and misconceptions that cast a shadow over studies of the ‘male effect’ on reproduction in small ruminants

Rapid Induction of Cell Proliferation in the Adult Female Ungulate Brain (Ovis aries) Associated with Activation of the Reproductive Axis by Exposure to Unfamiliar Males1

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