Malmgren, L., Andresen, Ø., & Dalin, A. - M. (2001). Effect of GnRH immunisation on hormonal levels, sexual behaviour, semen quality and testicular morphology in mature stallions. Equine vet. J., 33(1), 75–83.
Abstract: Summary The aim of this study was to investigate the effect of gonadotrophin-releasing hormone (GnRH) immunisation on mature stallions that had been used for breeding. Four Standardbred stallions were used in the study: 3 experimental animals and 1 control animal. Semen was collected regularly, i.e. twice/week, during the 4 months prior to the experimental period. The stallions were immunised against GnRH with a GnRH-BSA conjugate. Equimune was used as the adjuvant. The stallions were immunised on 5 occasions, 4 at 2 week intervals, and the fifth 4 weeks after the fourth. Blood samples were taken once a week for analysis of GnRH antibody titre and every third week for testosterone and oestrone sulphate analyses. Semen was collected once a week, and libido and sexual behaviour were observed. Ejaculate volume, sperm concentration, total number of sperm in the ejaculate, sperm motility and sperm morphology were evaluated. Testicular size was measured once a week. At the end of the study, the stallions were castrated, and a histological examination of the testes performed. All immunised stallions produced antibodies against GnRH, and plasma testosterone concentration decreased. However, the effect of immunisation varied between stallions. In 2 of the stallions, high levels of antibodies were found, while in the third, the level was moderate. Four weeks after the first immunisation, a decrease in libido was observed. Two months after the first immunisation, marked changes in semen quality were observed in the 2 stallions with high antibody titres. Fourteen weeks after the first immunisation, the total number of sperm/ejaculate had decreased from >8.6×109 to<2.7×109, sperm motility from >59 to<10% and the frequency of morphological normal spermatozoa had decreased from >60 to<14%. The dominating abnormalities were abnormal head shapes, proximal cytoplasmic droplets and detached heads. In the third stallion, only slight changes in semen quality were found. No changes were observed in the control stallion. Decreases in testicular size were noted in all of the experimental stallions. Pronounced histological alterations in the testes were observed in 2 of the stallions. It is concluded that the vaccine was effective in stimulating production of GnRH antibodies and in suppressing testicular function and androgen secretion. However, there was an individual variation in the responses among the stallions and, further, libido was not totally suppressed.
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Andrew, R. J. (1974). Changes in visual responsiveness following intercollicular lesions and their effects on avoidance and attack. Brain Behav Evol, 10(4-5), 400–424.
Abstract: In the normal chick, conspicuous visual stimuli induce targetting and pecking together, with vocalization. All three are abolished by lesion of the intercollicular area (ICo) or of connections passing through its medial margin. After such lesions, chicks also cease to treat significant visual stimuli as if they were startling and exciting, and may delay response as a result. However, they are still able to recognise, orient accurately to, and respond appropriately to, a variety of complex visual stimuli (e.g. food grains, copulation object). In addition, they are little affected by strange surroundings. Lesion evidence suggests the mammalian subcollicular area to have similar functions to the ICo and to be homologous with it. A route (present in bird), which is well-known in mammals for its association with threat, defense and escape evoked by strange and frightening objects (amygdala-diencephalic periventricular system-central mesencephalic grey, A-DPS-CMG) is stimuli via the 2 ICo (subcollicular area). Two different mechanisms may be involved caudal to the ICo. One consists of tectal afferents which might modulate the evocation of targetting, pecking and other responses via the tectum. The other is the predorsal system of tectal efferents which may mediate such responses. Classical syndromes of tameness and unresponsiveness produced by various interruptions of the A-DPS-CMG route may depend on interruption of connections to these midbrain mechanisms. Attack is depressed by ICo lesions as one aspect of reduced responsiveness to conspicuous and startling visual stimuli. Avoidance, which is apparently mediated by a separate system, much as in Anura, is facilitated.
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Taillon, J., & Côté, S. (2008). Are faecal hormone levels linked to winter progression, diet quality and social rank in young ungulates ? An experiment with white-tailed deer ( Odocoileus virginianus ) fawns. Behav. Ecol. Sociobiol., 62(10), 675–677.
Abstract: Abstract Hormones play a central role in the physiology and behaviour of animals. The recent development of noninvasive techniques has increased information on physical and social states of individuals through hormone measurements. The relationships among hormones, life history traits and behaviours are, however, still poorly known. For the first time, we evaluated natural winter glucocorticoid and testosterone levels in young ungulates in relation to winter progression, diet quality and social rank. Overwinter, levels of glucocorticoid and testosterone decreased, possibly due to the decline of fawns" body mass. The relationships between hormone levels and diet quality were surprising: Fawns fed the control diet presented higher glucocorticoid and lower testosterone levels then fawns fed the poor diet, suggesting that control fawns faced a higher nutritional stress than those on the poor diet. Similarly to other studies on social mammals, we found no relationship between faecal glucocorticoid levels and social rank, suggesting that social stress was similar for dominant and subordinate fawns during winter. Testosterone levels were not correlated to social rank as found previously in groups of individuals forming stable social hierarchies and maintaining stable dominance relationships. The simultaneous suppression of glucocorticoid and testosterone levels suggests for the first time that young ungulates present a hormonal strategy to prevent fast depletion of limited proteins and fat resources during winter.
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Baum, M. J. (2006). Mammalian animal models of psychosexual differentiation: when is 'translation' to the human situation possible? Horm Behav, 50(4), 579–588.
Abstract: Clinical investigators have been forced primarily to use experiments of nature (e.g., cloacal exstrophy; androgen insensitivity, congenital adrenal hyperplasia) to assess the contribution of fetal sex hormone exposure to the development of male- and female-typical profiles of gender identity and role behavior as well as sexual orientation. In this review, I summarize the results of numerous correlative as well as mechanistic animal experiments that shed significant light on general neuroendocrine mechanisms controlling the differentiation of neural circuits controlling sexual partner preference (sexual orientation) in mammalian species including man. I also argue, however, that results of animal studies can, at best, provide only indirect insights into the neuroendocrine determinants of human gender identity and role behaviors.
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Kralj-Fiser, S., Scheiber, I. B. R., Blejec, A., Moestl, E., & Kotrschal, K. (2007). Individualities in a flock of free-roaming greylag geese: behavioral and physiological consistency over time and across situations. Horm Behav, 51(2), 239–248.
Abstract: The concept of personality implies individual differences in behavior and physiology that show some degree of repeatability/consistency over time and across contexts. Most studies of animal personality, particularly studies of individuals' variation in physiological mechanisms, have been conducted on selected individuals in controlled conditions. We attempted to detect consistent behaviors as well as physiological patterns in greylag ganders (Anser anser) from a free-roaming flock living in semi-natural conditions. We tested 10 individuals repeatedly, in a handling trial, resembling tests for characterization of “temperaments” in captive animals. We recorded the behavior of the same 10 individuals during four situations in the socially intact flock: (1) a “low density feeding condition”, (2) a “high density feeding condition”, (3) a “low density post-feeding situation” and (4) while the geese rested. We collected fecal samples for determination of excreted immuno-reactive corticosterone (BM) and testosterone metabolites (TM) after handling trials, as well as the “low density feeding” and the “high density feeding” conditions. BM levels were very highly consistent over the repeats of handling trials, and the “low density feeding condition” and tended to be consistent over the first two repeats of the “high density feeding condition”. Also, BM responses tended to be consistent across contexts. Despite seasonal variation, there tended to be inter-test consistency of TM, which pointed to some individual differences in TM as well. Aggressiveness turned out to be a highly repeatable trait, which was consistent across social situations, and tended to correlate with an individual's resistance during handling trials. Also, “proximity to the female partner” and “sociability” – the average number of neighboring geese in a close distance while resting – were consistent. We conclude that aggressiveness, “affiliative tendencies” and levels of excreted corticosterone and testosterone metabolites may be crucial factors of personality in geese.
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