Nutrition level and season of birth do not modify puberty of Payoya goat kids

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.

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.

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.

Early weaning and high feeding level in post-weaning period did not impact milk production in Alpine dairy goats

The experiment reported in this Research Communication aimed to determine the combined effects of early weaning and post-weaning feeding level on growth, reproductive parameters and milk yield in Alpine goats. Sixty-four Alpine goat kids were weaned abruptly at either 12·2 (±1·40) kg (40 d of age, E) or 17·7 (±2·30) kg (60 d of age, No). After weaning, E and No goats were subjected to 2 feeding strategies (n = 16): ad libitum concentrate until 130 d of age and then 620 g DM/d/goat until 200 d of age (EC and NoC) or ad libitum concentrate until 200 d of age (EAL and NoAL). Goats were weighed twice a month until 200 d of age. Pregnancy rate and litter size were recorded. Daily milk yield was measured by milk meter during the first lactation. Up to 60 d of age, average daily gain (ADG) of E kids was significantly lower than No kids. From 60 to 130 d of age, ADG of the four treatments were not different. After 130 d of age, EC and NoC kids had lower ADG than EAL and NoAL kids. Pregnancy rates of EAL and NoAL goats were lower than those of EC and NoC. Milk yield was not modified by weaning weight or feeding management. Milk quality was not affected by any treatment. To conclude, the age at weaning as well as the feeding level after weaning did not negatively impact growth and milk yield. We hypothesise that the establishment of the lactation function is not impacted by rearing management. Hence, decreasing the age at weaning could be an interesting way to reduce the cost of the rearing period in goat kids.

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.

The timing of oestrus, the preovulatory LH surge and ovulation in Blanca Andaluza goats synchronised by intravaginal progestagen sponge treatment is modified by season but not by body condition score

The aim of this study was to determine whether a seasonal pattern of reproductive events is followed after synchronisation by intravaginal progestagen sponge treatment in female Blanca Andaluza goats, and whether the timing of these events is affected by body condition score (BCS). During seasonal anoestrus (March), and again during the breeding season (November), the same 32 does were distributed into four subgroups according to their BCS: ≤2.25, =2.50, =2.75, and ≥3.00 (n=8 in all cases). They were then synchronised using a commercial intravaginal sponge treatment. Every 4h over the 72h following sponge removal, oestrous activity, the LH concentration and each doe's number of follicles were followed by transrectal ultrasonography. The does synchronised during seasonal anoestrus produced more follicles than those synchronised during the breeding season (P<0.01). The time elapsed between sponge removal and the onset of oestrus, the LH surge and time of ovulation, was also shorter in these does (P<0.001). The BCS only modified the number of follicles present in the ovary just before ovulation; this number was significantly lower in the =2.50 BCS subgroup than in the other subgroups (P<0.05). The present results show that the time to ovulation, and all events around it, are modified by the season in which Blanca Andaluza does are synchronised, but not by BCS.

Influence of the male effect on the reproductive performance of female Payoya goats implanted with melatonin at the winter solstice

This research addressed the effect on reproductive performance of melatonin implants inserted at the winter solstice in Payoya goats. Female goats (n = 100) were divided into two experimental groups, one subjected and the other not subjected to the male effect. Half of each group was implanted with melatonin at the winter solstice; the remaining animals received no such hormone treatment. Oestrous activity, as detected by visual observation, was recorded daily using melatonin implanted bucks. Trans-rectal ultrasonography was used to estimate of time of ovulation. Corpus luteum activity was confirmed by plasma concentrations of progesterone greater than 0.5 ng/mL. Fecundity, fertility, prolificacy and productivity were calculated. Neither the male effect nor melatonin treatment alone influenced reproductive performance. The greater fecundity and fertility: 91.7% (P < 0.05) was obtained with melatonin implantation plus the male effect. Greater productivity occurred when melatonin was used (1.02 ± 0.10 compared with 0.76 ± 0.66 mean number of kids per female for melatonin and non-melatonin treated groups, respectively, P < 0.05). The present results show that the fertility of female Payoya goats implanted with melatonin at the winter solstice can be improved by subjecting females to the male effect. Moreover, productivity of does is enhanced when melatonin implants are used in comparison to productivity of non-treated females.