The short-term buck-to-buck effect refers to the rapid stimulation of LH, testosterone, and sexual behavior in resting males after the introduction of a sexually active (SA) buck, but the long-term effects of such exposure remain unclear. This study investigated whether prolonged exposure to SA bucks stimulates endocrine activity and sexual behavior in recipient males. Recipient males were exposed either to two sexually inactive bucks undergoing sexual activation induced by a photoperiodic treatment (SA; n = 6) or to two sexually inactive (SI) bucks (n = 5). Testosterone concentrations were low and similar between groups before and during the first two weeks after exposure (P > 0.05). Thereafter, testosterone increased in recipient males exposed to SA bucks and remained higher than in those exposed to SI bucks from mid-February to mid-March (P < 0.05), before declining to comparable levels in both groups. By the end of April, testosterone concentrations were higher in males exposed to SI bucks (P < 0.05). At the time of introduction of the stimulus bucks, neither stimulus bucks nor the recipient males exhibited nudging behavior. Thereafter, from late February onward, recipient males exposed to SA bucks exhibited more frequent nudging behavior than those exposed to SI bucks (P < 0.05). These findings demonstrate that prolonged exposure to SA bucks progressively stimulates endocrine activity and socio-sexual behavior in recipient males, providing evidence for a long-term buck-to-buck effect. Notably, behavioral responses persisted even when testosterone declined, whereas delayed hormonal changes in SI-exposed males were not associated with behavioral activation.

Social interactions shape both the physiological and behavioural development of offspring, and poor care/early caregiver loss is known to promote adverse outcomes during infancy in both animals and humans. How affiliative behaviours impact the future development of offspring remains an open question. Here, we used Equus caballus (domestic horse) as a model to investigate this question. By coupling magnetic resonance imaging, longitudinal biobehavioural assessments and advanced multivariate statistical modelling, we found that prolonged maternal presence during infancy promotes the maturation of brain regions involved in both social behaviour (anterior cingulate cortex and retrosplenial cortex) and physiological regulation (hypothalamus and amygdala). Additionally, offspring benefiting from a prolonged maternal presence showed higher default mode network connectivity, improved social competences and feeding behaviours, and higher concentrations of circulating lipids (triglyceride and cholesterol). The findings of the present study underscore the salient role of social interactions in the development of allostatic regulation in offspring.

This study evaluated the effects of the sexual behavior of sexually active bucks and their vocalizations on testosterone secretion in sexually resting males during the non-breeding season. In experiment 1, sexually resting males were exposed to either photoperiod-treated awake or sedated bucks. Awake bucks displayed more nudging behavior than sedated bucks on D0 (54 vs. 0), D1 (60 vs. 0), and D2 (75 vs. 0; P < 0.001). On D1 and D2, sexually resting males joined with awake bucks exhibited more sexual behavior than those joined with sedated bucks (41 vs. 0 and 58 vs. 0, respectively; P < 0.001). Plasma testosterone concentrations increased in both groups after exposure but were higher in males exposed to awake bucks (23.2 ± 3.8 vs. 13.1 ± 1.8 ng/mL; P < 0.01). In experiment 2, males were exposed to live vocalizations of photoperiod-treated bucks transmitted in real time through a microphone-amplifier-loudspeaker system, while control males remained isolated. Testosterone concentrations were higher in males exposed to vocalizations than in controls (10.8 ± 3.1 vs. 6.2 ± 2.8 ng/mL; P < 0.05). Testosterone pulse frequency increased rapidly following the onset of vocalizations but remained stable in controls (6.4 ± 1.3 vs. 4.8 ± 2.0 pulses over the experimental period, P > 0.05). These findings demonstrated that the sexual behavior of sexually active bucks or their vocalizations stimulate testosterone secretion in males during the non-breeding season, indicating that the male-to-male effect is a multisensory phenomenon that stimulate the endocrine responses in sexually resting bucks.

In mammals, olfactory communication between conspecifics is crucial in modulating reproductive function. In anestrous does (i.e. female goats), exposure to hair from sexually active bucks (SAB, i.e. male goats) triggers a luteinizing hormone response that may induce ovulation, the “male effect.” However, the chemicals in buck hair responsible for this effect and the sensory pathways used by the females to detect this information remain insufficiently understood. In this study, we investigated whether sensory cells from the main olfactory epithelium (MOE) and the vomeronasal organ (VNO) of does respond differently to olfactory stimuli from SAB versus wethers (CAS, i.e. castrated bucks) and how this response is influenced by the female reproductive status (breeding season, anestrous, or ovariectomized (OVX)). To explore this possibility, we stimulated freshly dissociated cells of MOE and VNO cells with chloroform/methanol and aqueous extractions from buck hair, and we assessed cell activation using calcium imaging. Regardless of the extraction method, we observed more cells activated by SAB hair compounds than by those from CAS males. More MOE cells from anestrous were activated by both chloroform and aqueous extracts from SAB than MOE cells from breeding season, or OVX does. Most of these responses originated from non-mature olfactory neurons. These findings suggest that females can discriminate buck sexual activity through sensory detection by the MOE and VNO. The increased response in the MOE to SAB hair compounds during the anestrous period suggests that the MOE may play a more significant role in the “male effect” during this period.

Intravaginal sponges impregnated with the progesterone (P4) analogue fluorogestone acetate (FGA) induce synchronous oestrous behaviour and normal ovulatory cycle in goats. To explore alternatives using natural P4 from plants, we developed a method of ethanolic extraction and a specific enzyme immunoassay (EIA) to measure P4 in the different parts of the walnut tree Juglans regia. We found a very high concentration of P4, specifically in the leaves of the three most common French varieties (similar to 100 mg/kg of DM) but not in flowers, fruits, septa, husk, oil or cake. High concentrations of P4-and to a lesser extent its reduction metabolites and phytosterols-were also measured by Gas Chromatography-Mass Spectrometry/Mass Spectrometry in leaf extracts. P4 concentrations were five times higher in October than in June. P4 was detected in 182 varieties of Juglans regia ranging from 35 to 287 mg of P4 per kg of leaf DM. We collected large quantities of leaves over 6 years, which were used to manufacture feed pellets containing 32% of dry leaf for distribution to female goats. To determine their dietary acceptance and their efficacy in terms of P4 blood plasma concentration, three trials in ovariectomised goats and four trials in ovary-intact goats were performed (N = 83). The distribution of 600 g of pellets per day per ovary-intact goat over 3 days, 6 and 4 days before the introduction of males in April allowed us to achieve our objective of a significant increase of P4 plasma concentration to similar to 1.5 ng/mL measured by EIA from 24 to 72 h after the first distribution in the walnut pellet group (n = 13). The two control groups of goats (FGA, n = 12 and control, n = 10) showed no increase in plasma P4. However, despite this high P4 plasma concentration, goats of the walnut group had the same percentages of goats in oestrus at the first ovulation and of goats experiencing short ovulatory cycles after introduction of males (54 and 77%, respectively) as the group of control goats (80 and 90%), whereas the FGA goats showed very different percentages (100 and 0%, P < 0.01). It was concluded that whereas walnut leaves contain a high concentration of P4-and its reduction metabolites and phytosterols-the pellet feeding mode does not allow for restoration of oestrus behaviour and duration of the induced cycle consistently achieved with FGA-impregnated intravaginal sponges.

Male goats stimulated by the "male-to-male effect" for one month and then introduced to anestrous does are as efficient as those stimulated by photoperiod in inducing cyclicity in anestrous does. Here, we determined whether the sexually active (SA) male goats can stimulate reproduction in does and males when housed together in the same flock during the non-breeding season, and whether male goats exposed to the "male-to-male effect" can fertilize does with the same efficiency and timeframe as SA males stimulated by photoperiod. In March, one group of does was kept isolated from male goats, while three other groups were housed with seasonally hypoactive males (SH). In April, the isolated group was joined with two SA male goats (SA group), while the other three groups were managed as follows: one group was joined with two SA male goats (SA + SH group); the second group was joined with two SA male goats which were fitted with aprons to prevent mating (SA-apron + SH group); and the third group was joined with two SH male goats (SH + SH group). The percentages of does that kidded did not differ among SA (73 %), SA + SH (70 %) and SA-apron + SH (76)% groups; however, all three had greater kidding rates than the SH + SH group (29 %). We conclude that SA male goats stimulate the reproductive activity in both does and male goats during non-breeding season when housed together in the same group. Furthermore, male goats stimulated by the "male-to-male effect" can achieve fertility rates and fertilization timeframe comparable to those of SA male goats.

A reduced sense of smell is a common condition in people with cystic fibrosis (CF) that negatively affects their quality of life. While often attributed to nasal mucosa inflammation, the underlying causes of the olfactory loss remain unknown. Here, we characterized gene expression in olfactory epithelium cells from patients with CF using single-nuclei RNA sequencing and found altered expression of olfactory receptors (ORs) and genes related to progenitor cell proliferation. We confirmed these findings in newborn, inflammation-free samples of a CF animal model and further identified ultrastructural alterations in the olfactory epithelium and bulbs of these animals. We established that CFTR, the anion channel whose dysfunction causes CF, is dispensable for odor-evoked signaling in sensory neurons, yet CF animals displayed defective odor-guided behaviors consistent with the morphological and molecular alterations. Our study highlights CF's major role in modulating epithelial structure and OR expression, shedding light on the mechanisms contributing to olfactory loss in CF.

The mammalian olfactory system plays a crucial role in detecting and transducing a diverse array of molecular cues present in the environment influencing in the display of behaviors such as feeding, reproductive function, and avoidance of predators. The recognition of these chemical signals primarily involves activation of olfactory and vomeronasal sensory neurons located in the main olfactory epithelium and the vomeronasal organ, respectively. Calcium imaging is a well-established method in rodents and insects to evaluate sensory cell activity, although its utilization in other species, particularly large mammals, is less prevalent. Here, we describe recent methodological advances using calcium imaging to scrutinize the response patterns of olfactory and vomeronasal sensory neurons isolated from goats and pigs, with potential applications in other species as well. Our approach reports cell responses to olfactory stimuli and provides a method for molecular characterization of the activated cells through immunolabeling. This methodology enables us to analyze the response patterns of single sensory cells aligning them with specific molecular profiles, providing a valuable tool for identifying mammalian chemosignals and their respective receptors.

Background. In subtropical latitudes, where goats are typically raised in rangeland conditions, daily solar radiation may strongly impair reproductive activity in male goats, thus decreasing their fertility. Objective. To assess the effects of solar radiation on plasma testosterone concentrations, sperm production and fertility in well-nourished male goats over the course of 1 year. Methodology. Control males were kept in a shaded pen (n = 5), whereas the solar-exposed males remained in an unshaded pen exposed to direct solar radiation (n = 5). In experiment 1, plasma testosterone concentrations and sperm production were measured. In experiment 2, fertility of solar-exposed and control males was determined when joined with anestrous female goats. Results. Plasma testosterone concentrations varied over time (P < 0.0001), and there was an interaction between time and the groups of bucks (P < 0.001). In solar-exposed males, testosterone concentrations were lower than controls in June, September, December and January (P < 0.05). The total number of spermatozoa per ejaculate and progressive sperm motility varied over time (P < 0.0001), but there was no interaction between time and groups (P > 0.05). The percentage of live spermatozoa and the percentage of cells with abnormalities varied over time (P < 0.0001), and there was an interaction between time and treatment group (P < 0.0001). In solar-exposed males, the percentages of live spermatozoa were lower than controls in June, August, November and December, while in May, this percentage was higher in solar-exposed males than in controls (P < 0.05). The percentage of abnormal spermatozoa was higher in solar-exposed males than in controls from June to December (P < 0.001). The percentage of females that kidded was lower in those joined with the solar-exposed (48%) compared with those joined with control males (79%; P < 0.001). Implications. Providing shade reduces the negative effects of solar radiation on sperm quality and buck’s fertility. Conclusion. Daily exposure to solar radiation deeply altered reproductive activity of bucks. Testosterone concentrations, qualitative sperm production and fertility, were much lower in solar-exposed bucks compared to the control bucks kept under shade.

ABSTRACT Purpose Neuronal ceroid lipofuscinoses (NCL; Batten disease) are a group of rare inherited neurodegenerative disorders caused by mutations in one of 13 ceroid lipofuscinosis neuronal (CLN) genes. The diseases share a common set of symptoms, including motor and cognitive dysfunction, progressive loss of vision, and seizure activity. A naturally occurring model of CLN5 NCL exists in New Zealand Borderdale sheep, which exhibit similar clinical disease and post‐mortem pathology to the human disease. Recent trials of concurrent intracerebroventricular and intravitreal gene therapy in sheep with CLN5 disease confirmed the therapeutic efficacy of this approach. Given the documented natural history of brain volume changes, detected by MRI, in sheep with CLN5 disease, the current study sought to utilize MRI as both a longitudinal readout and cross‐sectional measure of therapeutic efficacy in treated sheep. Method Sheep treated at a pre‐symptomatic timepoint underwent five T1‐weighted structural MRI scans between 5 and 18 months of age. Sheep treated at early and advanced symptomatic disease stages underwent a single MRI at 18 months of age. All scans from treated sheep were compared to historical healthy control and affected untreated sheep at each age. Finding Pre‐symptomatic treated sheep showed growth in intracranial volume at a comparable rate to healthy control sheep over the course of the study. Whilst grey matter volume decreased and cerebrospinal fluid volume increased in treated sheep, this was to a much smaller degree than in untreated affected sheep. The majority of the cortical regions assessed showed stable volumes over the course of the study, with the notable exception of the cerebellum. Both early and advanced symptomatic treated sheep showed intracranial volumes comparable to untreated affected sheep at 18 months of age. However, when individual tissue types were assessed, grey and white matter were significantly larger, and cerebrospinal fluid was significantly smaller in early symptomatic sheep compared to untreated affected sheep, while the same volumes in advanced symptomatic treated sheep were comparable to untreated affected sheep. Cortical regions assessed showed an age‐at‐treatment and dose effect. Conclusion This study has demonstrated that MRI, a clinically relevant outcome measure, can be successfully utilized to assess therapeutic efficacy in a large animal model of CLN5 NCL, both in a longitudinal study and a cross‐sectional study when robust natural history data is available for comparison.

Progesterone (P4) is an endogenous sex steroid hormone involved in the ovulatory cycle and pregnancy of animal species. In sheep and goats, P4 analogues are used to induce synchronized ovulations and oestrus behavior of the females. In humans, P4 from chemical synthesis is used to treat peri-menopausal disorders. However, such molecules are released into aquatic environment and can be a source of pollution, are prohibited in organic farms and go against the trend of “naturality” in animal production as well as in human health. A natural alternative may consist in the extraction and use of P4 in plants. Mammalian hormones were discovered in an increasing number of plant species, including walnut leaves that contain high levels of P4. We compared the content of P4 in leaves of 170 accessions of Juglans regia from the walnut germplasm collection of INRAE Prunus-Juglans Biological Resources Center previously genotyped using the Axiom™ J. regia 700 K SNP array. We conducted a genome-wide association study (GWAS) using multi-locus models. When collected in October, P4 content goes from 34,1 to 287,5 mg/kg dry weight of leaves. The two laciniate accessions have the largest P4 content. We identified seven significant marker-trait associations on chromosomes 1, 2, 3, 6, 7, 15 and 16, and a candidate gene involved in the metabolism of sterols, precursors of plant steroid hormones. Our results raise the huge variability of P4 content within J. regia and propose a candidate gene which may have a role in the control of this variability, opening the way to a potential use of walnut P4 by the pharmaceutical industry towards more natural source of chemical compounds.

Aromatase (Aro+) neurons located in the Bed Nucleus of the Stria Terminalis (BNST) are crucial for the display of both sexual behavior and territorial aggression in naive male mice. The postero-dorsal part of the Medial Amygdala (MeApd) also contains Aro + neurons that are required for territorial aggression, but these neurons seem dispensable for the display of sexual behavior in naive animals. However, little is known about how Aro + neuron circuitry is influenced by social experience. Using a combination of chemogenetics, activity mapping and retrograde viral tracing, we show that social experience modulates Aro + neurons during sexual behavior and territorial aggression. Chemogenetic inhibition of BNST Aro + neurons in socially experienced male mice revealed that these neurons are required for territorial aggression, but not for sexual behavior. Behavior testing in experienced animals showed a specific increase in activation in the vomeronasal organ (VNO) and the Medial Amygdala (MeA) after sexual behavior but not territorial aggression, assessed by Egr1 expression. We also observed an increase of Egr1 cells in the medial Preoptic Area (mPOA), a brain region implicated in the display of sexual behavior. Combined retrograde viral tracing and Egr1 immunodetection showed that a subset of the activated cells in the MeA are Aro + neurons projecting to the mPOA. These results highlight that social experience induces a differential neural activity in the circuitry controlling sexual behavior and aggression, which include MeA Aro + neurons projecting to the mPOA.

At temperate and polar latitudes, animals and humans experience seasonal changes that impact physiology and behavior. In these habitats, the prevalence and severity of certain psychiatric disorders fluctuate seasonally. Such patterns imply that an adaptive system fine-tunes brain physiology in response to annual environmental changes, and alterations to this system may adversely affect mental health. To date, the core neuronal circuitry of the seasonal control of brain functioning is still largely unknown. To address this question, we identified brain regions sensitive to seasonal changes, using neuroimaging in the domestic sheep (Ovis aries), an animal model commonly used to study seasonality. Here, we developed MRI neuroinformatics resources (templates and atlas) dedicated to the analysis of the sheep brain and revealed that seasons broadly modify grey matter organization and volume of both cortical and subcortical regions involved in the control of homeostasis, sensory processing, learning, memory, behavior control, and social cognition. Many of these regions were not previously known to be affected by seasonal variations, highlighting that the seasonal control of brain function involves plasticity mechanisms across multiple brain sites.

Seasonality of reproductive activity in rams and bucks is the major constraint in temperate and subtropical zones. Rapid alternation between 1 month of short days and 1 month of long days (LD) over three years in lightproof buildings eliminates this seasonality. We examined if this would also work in open barns, using only supplementary light. Over two years, one group of bucks (n = 7) was subjected to alternate 1 month of LD and 1 month of permanent light (LD-LL) and another group (n = 7) to alternate 1 month of LD and 1 month of natural light (LD-NL). A simultaneous control group, used for both experiments (CG1, n = 6; CG2, n = 6), remained under natural photoperiod. BW, testis weight (TW), plasma testosterone (T) and cortisol (C) were evaluated in all bucks. CG1 and CG2 bucks showed identical dramatic seasonal variations in BW (stable or decreasing in summer), TW (from 85 +/- 12 g in February to 127 +/- 7 g in July) and T (from 2.7 +/- 1.2 ng/mL in January-April to 24.3 +/- 3.2 ng/mL in June-October). By contrast, BW of LD-LL and LD-NL bucks increased regularly during the experiment. From 5 and 9 months after the experiment onset, LD-LL and LD-NL bucks, respectively, maintained constant TW of 115 +/- 5 g until the experiment end. After the first 3 months <5 ng/mL, T of LD-LL bucks remained constant (5-10 ng/mL) until the experiment end. By contrast, T of LD-NL bucks showed four periods of low (<5 ng/mL) and two periods of high concentrations (18.1 +/- 2.6 and 11.9 +/- 3.4 ng/mL). Plasma C remained low (5-8 ng/mL) and did not change with group or light treatment. These results show for the first time in any seasonal photoperiodic species that it is possible to maintain the sexual activity of males all year round in open buildings using alternating periods of LD and LL. By contrast, return to NL instead of LL every other month does not prevent seasonality in T concentration. These results raise interesting questions about the photoperiodic control of neuroendocrine regulation of seasonal sexual activity and suggest that these treatments can be used to manage males in open barns in farms and in artificial insemination centres. (Spanish and French versions of the full text are available as Supplementary Materials S1 and S2).(c) 2023 The Authors. Published by Elsevier B.V. on behalf of The Animal Consortium. This is an open access article under the CC BY license.

Background. In seasonally anovulatory goats, sexually active bucks led a high pregnancy rate during a mating period of 36 days. Progesterone priming of does can reduce the length of the mating period while maintaining high fertility by allowing oestrous behaviour at the first male-induced ovulation. Objective. To determine whether high fertilization rates could be achieved by using two sexually active bucks, alternated daily for a period of seven days in four successive groups of does. Methodology. Two control bucks were used only with one group of does (n = 19), whereas two experimental bucks were successively housed with four groups of does (n = 18 or 19 each). One of the control and experimental bucks was introduced to their respective groups in the morning and removed 24 h later to rest for 24 h. Immediately after the removal of the first buck, the second buck was placed with the group of does. Each doe was treated with 25 mg of progesterone im 48 h prior to the first introduction of bucks to reduce short ovulatory cycles. Results. In each group, the proportion of does that ovulated was higher than 93%. These proportions did not differ among groups exposed to the control or experimental bucks (P > 0.05). In each group, the proportion of pregnant does was higher than 78%; proportions did not differ among groups (P > 0.05). Implications. At farms with few bucks, efficient management of sexually active bucks can yield a high percentage of pregnant females. Conclusion. These results indicate that two sexually active bucks housed with four successive groups of progesterone-treated anovulatory does during a mating period of seven days were able to achieve high pregnancy rates.

Many species, including humans exhibit a wide range of social behaviors that are crucial for the adaptation and survival of most species. Brain organization and function are shaped by genetic and environmental factors, although their precise contributions have been relatively understudied in the context of artificial selection. We used divergent lines of quail selected on their high versus low level of motivation to approach a group of conspecifics (S + and S-, respectively) to investigate the influence of genetic selection and early social environment on sociability. We observed distinct sex- and brain-region-specific expression patterns of three neuronal markers: mesotocin, and vasotocin, the avian homologues of mammalian oxytocin and vasopressin, as well as aromatase, the enzyme that converts androgens into estrogens. These markers displayed pronounced and neuroanatomically specific differences between S + and S- quail. Additionally, in a second experiment, we assessed the influence of early social environment on social skills in juvenile birds. Mixing S + and S- resulted in more S- males approaching the group without affecting the sociability of S + or other behaviors, suggesting that the early social environment may influence the results of genetic selection. In conclusion, the divergent quail lines offer a valuable model for unraveling the neuronal and behavioral mechanisms underlying social behaviors.

Early exposure of does to sexually active bucks triggers early puberty onset correlating with neuroendocrine changes. However, the sensory pathways that are stimulated by the male are still unknown. Here, we assessed whether responses to olfactory stimuli are modulated by social experience (exposure to males or not) and/or endocrine status (prepubescent or pubescent). We used a calcium imaging approach on goat sensory cells from the main olfactory epithelium (MOE) and the vomeronasal organ (VNO). For both cell types, we observed robust responses to active male hair in females under three physiological conditions: prepubescent females isolated from males (ISOL PrePub), pubescent females exposed to males (INT Pub) and isolated females (ISOL Pub). Response analysis showed overall greater proportion of responses to buck hair in ISOL PrePub. We hypothesized that females would be more responsive to active buck hair during the prepubertal period, with numerous responses perhaps originating from immature neurons. We also observed a greater proportion of mature olfactory neurons in the MOE and VNO of INT Pub females suggesting that male exposure can induce plastic changes on olfactory cell function and organization. To determine whether stimulation by male odor can advance puberty, we exposed prepubescent does to active buck hair (ODOR). In both ODOR and females isolated from males (ISOL) groups, puberty was reached one month after females exposed to intact bucks (INT), suggesting that olfactory stimulation is not sufficient to trigger puberty.

Sexually hyperactive bucks are more efficient than sexually hypoactive bucks in stimulating testosterone secretion and sexual behaviour in other bucks in seasonal sexual rest by the phenomenon that we called the “buck-to-buck effect”. Here, we determined whether physical separation and reduction of duration of contact with the sexually hyperactive bucks would modify those parameters in sexually hypoactive bucks exposed to the “buck-to-buck effect”. Bucks were subjected to natural day length throughout the study, this was the sexually hypoactive group. Other bucks were subjected to artificial long days (16 h of light per day) from 15 November to 15 January followed by exposure to natural day length to stimulate their sexual activity during the rest season, this was the sexually hyperactive group. In Experiment 1, we determined testosterone concentrations and sexual behaviour of 6 sexually hypoactive bucks separated 1.5 m from 6 sexually hyperactive bucks for 60 days by a metal open work fence, while a control group of 6 sexually hypoactive bucks was in permanent contact with 6 sexually hyperactive bucks. In Experiment 2, the duration of contact with sexually hyperactive males was reduced from 31 days (contact group, 6 bucks) to 10 days (withdraw group, 7 bucks). In experiments 1 and 2, there was an effect of time (P < 0.01) and an interaction between time and groups (P < 0.05). In Experiment 1, testosterone plasma concentrations were greater in bucks in contact with sexually hyperactive bucks than in those separated from bucks at 20 and 30 days after introduction of sexually hyperactive bucks (P < 0.01). The bucks from the contact group also displayed more nudging than bucks from the separated group from 0 to 30 days (P < 0.001). In Experiment 2, testosterone concentrations were greater in contact group than in those from the withdraw group from 19 to 31 days after introduction of sexually hyperactive bucks (P < 0.05). Bucks from the withdraw group displayed more nudging than the contact group 7 days after the introduction of the sexually hyperactive bucks (P < 0.05). Afterwards, bucks from the contact group displayed more nudging than the withdraw group 14, 21 and 28 days after the introduction of the sexually hyperactive bucks. We concluded that physical separation and reduction of duration of contact with the sexually hyperactive bucks decrease testosterone concentrations and sexual behavior of bucks in sexual rest exposed to the “buck-to-buck effect”.

In goats, early exposure of spring-born females to sexually active bucks induces an early puberty onset assessed by the first ovulation. This effect is found when females are continuously exposed well before the male breeding season starting in September. The first aim of this study was to evaluate whether a shortened exposure of females to males could also lead to early puberty. We assessed the onset of puberty in Alpine does isolated from bucks (ISOL), exposed to wethers (CAS), exposed to intact bucks from the end of June (INT1), or mid-August (INT2). Intact bucks became sexually active in mid-September. At the beginning of October, 100% of INT1 and 90% of INT2 exposed does ovulated, in contrast to the ISOL (0%) and CAS (20%) groups. This demonstrated that contact with males that become sexually active is the main factor prompting precocious puberty in females. Furthermore, a reduced male exposure during a short window before the breeding season is sufficient to induce this phenomenon. The second aim was to investigate the neuroendocrine changes induced by male exposure. We found a significant increase in kisspeptin immunoreactivity (fiber density and number of cell bodies) in the caudal part of the arcuate nucleus of INT1 and INT2 exposed females. Thus, our results suggest that sensory stimuli from sexually active bucks (e.g., chemosignals) may trigger an early maturation of the ARC kisspeptin neuronal network leading to gonadotropin-releasing hormone secretion and first ovulation.

Twelve rams were used to confirm whether rams sexually activated in spring by light treatment increase social and sexual activities of non-treated rams in the presence of ewes. Males were divided into 2 groups: light-treated rams (group L, n = 6), which were exposed to artificial long days (16 h light) for 2 months (1 Nov-31 Dec), or non-exposed, control rams (group C, n = 6), exposed to the natural pho-toperiod. At the end of the long-day period, light-treated rams were returned to the natural photoperiod, groups isolated from each other. In mid-Feb, 3 rams from each group were put together such that 4 ex-perimental groups were created: the remaining light-treated rams (L, n = 3), the remaining control rams (C, n = 3), and the other treated (L-mixed n = 3) and non-treated (C-mixed, n = 3) rams, exposed to 30, 30, and 60 ewes, respectively, in 3 separate paddocks. To identify each ram, large (30-cm-high) numbers were painted on the sides and rump of the males with washable sheep spray paint. Behaviors were doc-umented by 4 video cameras using 6 30-minute segments from 1600 to 1800 h the following day (27 hours). C rams presented the lowest proportion of activities ( P < 0.01), and C-mixed rams exhibited pro-portions similar to L and L-mixed rams. C rams exhibited the fewest fight attempts ( P < 0.001), fighting ( P < 0.05), pushing ( P < 0.001), and sniffing another ram. The groups differed significantly ( P < 0.001) in pushing, pawing, flehmen, and attempt mounting, and C rams had the fewest interactions. In conclusion, rams exposed to 2 months of long days at late-autumn early-winter increased social and sexual activities of unexposed rams. These observations can be explained by a "ram-to-ram effect", which can enhance the endocrine activity of rams in sexual rest if they are joined with rams who have been made sexually active by a photoperiodic treatment. These findings suggest that socio-sexual interactions could be used to restrict out-of-season reproduction in this species.(c) 2022 The Author(s). Published by Elsevier Inc.This is an open access article under the CC BY license ( http://creativecommons.org/licenses/by/4.0/ )