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Context: In subtropical latitudes, most goats are managed in semi-extensive management systems, eating only available vegetation. Underfeeding is common during the dry season and may reduce the endocrine and sexual activities of male goats. Aims: The aim of the study was to determine plasma testosterone concentrations, sexual behaviour and sperm production of male goats kept in a semi-extensive management system for 12 months, from March to February. Methods: Control males were placed indoors and were well nourished (n = 5). Experimental males were placed in a flock and grazed daily with females for 7 h, eating only natural vegetation (n = 5). Experimental males were fitted with an apron to prevent mating during the study. Plasma testosterone concentrations were determined every 2 weeks. Sexual behaviour and sperm production were determined in May and June (beginning of breeding season), August and October (middle of season), and November and December (end of season). Key results: Plasma testosterone concentrations were higher (P < 0.05) in control than experimental males in June and from August to December. The percentage of males refusing to ejaculate was lower (P < 0.05) in control than experimental males throughout the study. Total number of spermatozoa per ejaculate was higher (P < 0.05) in control than experimental males in May, June, November and December. Sperm progressive motility was higher (P < 0.05) in control than experimental males in May and June and from October to December. Conclusions: The results indicate that male goats in a semi-extensive management system have lower plasma testosterone concentrations, sexual behaviour, and sperm quantitative and qualitative production than those in a confined management system. Implications: Nutritional supplementation may improve the endocrine and sexual activity of male goats in semi-extensive management systems. During the dry season (early autumn-late spring) in subtropical semi-extensive management systems, food availability decreases markedly, leading to undernutrition of male goats. We demonstrate that this undernutrition reduces sexual behaviour and sperm production during the breeding season (early summer–late autumn). This study indicates that nutritional supplementation may improve the sexual activity of male goats kept under semi-extensive management. [ABSTRACT FROM AUTHOR]

Background. Anestrous goats can cycle and become pregnant after the introduction of sexually active bucks, but some of them become anestrus probably because they have been fertilized and early embryonic death occurred or because they have not been fertilized and become refractory to the stimulation of bucks. Objective. Determine whether goats that were mated by bucks become anestrus probably because of an early embryonic death or refractoriness to buck stimulation. Methodology. Vasectomized (n = 2) and intact (n = 2) bucks were rendered sexually active by exposure to artificially long days (16 h of light per day) followed by natural variations of photoperiod. Bucks were introduced into two groups of anestrous goats (n = 15 each) and remained with them for 53 days. Estrous behavior, ovulation and pregnancy rate were determined. Results. All goats came into estrus, ovulated and were mated by bucks at least once during the study. The proportions of females that displayed estrus with or without ovulation did not differ between the two groups within 9 days after the introduction of bucks. However, the proportion of goats that came into estrus with or without ovulation was greater in goats mated by vasectomized bucks from 20 to 28 and from 50 to 53 days after introducing the bucks (P < 0.05). Finally, the proportion of goats that ovulated after the introduction of the bucks, but later returned to anestrus did not differ in goats mated by vasectomized or intact bucks (14% vs 33%; P > 0.05). Implications. These results indicate that in nonpregnant goats, refractoriness to the continuous presence of the same bucks may explain at least in part, the return to anestrus of most goats that stop cycling after an initial sexual response to the introduction of bucks. Conclusion. Nonpregnant goats mated by sexually active bucks become in anestrus, probably because they become refractory to the presence of the same males.

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. • In seasonal female goats, puberty occurs only during the breeding season. • In well-nourished spring-born goats, puberty occurs around 8 months of age. • In undernourished spring-born goats, puberty occurs around 1.5 years of age. • Sexually active bucks induce puberty around 1 year of age. • In females, nutritional supplementation increases kidding rates. [ABSTRACT FROM AUTHOR]

Abstract 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. Highlights • Most of the seasonal anestrous goats exposed to males display short ovulatory cycles. • These short ovulatory cycles are reduced in goats receiving 25 mg of progesterone. • Progesterone doses of 5, 3 or 1 mg do not prevent these short ovulatory cycles. [ABSTRACT FROM AUTHOR]

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.’

In seasonally anovulatory goats, daily contact with photostimulated bucks for 15 days stimulates ovulations in most females. In this study, we determined whether ovulation could be induced in goats exposed to photostimulated bucks for less than 15 days. Bucks were rendered sexually active during the nonbreeding season by exposure to 2.5 months of long days from November 1. The control group of females was exposed to one photostimulated buck for 15 days (n = 12). Other three experimental groups were exposed to males (n = 1 per group) for 1, 5, or 10 days (n = 14 or 15 females per group). Ovulations were determined by measurement of daily plasma progesterone concentrations during 17 days. All females from the control and experimental groups ovulated at least once during the experiment (P > 0.05). Furthermore, the proportions of goats that displayed a short luteal phase followed by a new ovulation, or a normal luteal phase after being in contact with males, did not differ between groups depending on the duration of time of contact with the photostimulated males (P > 0.05). In contrast, the proportions of females that displayed a short luteal phase followed by anovulation were greater in goats in contact with males for 1 day than in those in contact with males for 10 and 15 days (P < 0.05), whereas they did not differ from females exposed to males for 5 days (P > 0.05). We conclude that 1 day of contact with sexually active males is long enough to stimulate the ovulatory activity in seasonally anovulatory goats. However, a significantly higher proportion of females exposed to males for 1 day did not ovulate again after showing a short luteal phase. [ABSTRACT FROM AUTHOR]

Some breeds of goats originating from or adapted to subtropical latitudes display seasonal variations of their annual rhythm of reproduction. The reproductive seasonality causes a seasonal production of goat-derived products affecting producers, goats’ meat and milk industry and consumers. A good knowledge of the annual rhythm of reproduction, as well as the identification of the major environmental cues controlling this rhythm in both males and females, is necessary to draw new and sustainable techniques to induce a synchronized reproductive activity outside the natural breeding season and therefore to increase the out-of-season availability of the goat-derived products. This knowledge allows to control caprine reproduction without the use of exogenous hormones, and to develop techniques adapted to the environmental, economic and social characteristics of the breeding systems. Thus, in this review we will describe how photoperiodic treatments can be used to induce the sexual activity of male goats during the period of sexual rest. Then, we will describe how these photo-stimulated males were used to induce and synchronize the sexual activity of anestrous goats maintained in intensive or extensive management conditions by means of the male effect. In subtropical latitudes, the use of the male effect performed by using photo-stimulated bucks constitutes an original and sustainable way to control goats’ reproduction. [ABSTRACT FROM AUTHOR]

Abstract: The objective was to determine whether refractoriness to short and long days were involved in the end and onset of the breeding season, respectively, in goats adapted to subtropical latitudes. Ovariectomized does given a subcutaneous implant constantly releasing estradiol-l7 β (OVX+E) were used in two experiments. Plasma LH concentrations were determined twice weekly. In Experiment 1, the control group remained in an open-shed pen (natural day length and ambient temperature). Two experimental groups were placed in light-proof buildings (with natural temperature variations). One group was exposed to natural simulated increasing days (winter to spring), whereas the other was exposed to a winter solstice photoperiod (10 h of light) from December 21 to April 28. In Experiment 2, the control group remained under natural day length and ambient temperature. One experimental group was exposed to natural simulated decreasing days (summer to autumn), whereas the other group was exposed to a summer solstice photoperiod (14 h of light) from June 21 to October 20. In Experiment 1, the breeding season was not prolonged in does maintained in the winter solstice day length. Mean dates of decrease in LH secretion (end of the breeding season) did not differ significantly between does exposed to natural (February 3 ± 5 d) or natural simulated photoperiod (January 26 ± 14 d) and those exposed to constant short days of winter solstice (February 4 ± 10 d). In Experiment 2, the onset of the breeding season was not delayed in does maintained in the summer solstice day length. Mean dates of increase in LH secretion (onset of the breeding season) did not differ significantly between does exposed to natural (September 7 ± 8 d) or natural simulated photoperiod (September 18 ± 10 d) and those exposed to constant long days photoperiod of summer solstice (September 24 ± 4 d). In goats adapted to a subtropical environment, we concluded that: 1) the end of breeding season was due to refractoriness to short days, and not the inhibitory effect of increasing day length; and 2) the onset of the breeding season was due to refractoriness to long days, and not a stimulatory effect of decreasing day length. [Copyright &y& Elsevier]

Abstract: The objective of this study was to determine whether reproductive seasonality of local well-fed female goats from subtropical Mexico (26°N) can be controlled by photoperiod. The control group (n =12) remained in an open pen under natural photoperiod variations. The two experimental groups (n =8 each) were placed in light-proof rooms and exposed for 2 yr to alternations of 3 months of long days and 3 months of short days. One group was first exposed to long days, Group 1, and the other one to short days, Group 2. Blood samples were obtained twice a week to determine ovulation status by progesterone plasma concentrations. Goats from the control group displayed a seasonality of ovulations. The mean (±SEM) dates of the onset and end of the ovulations were September 10±5 d and February 16±4 d, respectively. In contrast, in both experimental groups, ovulations were modified (P <0.05) by the photoperiodic treatments such that ovulations started and ended during short and long days, respectively. In Groups 1 and 2, ovulations started 67±2 and 66±2 d (P >0.05), respectively, after the transfer from long to short days. In contrast, the timing of the cessation of ovulations after the transfer from short to long days differed (P <0.05) between groups (19±3 and 31±3 d for Groups 1 and 2, respectively). Local female goats from subtropical Mexico are, therefore, sensitive to photoperiodic changes that they are exposed to at this latitude and this environmental cue may control the timing of the breeding season in natural conditions. [Copyright &y& Elsevier]

Abstract: The objective of this study was to determine the importance of male sexual behavior in stimulating LH secretion in anovulatory female goats. Two groups of females (n =10 per group) were each exposed to a buck in sexual rest and submitted to natural daylength. In one group, the buck was awake, whereas in the other group, it was sedated to prevent its sexual behavior. Two other groups of goats (n =10 per group) were exposed to sexually active bucks that had been exposed to 2.5 months of long days. In one group, the buck was awake, and in the other group, it was sedated. LH secretion was determined every 15 min from 4 h before introducing the bucks to 8 h after, then every 15 min again from 20 to 24 h after introducing the bucks. The bucks submitted to natural daylength did not stimulate LH secretion (P >0.05), whether they were sedated or not. In contrast, both the awake and the sedated light-treated bucks induced an increase (P <0.05) of LH pulsatility in the first 4 h following their introduction. However, pulsatility remained elevated until 24 h in the females exposed to the light-treated awake buck, whereas in the group with the light-treated sedated buck, pulsatility diminished (P <0.05) after the first 4 h of stimulation by the buck. In conclusion, the sexual behavior of males contributes to the maintenance of a high LH pulsatility up to 24 h after introduction into a group of anovulatory goats. [Copyright &y& Elsevier]

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. [ABSTRACT FROM AUTHOR]