Male reproductive condition is the limiting factor of efficiency in the male effect during seasonal anestrus in female goats

Hair from sexually active bucks strongly activates olfactory sensory inputs but fails to trigger early first ovulation in prepubescent does

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.

Male-induced early puberty correlates with the maturation of arcuate nucleus kisspeptin neurons in does

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.

The High Testosterone Concentrations of the Bucks Used in the "Male Effect" Is Not a Prerequisite for Obtaining High Ovarian Activity in Goats from Mediterranean Latitudes

Two experiments were carried out. Firstly, 54 anestrous females were placed in contact with photostimulated males (Photo; n = 27) or with no photostimulated males (Natural; n = 27). Moreover, a group of bucks treated with artificial photoperiod and a group of bucks subjected to natural photoperiod without contact with females was used (Photo Isolated and Natural Isolated, respectively). In the Natural groups, the testosterone concentrations were similar except for three days after the introduction of the bucks to the does (19.72 ± 4.11 vs. 2.05 ± 0.25 ng/mL for Natural and Natural isolated bucks, respectively, p < 0.05). However, no differences were observed in the Photo groups during the entire experiment. The percentage of females showing estrous was higher in the group of females in contact with photostimulated bucks (96 vs. 74%, respectively, p < 0.05). In the second experiment, a GnRH agonist, deslorelin, was used to regulate the testosterone concentrations of the bucks. Seventy anestrous females were divided into five groups depending on the treatment received by the bucks to which they were exposed: photostimulated bucks (Photo group, n = 14); photostimulated bucks but treated with the agonist at the onset of the photoperiod treatment (Photo-Ago Long group, n = 13); photostimulated bucks but treated with the agonist at the end of the photoperiod treatment (Photo-Ago Short group, n = 15); bucks receiving no photostimulation but treated with the agonist at the end of the photoperiod treatment period (Natural-Ago Short group, n = 13) and bucks receiving no photostimulation nor agonist (Natural group, n = 15). The agonist treatment increased testosterone concentrations after the injection, which remained high for the entire experiment (p < 0.05). Six days after the introduction of the bucks to the does, the testosterone concentrations increased only in the Natural group reaching similar concentrations to the other groups (12.17 ± 6.55, 16.69 ± 4.53, 8.70 ± 0.61, 11.03 ± 1.45 and 14.42 ± 3.64 ng/mL for Photo, Photo-Ago Long, Photo-Ago Short, Natural-Ago Short and Natural bucks, respectively, p > 0.05). No differences in reproductive parameters were observed (p > 0.05). These results demonstrate that, at Mediterranean latitudes, anestrous females can stimulate the testosterone concentrations of bucks after a period of isolation. The high testosterone concentrations are not a prerequisite for an adequate response to the male effect.

The use of photoperiod-treated bucks to induce a "male effect" does not compensate for the negative effects of nutritional restriction of the females in Mediterranean goats

This work examined the effect of acute nutritional restriction or supplementation one week before male introduction on the reproductive performances of the "male effect" when using photostimulated or control males in goats. On 22 March, 84 anoestrous does were placed with photostimulated bucks or with bucks which had received no treatments. One week before male introduction, the females were provided with different nutritional regimes: Supplemented, restricted or control females. The non-esterified fatty acids (NEFAs) and Insulin Growth Factor-1 (IGF-1) concentrations were measured in the same samples. Fecundity, fertility, prolificacy and productivity were also determined. No interaction between both sources of variation was observed in any of the reproductive variables studied. Treatment of the bucks increased the percentage of females expressing behavioural oestrous associated with ovulation (71% vs 90% for Natural and Photo groups, respectively, P < 0.05). The Supplemented females showed higher ovulation rate than Restricted females (1.77 ± 0.13 vs 1.05 ± 0.05, P < 0.001), fecundity (71% vs 43%, P < 0.05); fertility (76% vs 29%, P < 0.05) and productivity (1.00 ± 0.15 vs 0.29 ± 0.11 kids per female, P < 0.01). In the Supplemented females, the higher reproductive results could be due to the lower NEFAs and higher IGF-1 concentrations at ovulation and at the time of oestrus compared to the Restricted females. Thus, the present experiment results demonstrate that nutrition is an important factor in the response to the "male effect" at Mediterranean latitudes, and its negative effect cannot be counterbalanced by using photostimulated bucks.

Estrus Synchronization in the Sheep and Goat

Estrus synchronization and manipulation are a tool that has been used by producers to provide uniform lamb and kid meat production and dairy sheep and goat milk production, to concentrate work and labor cost, and to plan for the lambing and kidding time. Breeders can also use estrus synchronization to stimulate ewes and does to exhibit estrus and ovulate outside of the breeding season, although both the ovulation rate and pregnancy rate may be decreased. To increase the ovulation rate outside of the breeding season, a variety of estrus synchronization methods have been used.

Photoperiod-Treatment in Mediterranean Bucks Can Improve the Reproductive Performance of the Male Effect Depending on the Extent of Their Seasonality

Simple Summary

On the extensive and semi-extensive goat farms of the Mediterranean region, the induction of the male effect is a common reproductive management practice in spring mating (seasonal anoestrous). The sexual activity displayed by the bucks is one of the main factors that determines the reproductive performance of this practice and, for that reason, it is essential to photostimulate the bucks prior to using it. However, the effectiveness of this photostimulation and the male effect could depend on the seasonality of the breed of buck used. Thus, the present work aimed to compare the efficiency of the male effect, in terms of doe reproductive response and reproductive performance, as induced by bucks made sexually active via photostimulation, from breeds with different reproductive seasonality (Murciano–Granadina, low reproductive seasonality vs. Blanca Andaluza, high reproductive seasonality). The results demonstrated that the Blanca Andaluza bucks subjected to a natural photoperiod and used for the male effect induced a lower percentage of females into oestrus and ovulation, resulting in lower productivity. This suggests that photoperiod-treated bucks efficiently induce the male effect, but photostimulation may be more necessary for breeds with deep seasonality.

Abstract

This study examines the effectiveness of the photoperiod treatment (extra light for 88 days) to render the bucks sexually active during the seasonal anoestrous in order to induce a male effect, depending on the reproductive seasonality of the breed of the bucks used. In April, 57 anoestrous Blanca Andaluza does were distributed into four groups with three males each: 13 were exposed to control Murciano–Granadina bucks (lower seasonality); 15 were exposed to photostimulated Murciano–Granadina bucks; 14 were exposed to control Blanca Andaluza bucks (higher seasonality), and 15 were exposed to photostimulated Blanca Andaluza bucks. After male introduction, the sexual behaviour of the bucks was assessed, and harness marks recorded doe oestrous behaviour. Ovulation was confirmed from plasma progesterone, and the ovulation rate was assessed by transrectal ultrasonography. Fecundity, fertility, prolificacy and productivity were also determined. All of the does in all of the groups showed ovulation. Interaction between both sources of variation was observed: the percentage of females showing oestrous (p < 0.01) and productivity (p < 0.05) was the lowest in the Blanca Andaluza control group (50% and 0.36 ± 0.17 goat kids born/female, respectively). In conclusion, photoperiod-treated bucks efficiently induce a male effect, but photostimulation could be more necessary for breeds with deep seasonality.

Highly precocious activation of reproductive function in autumn-born goats (Capra hircus) by exposure to sexually active bucks

Goats are seasonal breeders with the main cue controlling the timing of breeding season being photoperiod. Hence, the season of birth impacts puberty onset: spring-born goats reach puberty in autumn, at 7 mo of age, whereas autumn-born goats reach puberty at 1 yr during the next reproductive season. The aim of this study was to determine whether exposure of autumn-born young females to sexually active males could counteract the delay in puberty onset observed in autumn-born goats. Females exposed to sexually active males (n = 8) reached puberty earlier than isolated females (n = 8), with exposed females ovulating at a mean age of 3.5 mo. To our knowledge, such precocious puberty onset obtained through social stimulation has never been described in the literature. Moreover, those exposed females exhibited estrus behavior for most ovulations. Our results indicate that in goats born out of season, exposure to sexually active bucks is a really efficient approach to induce early puberty, suggesting that social interactions could have a crucial impact on the regulation of pubertal transition.

Systematic review and meta-analysis of the efficacy of reproductive management practices used to induce resumption of ovarian cyclical activity in anestrous does

Reproductive management practices that use hormones, sociosexual biostimulation, nutritional management, or abiotic factors are used to induce the resumption of reproduction in anestrous does. However, their overall efficacy remains uncertain; therefore, the identification of evidence-based management recommendations to manipulate anestrous in goats is important. Electronic databases were searched to retrieve reports on studies using interventions based on hormonal, sociosexual, nutritional, and abiotic factors. Only experimental studies in which a group of anestrous does was treated and compared against an untreated group were included. Estrus, ovulation, and pregnancy were primary outcomes, whereas the onset of estrus after treatment, the ovulation rate, and the number of anovulatory days were secondary outcomes. Odds ratio (OR) and mean differences were used to synthesize pooled data, and random effects models were used to calculate them. Seventy studies involving 3974 goats met the inclusion criteria. Unclear risk of bias for random sequence generation and allocation concealment predominated across studies. Pooled data for hormonal, sociosexual, and abiotic interventions showed a significant, though variable, increase in estrus (OR range 7.15-144.80), ovulation (OR range 6.08-56.95), and pregnancy (OR range 3.94-30.8). Hormonal treatments significantly reduced the onset of estrus, whereas abiotic interventions failed to reduce the number of anovulatory days. Secondary outcomes were not assessed in trials using sociosexual approaches. Finally, except for pregnancy, no significant efficacy was observed for studies using nutritional management. In conclusion, reproductive management practices using sociosexual approaches showed the highest efficacy for restoring reproductive activity in anestrous does.

The reproductive response to the male effect of 7- or 10-month-old female goats is improved when photostimulated males are used

The exposure of adult, female, Mediterranean goats during anoestrus to males with induced sexual activity via photostimulation, induces a very high percentage of ovulations. The present work examines the ability of photostimulated bucks to improve the male effect-induced reproductive response of young does over that induced by non-stimulated bucks. A 2×2 factorial experiment was designed, consisting of doe age and buck photoperiod treatments. During seasonal anoestrus, 41 does aged 7 (n=19) or 10 (n=22) months were subjected to the male effect on 10 April; half of each group was exposed to males rendered sexually active by prior exposure to 3 months of long days (16 h of light/day) from 31 October (PHOTO bucks), and half to males maintained under the natural photoperiod (CONTROL bucks). Oestrous activity was recorded daily by direct visual observation of the marks left by male-worn marking harnesses over the 32 days following the bringing of the sexes together (introduction). Doe body weight and body condition were determined weekly. Ovulation was detected by measuring plasma progesterone concentrations twice per week over the 3 weeks after introduction. The ovulation rate was assessed by transrectal ultrasonography. Fecundity, fertility, prolificacy and productivity were also determined. The interaction doe age × buck photoperiod treatment had no effect on any outcome. The percentage of females showing ovulation or oestrus was higher in the does exposed to PHOTO bucks (85% v. 43% for those exposed to CONTROL bucks) they also showed higher fertility (75% v. 43%) and productivity (1.05±0.17 v. 0.57±0.16 kids born per doe serviced) (all P values at least P<0.05). The 10-month-old group showed higher percentage of females showing ovulation, oestrus, fertility and productivity than the 7-month-old does after the male effect (females showing ovulation: 82% v. 42%; showing oestrus: 73% v. 42%; fertility: 73% v. 42% and productivity: 1.09±0.17 v. 0.47±0.14 goat kids born per doe serviced; respectively, all P values at least P<0.05). The present results show that the use of photostimulated males improves the reproductive performance of 7- and 10-month-old does, and may contribute towards increasing their productivity and lifetime reproductive performance.

Sexually active bucks are a critical social cue that activates the gonadotrope axis and early puberty onset in does

In rodents, early exposure to adult male is well known to induce an early puberty in females (Vandenbergh effect). This phenomenon has been less studied in other mammals. In goats, despite our extensive knowledge about the "male-effect" phenomenon in adults (i.e. ovulation induced by the introduction of the male during the anestrous), there are few data on the consequences of an early exposure of females to males. Here, we evaluated the puberty onset of young alpine goats when raised since weaning with intact bucks (INT), with castrated bucks (CAS) or isolated from bucks (ISOL). The INT group had the first ovulation 1.5 month before the two other groups. Despite the earlier puberty the INT group of females had normal and regular ovarian cycles. Morphological study of the genital tract showed that at 6 months, uterus of INT goats was 40% heavier than CAS and ISOL goats. Moreover, INT females had a myometrium significantly thicker and INT was the only group having corpora lutea. In our study, INT females were pubescent in the month following the entry of bucks into the breeding season, suggesting that only sexually active bucks provide the signal responsible for puberty acceleration. By removing direct contact with the bucks, we showed that somatosensory interactions were dispensable for an early puberty induction. Finally, no difference in the GnRH network (fiber density and number of synaptic appositions) can be detected between pubescent and non-pubescent females, suggesting that the male stimulations triggering puberty onset act probably on upstream neuronal networks, potentially on kisspeptin neurons.

The use of female estrogenized goats as sexual stimulator of crossbred dairy males subsequently exposed to acyclic goats during two phases of the anestrous season

This research evaluated the possible influence of exposure of male goats to estrogenized female goats ("female effect") upon males' sexual behavior [appetitive (ASB) & consummatory (CSB)], as well as the induction of reproductive activity of crossbred dairy female goats exposed to such treated males ("male effect") during the early and deep anestrous periods. Crossbred dairy adult male goats (n = 12; 24-48 mo. old) and 80 anovulatory crossbred dairy adult female goats (34-50 mo. old) were used during two experimental periods: March to April and April to May. First, males were separated into four groups (n = 3 each), roughly homogeneous regarding body weight and body condition score and randomly assigned to four experimental groups. The first two groups included males + estrogenized females, then such males were exposed to anestrous females either during March (group 1: three males; 20 females; EFEM-MAR), or during April (group 2: three males; 20 females; EFEM-APR). The second two groups were respective control groups: Males + non-treated-anestrous females, and then such males exposed to acyclic females either during March (group 3: three males; 20 females; CONT-MAR) or April (group 4: three males; 20 females; CONT-APR). Once the male-to-female contact was established, both odor (ODT) and behavior (BEHT) tests (2 d × 2 h) were performed during both anestrous periods. On day 10 after introduction of the males, in both anestrous periods, one ultrasonography scanning ("US") was performed to quantify the presence, number and size of corpus luteum (US-CL) to determine the effectiveness of the "male effect" and indicators of ovarian activity. Then, on day 45 after introduction of the males, a second US was performed to evaluate pregnancy rate (US-PREG). The EFEM-males, regardless of the phase of the anestrous cycle, had an increased (P < 0.05) odor intensity with respect to the control groups. In addition, while an increased (P < 0.05) ASB occurred in the EFEM-males, no CSB differences (P > 0.05) arose when treatments were compared, neither in March-April nor in April-May. The EFEM-males exposed to acyclic goats in March-April (i.e. early anestrous period), promoted not only the largest estrus and ovulatory responses (P < 0.05), but also the largest pregnancy rate (P < 0.05) in these previously anestrus goats, suggesting that in April-May (i.e. profound anestrous), the presence of active males was not enough to completely suppress cyclic reproductive arrest. This study generates interesting out-of-season reproductive outcomes in a goat population with a large proportion of highly seasonal dairy breeds (i.e. Alpine, Saanen and Toggenburg), augmenting the possibility to expand milk production and the economic income of goat producers across the year. Besides, this practice may serve as an interesting reproductive tool to increase the sustainability of marginal goat production systems under semiarid conditions.

Influence of sexual behavior of Dorper rams treated with glutamate and/or testosterone on reproductive performance of anovulatory ewes

The aim of this study was to determine if exogenous administration of glutamate and (or) testosterone to male rams during the season of reproductive arrest is able to re-activate male sexual behavior and, later on, to promote through the male effect, both sexual and reproductive competence of anovulatory nulliparous ewes. Therefore, an experiment was performed under long-day photoperiods (spring; photo-reproductive arrest, 26°N). Dorper rams were randomly divided into four homogeneous experimental groups (n = 5 males each) regarding live weight (LW), body condition score (BCS), scrotal circumference (SC) and odor intensity (OI). Then, groups were treated with: i) GG (7 mg kg^-1 LW of glutamate, every 4d × 30d, im.), ii) GGT (7 mg kg^-1 LW of glutamate every 4d × 30d im + 25 mg of testosterone propionate, every 3d × 15d, im.), iii) GT (25 mg of testosterone propionate every 3d × 15d, im, and iv) GC (1 mL of saline, every 4d × 30d, im.). Thereafter, Dorper rams, (n = 4 per group) were selected and exposed to Dorper anovulatory-nulliparous ewes divided in four groups (n = 14 ewes each), and all the appetitive (ASB) and consummatory (CSB) sexual behaviors and indicators of sexual rest (ISR) were registered during the first 48 h of this male-to-females contact. Thereafter, males continued the male-to-female contact for another 8 d, in order to quantify the ewe's sexual and reproductive response through the male effect. During the sexual behavior tests, the GGT rams showed the highest ASB + CSB frequencies (P < 0.05) followed by the GG-rams with the lowest frequencies showed by the GC and GT groups. While the highest ISR behaviors were shown by the GG and GGT groups (P < 0.05) followed by the GC and GT-rams, no differences occurred regarding LW, BCS, and SC along the experimental breeding, with the largest (P < 0.05) OI shown by the GGT-rams and the lowest value observed in the control rams. Regarding the reproductive response of the nulliparous-anovulatory ewes exposed to treated rams, the glutamate + testosterone treated males induced not only an increased (P < 0.05) ovulatory activity and faster (P < 0.05) estrus response but an augmented (P < 0.05) pregnancy rate of the previously anovulatory ewes. To conclude, whereas the GG and GGT treatments generated encouraging sexual and reproductive outcomes, our results are also thought-provoking from a comparative sexual behavior perspective while may embrace potential applications to other animal industries.

Sexually active bucks counterbalance the seasonal negative feedback of estradiol on LH in ovariectomized goats

We showed previously that the permanent presence of bucks rendered sexually active by photoperiodic treatments, thereafter called photostimulated bucks, prevents the occurrence of seasonal anovulation; also, the introduction of these sexually active bucks induces ovulations during seasonal anestrus. Here, we studied the response of ovariectomized goats bearing 12-mm subcutaneous implants filled or not with estradiol to sexually active males to determine (1) whether the permanent presence of such bucks prevents the decrease of LH despite the presence of a negative feedback by estradiol mimicking that of seasonal anestrus (experiment 1) and (2) whether the introduction of photostimulated bucks increases the plasma LH concentrations in spite of this negative feedback (experiment 2). In experiment 1, one group of goats remained in contact with sexually active bucks, whereas the other group remained in contact with control bucks. Plasma LH concentrations were high and did not differ with time or between groups of females from November to February (P > 0.05), when both types of bucks were sexually active. Afterward, in goats in contact with control and sexually inactive bucks, LH concentrations decreased from March (P ≤ 0.01) and remained low until May, whereas LH levels remained high from March to May in goats in contact with the photostimulated bucks (P > 0.05). In experiment 2, 2 groups of females bearing empty subcutaneous implants, and 2 groups of goats bearing subcutaneous implants filled with estradiol, were exposed to control or photostimulated bucks. Plasma LH concentrations did not increase in goats bearing empty implants, when exposed to control or photostimulated bucks (from 2.01 ± 0.26 to 1.98 ± 0.31 ng/mL, and from 2.45 ± 0.29 to 2.42 ± 0.21 ng/mL respectively; P > 0.05). In contrast, plasma LH concentrations increased from 0.97 ± 0.41 to 2.80 ± 0.62 ng/mL in goats exposed to the photostimulated bucks and bearing estradiol implants (P < 0.05). Thus, the permanent presence of sexually active bucks prevented the decrease of plasma LH concentration in OVX + E2 goats during the seasonal anestrus, and the introduction of the photostimulated bucks increased the plasma LH concentrations in OVX + E2 goats during the seasonal anestrus. Therefore, we conclude that in both cases, the photostimulated bucks are able to reduce or counterbalance the seasonal negative feedback of estradiol on LH secretion.

The isolation of females from males to promote a later male effect is unnecessary if the bucks used are sexually active

It has been suggested that female goats in permanent contact with males become refractory to their presence, and need to be previously separated from them for 40-45 days if the presence of bucks is to induce reproductive activity, ovulation and oestrous during seasonal anoestrous. The present study examines the reproductive response (ovulation and oestrus) and reproductive performance of does isolated from bucks for different periods before their reintroduction to male company. A total of 103 Payoya and Blanca Andaluza does were distributed into six treatment groups that required their isolation from males for different periods: 0 days (N = 29), 5 days (N = 15), 10 days (N = 14), 20 days (N = 16), 30 days (N = 14) and 39 days (N = 15). After this period they were introduced to sexually active bucks (ensured to be in this condition by keeping them under long days light treatment for three months), and oestrous activity was recorded daily by direct visual observation of the marks left by the marking harnesses worn by these males. Ovulation was confirmed via the plasma progesterone concentration (measured in blood samples taken twice per week). The ovulation rate was assessed by transrectal ultrasonography. Fecundity, fertility, prolificacy and productivity were also determined. The sexual behaviour of the males towards the females was also monitored on Days 0, 1, 2, 3, 4, 8 and 9 after their meeting with the latter. The length of the female isolation period had no effect on the percentage of does that responded to contact with the males, nor did it affect the oestrous response, fecundity, fertility or productivity. The males, however, undertook more ano-genital sniffing and nudging with the 5 day group females compared to those of the other groups (P < 0.05). However, the sexual behaviour of the males changed as the days passed, with ano-genital sniffing becoming less common, and nudging, licking, sneezing and mounts with intromission more frequent on Days 8 and 9 than on Day 0, 1 and 2 after the sexes were reunited (P < 0.05). These results show that the isolation of females is not necessary for an efficient male effect if the bucks used are sexually active. In addition, the sexual behaviour of the bucks changes as the time in contact with the does increases, but in general is not affected by the duration of female isolation.

Maintaining bucks over 35 days after a male effect improves pregnancy rate in goats

The ovulation can be induced by the introduction of a male among a group of anovulatory goats, a phenomenon called the ‘male effect’. The objective of this study was to determine whether maintaining bucks over 35 days after the initial introduction of males, improves pregnancy rate in goats. We used sexually active bucks, which were joined (n = 2 each) with three groups of goats (n = 30 each): (i) males remained with females for 15 days (Control group); (ii) males remained with females for 35 days (same buck group); (iii) males were removed at Day 23 and replaced by other males, which were not familiar to the females and which remained with females until Day 35 (new buck group). Percentage of goats ovulating did not differ among groups at Day 19 (≥87%; P = 0.12). Pregnancy rates at Day 35 did not differ between groups (≥70%; P = 0.90). At Day 55, pregnancy rates were similar in the same and new buck groups (96%; P = 1.0), but were higher than that of the Control group (73%; P < 0.05). Therefore, maintaining bucks over 35 days after the onset of the male effect improved pregnancy rate more than 20 points compared with females that remained with the same bucks for 15 days only.

A high level of male sexual activity is necessary for the activation of the medial preoptic area and the arcuate nucleus during the 'male effect' in anestrous goats

In small ungulates such as sheep or goats, the introduction of a male among a group of anovulatory females during the anestrus season leads to the reactivation of the gonadotrope axis and ovulation, a phenomenon known as the 'male effect'. In goats, our previous studies have demonstrated the importance of male sexual activity for an efficient reactivation of the gonadotrope axis assessed through ovulation and blood LH pulsatility. In the present experiment, we assessed whether the level of male sexual activity would also induce differential activation of two brain regions of key importance for the reactivation of GnRH activity, namely the medial preoptic area and the hypothalamic arcuate nucleus. In both structures, we observed a differential activation of Fos in females, depending on the level of buck sexual activity. Indeed, goats unexposed to males showed low levels of expression of Fos while those exposed to sexually inactive bucks showed an intermediate level of Fos expression. Finally, the highest level of Fos expression was found in females exposed to sexually active males. However, and contrary to our initial hypothesis, we were not able to find any specific activation of kisspeptin cells in the arcuate nucleus following the introduction of highly sexually active males. As a whole, these results demonstrate that the level of male sexual activity is a key factor to stimulate brain regions involved in the control of the gonadotrope axis in the context of the male effect in goats.

Sexually active bucks are efficient to stimulate female ovulatory activity during the anestrous season also under temperate latitudes

Goats are seasonal breeders and photoperiod is the main cue controlling the onset and offset of the breeding season. Nevertheless introducing a sexually active buck in a group of females during anestrous can stimulate their reproductive function and induce ovulation. This "male-effect" is very efficient under subtropical latitudes, when using sexually active males previously stimulated by a photoperiodic treatment. However, there is less evidence of its feasibility under temperate latitudes where the more important variation in day length could be responsible for a stronger inhibition of female sexual activity. The aim of this study was therefore to determine whether intense sexual activity can be induced in alpine bucks during the non-breeding season by a long-day treatment under temperate latitude and if these males could be used to produce an efficient male-effect. Bucks (n=21) were divided in two groups, one submitted to a photoperiodic treatment from November 1st to January 15th and then switched to natural photoperiod, while the other group remained entirely under the natural photoperiod. The ones submitted to this light treatment exhibit higher testicular volume and testosterone level 6 weeks after the end of the treatment. At the end of March, bucks were used to stimulate anestrous does (n=41) continuously for 15 days. We showed that (a) light treatment was efficient to induce an increase of sexual activity in bucks and (b) that the introduction of stimulated bucks among females induced a significantly higher proportion of ovulation in anestrous does than control bucks (86% vs 5%). Our results indicate that under temperate latitudes induction of ovulation in females during the anestrous season is feasible using bucks treated with long-days during winter.

Evaluation of hormone-free protocols based on the "male effect" for artificial insemination in lactating goats during seasonal anestrus

Goat estrous and ovulatory responses to the "male effect" were characterized to determine the time range over which fertile ovulations occur after buck exposure. The results were used to explore the efficacy of different hormone-free artificial insemination (AI) protocols aimed at diminishing the number of inseminations needed to optimize fertility. Adult bucks and does were exposed to artificially long days during winter and then exposed to a natural photoperiod before buck exposure (Day 0). Most goats (>70%) ovulated twice, developing a short cycle followed by a normal cycle over 13 days after buck exposure. Among them, 21% were in estrus at the short cycle and 94% at the normal cycle. This second ovulation occurred within 48 hours of Day 6 and was the target for AI protocols. In protocol A (n = 79), goats were inseminated 12 hours after estrus detection from Day 5 to Day 9. Up to six AI times over 4 days were needed to inseminate goats in estrus. Forty-nine percent of the inseminated goats kidded. In protocol B (n = 145), estrus detection started on Day 5. The earlier (group 1) and later (group 2) buck-marked goats received one single insemination at fixed times on Days 6.5 or 7 and 8, respectively; unmarked goats (group 3) were inseminated along with group 2. In protocol C (n = 153), goats were inseminated twice on Days 6.5 or 7 and 8 without needing to detect estrus. Goats induced to ovulate by hormonal treatment were used as the control (n = 319). Fertility was lower in protocol B than in protocol C and controls (47% vs. 58% and 65% kidding; P ≤ 0.05), whereas this was higher in buck-marked goats than in unmarked ones (64% vs. 33%; P ≤ 0.05). In protocol B, fertility can increase (>60%) when only goats coming into estrus are inseminated. The best kidding rate (∼70%) was achieved when does were inseminated within 24 hours of the LH surge. Protocols involving insemination on Day 7 instead of Day 6.5 led to more goats being inseminated during this favorable time.

Sexually active males prevent the display of seasonal anestrus in female goats

A well-defined season of sexual rest controlled by photoperiod is observed in female sheep and goats during spring and summer, delineating their "anestrous season"; bucks also decrease sexual activity at about the same time. Nutrition and/or socio-sexual stimuli play only secondary roles. However, the presence of sexually active males can reduce the length of seasonal anestrus. Whether it can also completely suppress anestrus has not been investigated. Here we tested this in goats in 3 experiments, using bucks rendered sexually active out of season by exposure to long days. The continuous presence of these males prevented goats to display seasonal anestrus: 12/14 females cycled the year round, vs. 0/13 and 0/11 for females with un-treated bucks or without bucks (experiment 1). When active bucks were removed, females immediately entered anestrus (7/7 stopped ovulating vs. 1/7 if maintained with active bucks; experiment 2). Finally, 7/7 anestrous does with bucks in sexual rest since 1.5months commenced cycling rapidly during mid-anestrous, when these bucks became sexually active following a treatment with artificial long days, vs. 0/7 with un-treated bucks or no bucks (experiment 3). The presence/withdrawal of active bucks had a highly significant effect in the three experiments (P≤0.002). Therefore, the presence of a mating opportunity can completely override the photoperiodic inhibition of reproduction of females throughout the anestrous season. Results suggest that we must re-evaluate the relative contributions of photoperiod vs. other external cues in controlling seasonal reproduction, thus offering new non-pharmaceutical ways for controlling out-of-season reproduction in small ruminants.

Importance of intense male sexual behavior for inducing the preovulatory LH surge and ovulation in seasonally anovulatory female goats

The present study was carried out to determine whether the presence of photostimulated sedated male goats could stimulate the LH preovulatory surge and ovulation in seasonal anestrous goats. Sexually experienced male goats were treated with artificial long days (16 hours light per day) from 1 November to 15 January to stimulate their sexual activity in March and April, corresponding to the natural sexual rest. A female group of goats (n=20) was exposed to non-sedated males who displayed an intense sexual behavior and provided strong odor (non-sedated group). Another female group of goats (n=20) was exposed to the photo-stimulated male goats, but these males were sedated with Xylazine 2% to prevent the expression of sexual behavior (sedated group). The sedated males also provided a strong odor. Females of both groups had full physical and visual contact with non-sedated or sedated males. In both groups, the males remained with females during 4 days. The LH preovulatory surge of 10 female goats per group was measured by determination of LH plasma concentrations in samples taken every 3 hours. In addition, in all goats, (n=20 by group), ovulation was determined by measuring plasma concentrations of progesterone. The proportion of female goats showing a preovulatory LH surge was higher in goats exposed to non-sedated (10/10) than in those exposed to sedated bucks (0/10; P<0.0001). Similarly, most of does in contact with non-sedated males ovulated (19/20), but none of those in contact with sedated males did so (0/20; P<0.0001). We conclude that the expression of an intense sexual behavior by male goats is necessary to induce LH preovulatory surge and ovulation in seasonally anovulatory goats.

Reducing exposure to long days from 75 to 30 days of extra-light treatment does not decrease the capacity of male goats to stimulate ovulatory activity in seasonally anovulatory females

The response of male goats exposed to different durations of long days (LD) during an extra-light treatment in autumn-winter, and their ability to induce ovulations in seasonally anovulatory goats were investigated in 2 experiments. In experiment 1, control males were exposed to natural photoperiod (n = 5), whereas 4 additional groups (n = 5/group) were exposed to 16 h of light per d during 75, 45, 30, or 15 d of LD. In the 4 groups, photoperiodic treatments ended on January 15th. Plasma concentrations of testosterone were determined in blood samples obtained once a week from October 15th to May 30th. The rise of testosterone levels occurred earlier in males from the 75-LD and 45-LD groups than in those from the 30-LD, 15-LD, and control groups (P < 0.05). In addition, the time during which levels of testosterone remained >5 ng/mL was longer in males from the 75-LD and 45-LD than in those from the 30-LD and 15-LD groups (P < 0.05). In experiment 2, a group of anovulatory goats (n = 13) was isolated from males, while 3 additional groups were put in contact during 15 d with males previously exposed to 75, 45, or 30 days of LD (n = 25, 27, and 26 females/group, respectively and n = 3 males per group). The proportion of goats that ovulated was higher in the 3 groups in contact with the photo-stimulated males (range: 88%-92%) than in the group isolated from them (0%; P < 0.05). The proportion of pregnant females did not differ between the 3 groups of does in contact with photo-stimulated males (range: 78%-92%; P > 0.05). We conclude that, in our experimental conditions, a photoperiodic treatment as short as 30 d of LD during autumn-winter, stimulated testosterone secretion of bucks during their period of sexual rest and rendered them able to induce ovulations in seasonal anestrous goats and to obtain pregnancies in these females.

Two or 24 h of daily contact with sexually active males results in different profiles of LH secretion that both lead to ovulation in anestrous goats

Two experiments were conducted to (a) determine whether sexually active males are able to stimulate the sexual activity of anestrous female goats when duration of contact is reduced to an intermittent contact shorter than 4 daily hours and (b) compare the pattern of secretion of LH when anestrous goats are exposed either permanently or intermittently to males. In the first experiment, 4 groups of anovulatory goats were exposed to sexually active males for 24, 4, 2, or 1 h/d during 15 consecutive days, whereas control females remained isolated. More than 89% of females in the groups exposed to the sexually active bucks ovulated, whereas only 5% did so in the control group (P < 0.001). However, the proportion of females ovulating before day 4 was greater in the 2-, 4-, or 24-h contact groups than in the control, whereas it did not differ between the control group and the 1-h contact group (P = 0.02, <0.001, <0.001 and 0.23, respectively). In the second experiment, 3 groups of anovulatory goats were exposed permanently (24 h/d) or intermittently (2 h/d) to bucks during 5 d or remained isolated. We found that pulsatility of luteinizing hormone (LH) increased in the intermittent and permanent contact groups after males were introduced to females (P = 0.05); this pulsatility of LH remained elevated in the permanent-contact group, whereas it decreased in the intermittent-contact group, once the male was removed (P = 0.32 and 0.05, respectively). We conclude that 1 or 2 daily hours of contact with sexually active males is sufficient to stimulate ovulatory activity in anovulatory goats; however, ovulation is obtained through a different pattern of secretion of LH.

Male goat vocalizations stimulate the estrous behavior and LH secretion in anestrous goats that have been previously exposed to bucks

We investigated whether live vocalizations emitted by bucks interacting with anestrous females stimulate secretion of LH, estrous behavior and ovulation in anestrous goats. In experiment 1, bucks rendered sexually active by exposure to long days followed by natural photoperiod were exposed in a light-proof-building to five anestrous females. Buck vocalizations were reproduced through a microphone-amplifier-loudspeaker system to an open pen where one group of goats (n=6) was exposed for 10 days to these live vocalizations. Another group of females (n=6) was isolated from males and vocalizations. The proportion of goats displaying estrous behavior was significantly higher in females exposed to buck vocalizations than in females isolated from males. The proportion of goats that ovulated did not differ between the 2 groups (exposed to males versus isolated). In experiment 2, female goats that either had previous contact with males (n=7), or no previous contact with males (n=7) were exposed to live buck vocalizations, reproduced as described in experiment 1, for 5 days. The number and amplitude of LH pulses did not differ between groups before exposition to buck vocalizations. Five days of exposure to male vocalizations significantly increased LH pulsatility only in females that had previous contact with males, while LH pulse amplitude was not modified. We concluded that live buck vocalizations can stimulate estrous behavior and LH secretion in goats if they have had previous contact with bucks.

Environmental and social cues can be used in combination to develop sustainable breeding techniques for goat reproduction in the subtropics

Goat breeds from subtropical latitudes show different annual reproductive cycles. Some of them display large seasonal variations in their annual breeding season, while others display a moderate seasonality or sexual activity all year round. This reproductive seasonality causes seasonality of milk, cheese and meat productions and, as a consequence, induces wide variation in producer incomes. To solve this problem and provide methods allowing producers to breed animals during the anestrous period and stabilize production all year round, it is necessary to have a deep knowledge of their annual sexual activity and to identify the environmental factors controlling the timing of the annual reproductive cycle. Then, it is possible to build on these knowledge sustainable breeding techniques adapted to the environmental, economic and social characteristics of the local breeding system. In this review, I will illustrate this strategy through the example of our experiments in subtropical goats. First, we determined the characteristics of the annual breeding season in both male and female goats. Second, we identified the photoperiod as the major environmental factor controlling the timing of this annual breeding season. Third, we used the photoperiod to stimulate indirectly the sexual behavior of does. Indeed, we used photoperiodic treatments to stimulate the sexual activity of bucks during the non-breeding season. These sexually active male goats were then used to induce and synchronize the estrous behavior and ovulatory activity of anestrous females in confined or grazing conditions by using the 'male effect'. Under subtropical conditions, these results constitute an original manner to control the reproductive activity of local goats using the photoperiod combined with the 'male effect.'

Lack of sexual experience does not reduce the responses of LH, estrus or fertility in anestrous goats exposed to sexually active males

We investigated whether LH secretion, estrous behavior and fertility would differ between sexually inexperienced and experienced anestrous goats exposed to the males. Male goats were rendered sexually active during the reproductive rest season by exposure to 2.5 months of artificial long days. Two groups of anovulatory sexually inexperienced and sexually experienced does were exposed to males during 15 days (n = 20 per group). LH pulsatility was determined every 15 min from 4h before to 8h after introducing males (Day 0). Estrous behavior was recorded twice daily. Pregnancy rates were determined on Day 50. Fertility was determined at parturition. Male sexual behavior was registered on days 1 and 2 during 1h. Before introducing the males, the number of LH pulses did not differ between groups. After introduction of the males, all females increased their LH pulsatility, but the number of pulses did not differ between sexually inexperienced and experienced goats. The proportion of females displaying estrous behavior with a high pregnancy rate and fertility did not differ between inexperienced and experienced goats. The sexual behavior of the males did not differ significantly between those interacting with sexually inexperienced or experienced goats. We conclude that goats can show substantial endocrine and reproductive responses to males, even in the absence of previous sexual experience, when sexually active bucks are used.

Reproductive performance is improved during seasonal anoestrus when female and male Murciano-Granadina goats receive melatonin implants and in Payoya goats when females are thus treated

This work investigates whether the reproductive performance of Mediterranean goats achieved using melatonin implants at around the spring equinox is affected by the protocol followed, i.e. implanting females only, males only, both sexes or neither sex. In a first experiment, Murciano-Granadina females (n = 419, 510 and 631 for three consecutive years) were divided into four groups: treated with melatonin (FM) and not treated with melatonin (FC), mounted by males treated with melatonin (MM) or not (MC). In a second experiment, performed during 2009, the same protocols were used with 635 Payoya females and the results compared with those obtained for the same year for the Murciano-Granadina breed. Fertility (percentage of goats kidding), litter size (number of kids born per female kidded) and productivity (number of kids per female in each mating group) were calculated. In the first experiment, better reproductive performances were obtained when females (overall fertility: 71.1% vs 57.0% for the FM and FC animals; productivity 1.37 ± 0.04 kids per female vs 1.12 ± 0.03 kids per female for the FM and FC animals; p < 0.01) or males (overall fertility: 65.9% vs 58.4 for the MM and MC animals; productivity 1.28 ± 0.03 kids per female vs 1.13 ± 0.04 kids per female for MM and MC groups, respectively; p < 0.01) were implanted with melatonin. Moreover, the interaction sex × melatonin treatment had a significant effect (p < 0.05) on productivity. In the second experiment, for the Murciano-Granadina breed, the greatest increase in the number of kids born per female was obtained when the females were treated with melatonin, in either the FM/MC or FM/MM protocols (0.54 extra kids and 0.53 extra kids per female, respectively) (p < 0.01). In the Payoya breed, the greatest increase was obtained using the FM/MC protocol (0.19 extra kids per female). Thus, improved reproductive performances are obtained when female Murciano-Granadina and Payoya goats are implanted with melatonin, although important differences in reproductive performance are seen between the breeds.

Progesterona plasmática de ovelhas submetidas ao efeito-macho e mantidas sob diferentes condições nutricionais

Dosou-se a concentração plasmática de progesterona (P4) em ovelhas Santa Inês (SI), Suffolk (SU) e Romney Marsh (RM) em anestro sazonal e submetidas ao efeito-macho, as quais receberam ou não suplementação alimentar. Machos vasectomizados foram introduzidos no grupo de fêmeas após um período prévio de isolamento de 60 dias, e amostras de sangue foram colhidas antes e após a introdução dos machos. Houve efeito (P<0,01) de período, raça, interação período x raça e interação suplementação x período x raça sobre a concentração de P4. Nas ovelhas SI ocorreu aumento (P<0,01) da concentração de P4 após a introdução do macho, indicando que houve aumento na atividade cíclica reprodutiva desse grupo. A suplementação, neste caso, potencializou este aumento. Nas ovelhas SU e RM não ocorreram modificações na concentração de P4 (P>0,01) após a introdução dos machos, nem houve efeito de suplementação. O efeito-macho foi eficaz em induzir a atividade reprodutiva durante o anestro sazonal em ovelhas SI, mas não em ovelhas SU e RM, e a associação dessa prática com a suplementação alimentar é recomendada para ovelhas da raça nativa SI.