Maintenance of permanent sexual activity throughout the year in seasonal bucks using short photoperiodic cycles in open barns.

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).

Sexually active male goats stimulate the endocrine and sexual activities of other males in seasonal sexual rest through the "buck-to-buck effect".

Male goats rendered sexually active by exposure to a photoperiodic treatment are more efficient than untreated goats in stimulating LH secretion and ovulation in seasonally anestrous goats. This phenomenon is called the "male effect." Here, we determined whether sexually active bucks are able to stimulate the endocrine and sexual activities of other bucks in seasonal sexual rest through the phenomenon that we called the "buck-to-buck effect." We used bucks rendered sexually active (SA) during sexual rest by exposure to 2.5 mo of artificial long days (16 h of light per d) and untreated, sexually inactive (SI) bucks. In Experiment 1, we determined the short-term (21 d) LH and testosterone responses of sexually inactive bucks joined with a SA or SI buck. In Experiment 2, we determined the long-term (60 d) testosterone and sexual behavior responses of sexually inactive bucks joined with 2 SA or SI bucks. In Experiment 3, we determined the efficacy of bucks initially exposed to the buck-to-buck effect, the SABB bucks, to thereafter induce a "classical" male effect in seasonally anestrous goats. In Experiments 1 and 2, there was an interaction between time and groups in LH and testosterone plasma concentrations (P < 0.01). In Experiment 1, plasma LH concentrations were greater in bucks joined with a SA buck than in those joined with an SI buck (P < 0.05). In Experiments 1 and 2, testosterone concentrations were greater in bucks joined with SA bucks than in those joined with SI bucks (P < 0.05). In addition, in Experiment 2, the sexually inactive bucks joined with SA bucks displayed more nudging than those joined with SI bucks (P < 0.001). In Experiment 3, kidding rates did not differ between females joined with SA (34 of 40: 85%) or SABB bucks (32 of 40: 80%; P > 0.05). We concluded that the endocrine and sexual activities of bucks during sexual rest can be stimulated by SA bucks. In addition, SABB bucks are able to stimulate the reproductive activity of seasonally anestrous goats.

Review: Managing sheep and goats for sustainable high yield production.

This review discusses the most relevant aspects of nutritional, reproductive and health management, the three pillars of flock efficiency, production and sustainability regarding the intensification of production in sheep and goats. In small ruminants, reproductive management is dependent on seasonality, which in turn depends on breed and latitude. Nutrition represents the major cost for flocks and greatly affects their health, the quality of their products and their environmental impact. High-yielding sheep and goats have very high requirements and dietary intake, requiring nutrient-dense diets and sophisticated nutritional management that should always consider the strong interrelationships among nutrition, immunity, health, reproduction, housing and farm management. The reproductive pattern is to a great extent assisted by out-of-season breeding, facilitating genetic improvement schemes, and more recently by advanced reproductive technologies. Heath management aims to control or eradicate economic and zoonotic diseases, ensuring animal health and welfare, food safety and low ecosystem and environmental impacts in relation to chemical residues and pathogen circulation. In highly producing systems, nutrition, genetic and hazard factors assume a complex interrelationship. Genomic and management improvement research and technological innovation are the keys to sustain sheep and goat production in the future.

Nutritional supplementation improves the sexual response of bucks exposed to long days in semi-extensive management and their ability to stimulate reproduction in goats.

In confined management systems, well-nourished bucks rendered sexually active by exposure to long days are efficient in fertilizing out-of-season goats. However, underfeeding is common in semi-extensive management systems and may reduce the reproductive efficiency of bucks. The objective of the present study was to determine whether nutritional supplementation improved the sexual activity of bucks submitted to long days in semi-extensive management systems and their ability to stimulate the reproduction of goats in semi-extensive or confined conditions. In experiment 1, three groups of bucks were placed in different flocks and grazed daily with females for 7 h. Each day after grazing, males were separated from females and moved into open pens. One group did not receive any treatment (control group; n = 6). Two other groups were submitted to artificially long days from 15 November to 15 January. From 16 January, one group did not receive nutritional supplementation (long-day group; n = 5), whereas bucks from the other group each received 600 g of a commercial concentrate (long-day+supplementation group; n = 5). The fourth group was kept in confined conditions, exposed to long days and fed alfalfa hay (long-day confined group; n = 6). On 26 March, anovulatory goats from other flocks were assigned to four groups (n = 27 each) and confined separately in open pens. Three bucks of each group were housed with the females. Pregnancy rates were greater in the goats housed with the long-day group than those housed with the control group (P < 0.01). However, pregnancy rates did not differ between the long-day confined group (89%) and long-day+supplementation group (70%; P = 0.09), but these rates were greater than those from the long-day (37%) and control groups (0%; P < 0.05). In experiment 2, two groups of males (n = 3 each) were incorporated into two flocks under semi-extensive management and grazed daily with females for 7 h. One group of males did not receive any treatment (control group). The other group was submitted to long days and nutritional supplementation as in experiment 1 (long-day+supplementation group). Males remained with females during the whole study. The pregnancy rate was greater in the goats joined by males of the long-day+supplementation group (78%) than in those from the control group (0%; P < 0.001). We conclude that long days and nutritional supplementation improve the ability of bucks kept in semi-extensive management to stimulate reproduction of out-of-season goats in confined or semi-extensive management systems.

The continuous presence of ewes in estrus in spring influences testicular volume, testicular echogenicity and testosterone concentration, but not LH pulsatility in rams.

The continuous presence of active male small ruminants prevents seasonal anestrus in females, but evidence of the same mechanism operating from the females to the males is scarce. This study assessed the effects of the continuous presence of ewes in estrus in spring on ram sexual activity, testicular size and echogenicity, and LH and testosterone concentrations. On 1 March, 20 rams were assigned to two groups (n = 10 each): isolated (ISO) from other sheep, or stimulated (STI) by 12 ewes, which were separated from the rams by an openwork metal barrier, allowing contact between sexes. Each week, four ewes were induced into estrus by intravaginal sponges. Live weight, scrotal circumference, testicular width (TW) and length (TL) were recorded at the beginning and at the end of the experiment, and testicular volume (TV) was calculated; at the same time, testicular ultrasonography and color Doppler scanning were performed. Blood samples (March to May) were collected once per week for testosterone determinations, and at the end of the experiment, blood samples were collected for 6 h at 20-min intervals for LH analysis. Rams were exposed to four estrous ewes in a serving-capacity test. Scrotal circumference, TW and TL were higher in the STI than in the ISO rams (P < 0.05) in May, and TV was higher (P < 0.05) in the STI (391 ± 17 cm3) than in the ISO rams (354 ± 24 cm3). In ISO rams, the number of white pixels was higher (P < 0.01) in May (348 ± 74) than in March (94 ± 21) and differed significantly (P < 0.01) from that of the STI rams in May (160 ± 33). In ISO rams, the number of grey pixels was higher (P < 0.05) in May (107 ± 3) than it was in March (99 ± 1). Stimulated and ISO rams did not differ significantly in mean LH plasma concentrations (0.8 ± 0.5 v. 0.9 ± 0.4 ng/ml), LH pulses (2.1 ± 0.5 v. 2.2 ± 0.2) and amplitude (2.0 ± 0.4 v. 3.2 ± 0.7 ng/ml, respectively). Stimulated rams had significantly higher testosterone concentrations than ISO rams from April to the end of the experiment. Stimulated rams performed more (P < 0.05) mountings with intromission (3.0 ± 0.4) than did ISO rams (1.5 ± 0.5). In conclusion, after 3 months in the continuous presence of ewes in estrus in spring, rams had higher TV and some testicular echogenic parameters were modified than isolated rams. Although exposed rams also had higher levels of testosterone after 2 months in the presence of estrous ewes, their LH pulsatility at the end of the study was not modified.

Undernutrition reduces the body weight and testicular size of bucks exposed to long days but not their ability to stimulate reproduction of seasonally anestrous goats.

In semiarid conditions, feed is often scarce and variable with underfeeding being common; these factors can potentially induce fertility reductions in both sexes. Sexually active bucks are able to very efficiently fertilize out-of-season goats, but we do not know whether underfeeding would reduce the ability of bucks to fertilize goats during these periods. Two experiments were conducted to determine (i) testicular size and change of odor intensity of undernourished bucks exposed to long days and (ii) the ability of these bucks to stimulate reproductive activity in seasonally anestrous goats. In experiment 1, bucks (n = 7) were fed 1.5 times the normal maintenance requirements from September to May and formed the well-fed group. Another group of bucks (n = 7) were fed 0.5 times the maintenance requirements and formed the undernourished group. All bucks were subjected to artificially long days from 1 November to 15 January; this period was followed by a natural photoperiod until 30 May. Body weight, scrotal circumference and male odor intensity changes were determined every 2 weeks. In experiment 2, two groups of female goats (n = 26 each) were exposed to well-fed (n = 2) or undernourished bucks (n = 2) on 31 March. Ovulations and pregnancy rates were determined by transrectal ultrasonography. In experiment 1, a treatment by time interaction was detected for BW, scrotal circumference and odor intensity changes (P < 0.001). The BWs of well-fed bucks were greater than those of the undernourished bucks from October to May (P < 0.01), as were the scrotal circumferences from December to March (P < 0.05) and odor intensities from February to May (P < 0.05). In experiment 2, the proportions of females that ovulated at least once (100% v. 96%) or those that were diagnosed as pregnant (85% v. 77%; P > 0.05) did not differ significantly between the goats exposed to well-fed or undernourished bucks. The interval between the introduction of bucks and the onset of estrous behavior was shorter in goats exposed to well-fed bucks compared to the interval for those goats exposed to undernourished bucks (2.5 ± 0.2 v. 9.5 ± 0.6 days; P < 0.05). We conclude that undernourishment reduces the testicular size and odor intensity responses in bucks exposed to long days, but that undernourished bucks are still able to stimulate reproductive activity in seasonally anestrous goats, as is also the case for well-fed bucks.

Is it time to reconsider the relative weight of sociosexual relationships compared with photoperiod in the control of reproduction of small ruminant females?

In goats and sheep from the temperate and subtropical latitudes, the breeding season lasts from early autumn to late winter, whereas the anestrous season lasts from late winter to late summer. In prepubertal or postpartum females, the duration of the quiescent period depends mainly on the season of parturition and of nursing duration. In both situations, the ovulatory activity starts only during the breeding season. Photoperiod has been generally considered as a major regulator of all these periods of reproductive activity/inactivity in female sheep and goats (ie puberty, seasonal anestrus, postpartum anestrus). In particular, regarding seasonal anestrus, the sociosexual interactions between males and females have been considered to have only a modulatory role, limited to few weeks preceding the onset or after the offset of the breeding season. Nonetheless, we recently showed that the use of sexually active males plays a crucial role to trigger ovulatory and estrous activities during the anestrous season and also in prepubertal and postpartum females. In fact, in females exposed to sexually active males, puberty is strikingly advanced in comparison with females exposed to sexually inactive castrated males or to isolated females (6 mo vs 7.5 mo). Most females (>85%) exposed during the anestrous season to sexually active males ovulated, whereas a low proportion of them ovulated when in contact with sexually inactive males (<10%). Interestingly, the presence of these sexually active males allows females to ovulate all the year round and prevents the seasonal decrease of LH plasma concentrations in ovariectomized females treated with an estradiol implant. Finally, the presence of sexually active males triggers ovulation in postpartum anestrous females nursing their offspring. All these findings show that sexually active males can play an important role to reduce anestrous periods. We need, therefore, to reconsider the relative weight of sociosexual relationships, compared with photoperiod, in the management of reproduction of goat does and ewes.

Male effect using photostimulated bucks and nutritional supplementation advance puberty in goats under semi-extensive management.

Well-nourished spring-born female goats reach puberty in the autumn of the same year. Contrastingly, undernourished spring-born females reach puberty in the autumn of the following year. Therefore, in this study, we reared female goats (undernourished) under semi-extensive management and determined whether the introduction of photostimulated, sexually active males, advances puberty in these females, and whether nutritional supplementation increases the proportion of kidding females. Goats were born on March 30 and weaned at 2 months of age. Then, they grazed natural vegetation from 10:00 to 18:00 each day. Starting in December, two groups did not receive feed supplementation after grazing, whereas two other groups received 600 g daily supplements of a commercial concentrate. In April, one non-supplemented (n = 10) and other supplemented groups (n = 11) were moved indoors and kept in separate pens, where they were joined with sexually active bucks (n = 1 per group). Males were rotated daily between groups for 7 days. Other non-supplemented (n = 8) and supplemented groups (n = 11) were not joined with males. Most of the female goats under study reached puberty (70-100%). However, in supplemented and non-supplemented groups joined with males, puberty commenced much earlier (April) than in those non-exposed to males (September) (P < 0.001). The proportion of pregnant goats did not differ between groups joined with males (P > 0.05), but the proportion of goats that kidded was higher in supplemented (7/11) than in non-supplemented goats (2/10) (P < 0.05). In conclusion, in spring-born goats, the male effect using sexually active males advanced puberty, and nutritional supplementation increased the proportion of kidding goats in females reared under semi-extensive management.

Presence of a sexually active goat buck enhances ovulation occurrence in seasonally anestrous does after ovulation and luteolysis induction in hormonally-treated goats in seasonal anestrus.

In seasonally anestrous goat does, ovulations can be induced by combining a treatment regimen including progestagen, eCG and prostaglandins. Nonetheless, ovulations occur only once and then does return to a seasonally anestrous state. This study was performed to determine whether the presence of a sexually active buck can stimulate a second ovulation after induced luteolysis using prostaglandins following the first ovulation. Three groups of seasonally anestrous does were treated to induce ovulations using an intra-vaginally inserted sponge containing a progestin combined with eCG and prostaglandin administrations. Goats that had ovulations were treated with a prostaglandin 11 days after progestin sponge removal. After the prostaglandin injection, does continued to be isolated from bucks (n = 8), were penned with a control buck (n = 9), or were penned with a sexually active buck (n = 10). The proportion of goats having ovulations after imposing the ovulation-induction protocol was greater than 80% and did not differ among treatment groups (P >  0.05). The proportion of does having ovulations after injecting prostaglandins was greater when does were penned with a sexually active buck (8/10) than does penned with a control buck (0/9) or that were isolated from bucks (0/8; P < 0.05). It is concluded that in seasonally anestrous goat does induced to have ovulations using a hormonal treatment regimen, the presence of a sexually active buck can induce a second ovulation when there is an induced luteolysis.

Continuous presence of females in estrus does not prevent seasonal inhibition of LH and androgen concentrations in bucks.

In male goats, being in permanent visual contact with females in estrus does not prevent seasonal variation in certain endocrine hormone levels and sexual activities. In this study, we tested whether continuous and full contact with females in estrus prevented seasonal endocrinological variation in bucks. In 1 experiment (Exp. 1), we verified that the sudden introduction of goats in estrus increased the plasma concentrations of androgen in bucks during the nonbreeding season under our experimental conditions. In another experiment (Exp. 2), we tested the ability of estrous goats to prevent seasonal inhibition of LH and androgen secretions in bucks kept in permanent and full contact with them. In Exp. 1, 3 groups of bucks (n = 5 in each group) were isolated from females from the months of July to January. On January 27, one group continued being isolated from females; a second group was exposed to ovariectomized, untreated goats; and a third group was exposed to ovariectomized goats with induced estrus. Plasma androgen concentrations were determined every 2 h from 8 h before to 8 h after the introduction of females. The introduction of estrus-induced goats significantly increased androgen concentrations, which were higher than in the isolated bucks, as well as in those exposed to untreated goats (P < 0.05). In Exp. 2 (n = 5 per group), one group of bucks was isolated from females from October to July, whereas two other groups remained in contact with ovariectomized goats, either untreated or regularly induced to estrus. In the three groups of bucks, plasma concentrations of LH were determined once during the months of October, February, March, and June, whereas androgen concentrations were determined weekly from October to July. The mean plasma LH and androgen concentrations were low and did not differ among the groups of bucks during the normal seasonal period of sexual inactivity (P > 0.05). We conclude that full contact and sexual interactions with estrus-induced goats failed to stop the seasonality of LH and androgen plasma concentrations of bucks, although bucks could respond to the introduction of females by acute increases in plasma LH and androgen.

Light-induced sexually active rams prevent the seasonal inhibition of luteinizing-hormone in ovariectomized estradiol-implanted ewes.

The effect of the continuous presence of sexually active Rasa Aragonesa rams on the plasma luteinizing-hormone (LH) concentrations of ewes was studied from November to May. Light-treated rams were rendered sexually active (SA rams) by exposure to 2 months of artificially long days (16 h light/8 h dark) in one of two groups from either 1 November (SAR1, n = 3) or 1 December (SAR2, n = 3). Rams (n = 6) in a Control group were kept under the natural photoperiod. Thirty ewes were ovariectomized in September and implanted with a subcutaneous implant (l = 15 mm) that contained estradiol-17ß. One group of ewes (SAR; n = 10) was housed with control rams from 1 October to 15 February before being housed with SAR1 rams from 16 February to 31 March, and with SAR2 rams from 1 April to 31 May. A second group of ewes (C; n = 10) remained with control rams throughout the experiment, and a third group was kept isolated from rams throughout the experiment (ISO; n = 10). Blood samples were collected weekly from November to May, and plasma LH concentrations were measured. In the breeding season (November-February), plasma LH concentrations of ewes did not differ significantly between groups (SAR: 2.00 ±â€¯0.34; C: 1.88 ±â€¯0.16; ISO: 1.67 ±â€¯0.51 ng/ml). From March to May (seasonal anestrus), however, LH plasma concentrations decreased in the C and ISO groups (1.30 ±â€¯0.20 and 0.48 ±â€¯0.04 ng/ml, respectively), but remained at the same level as in the breeding season in the SAR group (2.30 ±â€¯0.17 ng/ml; P < 0.001). Significant differences (P < 0.01) between groups were observed from March onwards: LH concentrations were highest in SAR ewes (P < 0.001) and lowest in the ISO ewes. In conclusion, the continuous presence of sexually active rams prevented the seasonal decrease in plasma LH concentrations, probably by preventing the seasonal negative feedback of estradiol on LH secretion.

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.

Progesterone doses of 5, 3 or 1 mg do not prevent short ovulatory cycles in goats exposed to photo-stimulated bucks.

The aim of this study was to determine whether lower doses than 25 mg of progesterone reduce the frequency of short ovulatory cycles in seasonal anestrous goats exposed to sexually active bucks. Females from the control group were given an im dose of 2 mL olive oil (n = 9). Females from the experimental groups were given an im dose of 1 mg (n = 15), 3 mg (n = 16), 5 mg (n = 15) or 25 mg (n = 16) of progesterone diluted in 2 mL olive oil, 48 h prior exposition to bucks (n = 1 per group). Males were daily switched among groups, and they remained with goats during 21 days. The proportion of goats that ovulated was high (≥87%), and was not different among groups (P > 0.05). In contrast, the proportion of goats that displayed short ovulatory cycles differed among groups (P < 0.05). Indeed, the proportion of goats displaying short ovulatory cycles was lower in those treated with 25 mg (12%) than in those from the control (78%), 1 mg (85%), 3 mg (50%), or 5 mg (71%) groups (P < 0.05), but there were no differences among these last four groups (P > 0.05). Finally, the percentage of kidding females (≥40%) and the number of kids born per female (≥1.4) did not differ among groups (P > 0.05). In conclusion, an im dose of 25 mg of progesterone was more effective than 5, 3 or 1 mg to avoid the short ovulatory cycles in seasonal anestrous goats exposed to the male effect.

Photoperiod-treated bucks are equal to melatonin-treated bucks for inducing reproductive behaviour and physiological functions via the "male effect" in Mediterranean goats.

The aim of this study was to examine whether photoperiod-treated bucks have the same capacity as melatonin-treated bucks to induce reproductive responses in female goats during the spring. On 10 April, 38 anoestrous does were placed with: 1) photoperiod-treated bucks (additional light hours for 83 days from the end of the previous November; PHOTO; n = 12); 2) bucks treated with exogenous melatonin at the beginning of March (MEL; n = 13); and 3) bucks that received no treatments (CONTROL; n = 13). The bucks' sexual behaviour was assessed for 10 days, and doe oestrous behaviour was recorded for the next 32 days by checking for harness marks. Ovulation was confirmed from plasma progesterone concentration (measured twice per week) and ovulation rate was assessed by transrectal ultrasonography. Fecundity, fertility, prolificacy and productivity were also determined. The percentage of does in the PHOTO, MEL and CONTROL group: 1) having ovulations was 92%, 100% and 38% respectively; 2) expressing behavioural oestrous associated with ovulation was 92%, 100% and 31%; and 3) that became pregnant was 75%, 69% and 23%, respectively. The kids produced per doe were 1.08 ± 0.23, 1.15 ± 0.25 and 0.31 ± 0.17 for the PHOTO, MEL, and CONTROL groups, respectively with there being no differences between the PHOTO and MEL groups, however, there was a difference (P < 0.05) between PHOTO/MEL and CONTROL groups. Thus, imposing a stimulatory lighting regimen during the preceding winter period is as efficient as using subcutaneous melatonin implants in stimulating reproductive behaviours and physiological functions of bucks.

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.

Extensive management conditions do not modify the frequency of short ovulatory cycles in progesterone-treated does exposed to sexually active males.

Most goats exposed to males in confined conditions have short ovulatory cycles. The frequency of these cycles can be reduced with a progesterone treatment prior to the introduction of males. The objective of this study was to determine whether extensive management conditions modify the frequency of short ovulatory cycles in progesterone-treated does exposed to photostimulated males. One group of does remained in extensive management conditions and grazed daily from 10:00 to 18:00 h; two other groups were confined separately in shaded pens, and fed alfalfa hay. In March, females from the grazing group (n = 45; grazing-P4 group) and those from one confined group (n = 45; confined-P4 group) were treated with 25 mg of progesterone by intra-muscular injections 48 h before joining with photostimulated males (n = 3 per group). The other confined group did not receive the progesterone treatment and was exposed to two photostimulated males (n = 25; confined-control group). Does were exposed to males for 45 consecutive days. Determination of whether ovulations occurre were made by quantifying plasma progesterone concentrations after introduction of males. The proportion of does that had ovulations at least once was not different between groups (≥98%; P > 0.05). The proportion of does that had short ovulatory cycles differed between groups (P < 0.001), and this proportion was greater in the confined-control group (76%) than in confined-P4 (27%) and grazing-P4 groups (25%; P < 0.001). It is concluded that extensive management conditions do not modify the frequency of short ovulatory cycles in progesterone-treated does exposed to the photostimulated males.

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.

Extended day length in late winter/early spring, with a return to natural day length of shorter duration, increased plasma testosterone and sexual performance in rams with or without melatonin implants.

Sixteen rams were used to quantify the effects of long days, imposed during late winter/early spring, with or without exogenous melatonin, on plasma testosterone concentrations and ram serving capacity. Rams were assigned to two groups: photoperiod-treated rams (Artificial Photoperiod, AP; n = 8), exposed to 2 months of long days (16 hr of light/day) between 22 December and 22 February, and control rams (Natural Photoperiod, NP; n = 8). At the end of the long-day period, AP rams were returned to the natural photoperiod, and each ram in the two groups either did (+M) or did not (-M) receive three subcutaneous melatonin implants. Four groups were created as follows: AP+M (n = 4), AP-M (n = 4), NP+M (n = 4) and NP-M (n = 4). Thirty days after of the onset of photoperiodic treatment, AP rams (13.5 ± 2.8 ng/ml) had significantly (p < .05) lower testosterone levels than NP rams (36.7 ± 1.0), and similar differences were not apparent at the end of the photoperiod treatment. A month later, AP rams (24.3 ± 7.9) had higher (p < .10) testosterone levels than NP rams (13.1 ± 5.0), with no effect of melatonin treatment. Fifty days after melatonin implantations, rams were exposed for 20 min to three oestrous ewes. AP rams (2.50 ± 0.42) exhibited significantly (p < .05) more serves than did NP rams (1.11 ± 0.39), and melatonin treatment had no significant effect; however, the interaction between treatments was significant. Time to first serve was significantly (p < .05) shorter in AP (2.30 ± 1.20 min) than it was in NP rams (5.58 ± 0.68 min). In conclusion, exposure to 2 months of long days in late winter/early spring, with a return to natural day length of shorter duration, increased plasma testosterone concentrations and sexual performance in rams with or without exogenous melatonin. This particular management is an option if a non-hormonal reproductive strategy is scheduled; yet, if the use of exogenous hormones is feasible, melatonin implants increase the mating efficiency of rams.