Four hours of daily contact with sexually active males is sufficient to induce fertile ovulation in anestrous goats

The study was conducted on two consecutive years to determine whether ovulatory activity can be induced in anovulatory goats by exposing them to sexually active bucks for 4, 8, 12 or 16 h per day during 15 consecutive days. In experiment 1, females remained continuously in the experimental pens where they were in contact with males. One group remained isolated from males (controls) and four other groups were exposed to sexually active males for 4, 8, 12 or 16 h per day. In experiment 2, females were taken away to “resting” pens free of male odours between the periods of contact with bucks. They were allocated to 5 groups as in experiment 1. Ovulations were determined by progesterone plasma levels and transrectal ultrasonography. Pregnancy was determined by abdominal ultrasonography. In both experiments, more than 90% of females exposed to the bucks had at least one ovulation during the whole experiment whereas only 11 or 0% (experiments 1 and 2, respectively) did so in the control group (P < 0.001). Furthermore, the proportion of females ovulating did not differ among groups depending on duration of contact with bucks (P > 0.05). In both experiments, pregnancy rates were not affected by the daily duration of contact with males (P > 0.05). To conclude, 4 h of daily contact with sexually active males is sufficient to stimulate ovulatory activity in anovulatory goats and this effect is not due to the presence of olfactory cues from the males remaining in the pens.     

Major plant communities of warm North American deserts

Abstract. A syntaxonomic study of the major plant communities in neotropical North American deserts (Sonoran, Mojave and Baja California Deserts) is presented. The field method of the Braun-Blanquet approach was combined with a numerical syntaxonomical analysis (cluster analysis and principal coordinate ordination). 21 associations are described for the first time: Ambrosio chenopodifoliae-Larreetum tridentatae, Acamptopappo sphaerocephali-Larreetum tridentatae, Hymenocleo monogyrae-Baccharidetum glutinosae, Bergerocacto emoryi-Agavetum shawii, Burseretum hindsianomicrophyllae, Cercidio microphylli-Carnegieetum giganteae, Bursero microphyllae-Cyrtocarpetum edulis, Hymenocleo salsolae-Daleetum spinosae, Echinocereo engelmannii-Agavetum deserti, Euphorbio californicae-Fouquierietum diguetii, Fouquierio splendentis-Larreetum tridentatae, Agavo cerulatae-Idrietum columnaris, Mascagnio macropterae-Lysilometum candidae, Maytenetum phyllanthoidis, Opuntio basilaris-Larreetum tridentatae, Prosopidetum torreyanae, Roso minutifoliae-Aesculetum parryi, Opuntio taponae-Agavetum subcerulatae, Tidestromio oblongifoliae-Atriplicetum hymenelytrae, Eurotio lanatae-Larreetum tridentatae and Yucco validae-Fouquierietum diguetii. Some associations include subassociations. Ecological, biogeographical and floristic bioclimatic data are given for each association.     

Shrubland formations and associations in mediterranean-desert transitional zones of northwestern Baja California

The area between Ensenada and EI Rosario (Baja California, Mexico) has long been considered as a transitional zone in which two great ecoclimatic regions (Mediterranean and Tropical-Desert) overlap. The floristic and biotypical diversity of this area was evaluated by analyzing its shrubland formations from a phytosociological point of view. This phytosociological study, carried out according to the Braun-Blanquet method and supported by cluster analysis, describes sixteen shrubland associations from Northwestern Baja California.Floristic diversity of the transitional zone was evaluated using two indices, endemic value (EV) and endemic community value (ECV), which are related to the degree of endemism in the flora and plant associations. The phytosociological analysis showed that the high number of shrubland associations found in this area reflected its transitional character. The closer the associations are to the transitional zone, the higher their biotypical and floristic diversity.Abbreviations ADE Adenostoma fasciculatum - AES Fraxinus trifoliata-Aesculus parryi - BER Bergerocactus emoryi-Agave shawii - DES Echinocereus engelmannii-Agave deserti - ENC Viguiera deltoidea-Encelia asperifolia - EUR Eurotia lanata-Yucca schidigera - FOU Agave cerulata-Fouquieria columnaris - FRA Atriplex julacea-Frankenia palmeri - HYM Baccharis glutinosa-Hymenoclea monogyra - KEC Clematis lasiantha-Keckiella antirrhinoides - LAR Ambrosia chenopodifolia-Larrea tridentata - LYC Ephedra californica-Lycium brevipes - MAH Malosma laurina-Heteromeles arbutifolia - MUN Salvia munzii-Artemisia californica - ROS Rosa minutifolia-Aesculus parryi - SAL Salvia apiana-Viguiera laciniata     

Positive correlation between the body weight of anestrous goats and their response to the male effect with sexually active bucks

In the present study, we analyzed the results of two years of response to the male effect in seasonally anestrous goats to investigate whether the activation of female reproductive activity by the male effect is related to the body weight of the females. Seventy-nine adult female Mexican mixed breed goats were used. The anestrous females were exposed during 15 days to sexually active males, and were classified into three categories according to their mean body weight +/-SD (42 +/- 9 kg) (Light: < or = 33 kg, n = 19; Medium: 34-50 kg, n = 46; Heavy: > or = 51 kg, n = 14). More than 98% of the goats from the Medium and Heavy groups showed at least one estrus behavior within the first 15 days following the introduction of the bucks, versus only 63% of the females from the Light group (P < 0.01). The interval between the introduction of the males and the onset of estrus behavior was longer in the females of the Light and Medium groups (4.2 +/- 0.8 and 3.3 +/- 0.3 days) than in the females of the Heavy group (2.0 +/- 0.2 days; P < 0.03). Also, body weight was negatively correlated with latency to first estrus (Spearman r = -0.57; P < 0.001). These results are in agreement with the hypothesis that the ability of anestrous goats to respond to the male effect is positively influenced by their body weight.     

Evidence of low within‐pair genetic relatedness in a relict population of Thorn‐tailed Rayadito despite long‐term isolation

Investigating whether mating patterns are biased in relation to kinship in isolated populations can provide a better understanding of the occurrence of inbreeding avoidance mechanisms in wild populations. Here, we report on the genetic relatedness (r) among breeding pairs in a relict population of Thorn‐tailed Rayadito (Aphrastura spinicauda) in north‐central Chile that has experienced a long‐term history of isolation. We used simulations based on 8 years of data to assess whether mating is random with respect to relatedness. We found that mean and median population values of pair relatedness tended to be lower than randomly generated values, suggesting that mating is not random with respect to kinship. We hypothesize that female‐biased dispersal is the main mechanism reducing the likelihood of mating among kin, and that the proportion of related pairs (i.e., r > 0.125) in the study population (25%) would presumably be higher in the absence of sex‐biased dispersal. The occurrence of other mechanisms such as extra‐pair copulations, delayed breeding, and active inbreeding avoidance through kin discrimination cannot be dismissed and require further study.     

Abolition of the seasonal release of luteinizing hormone and testosterone in Alpine male goats (Capra hircus) by short photoperiodic cycles.

This study was performed to determine whether rapid alternation between long and short days abolished seasonal variations in the activity of the hypothalamo-pituitary-testis axis observed normally in Alpine and Saanen male goats during the year. Three groups of 6 males were used: group 1 remained in open sheds under the natural annual change in daylength from 16 h of light (long day) to 8 h of light (short day). Group 2 was exposed to 1 month of long days alternated with 1 month of short days; and group 3 to 2 months of long days alternated with 2 months of short days. In group 1, blood samples were taken in December, February and June; in groups 2 and 3, samples were obtained once during short and long days for the melatonin assay. For luteinizing hormone and testosterone determinations monthly samples from group 1 were obtained from September to August while, in groups 2 and 3, blood samples were taken on 4 occasions during long and short days. Weekly blood samples were taken from all groups during the whole of the experiment to measure prolactin and testosterone concentrations. Melatonin profiles indicated that secretion by the pineal gland of male goats from the treated groups adapted to rapid changes in daylength: duration of nocturnal secretion was close to that of the dark period. Treated goats were also able to transduce this signal adequately and always responded to long days by increasing their prolactin concentration (mean +/- s.e.m.; group 2: 62.4 +/- 6.8 ng/ml; group 3: 102.3 +/- 15.7 ng/ml) and to short days with a decrease in prolactin concentrations (35.0 +/- 3.6 and 46.1 +/- 9.5 ng/ml, respectively). In the treated groups, luteinizing hormone pulse frequency varied with day length. In group 2, it was higher in long days (1.1 +/- 0.3 pulses in 8 hours) than in short days (0.7 +/- 0.3) while, in group 3, this frequency was higher in short days (1.9 +/- 0.3) than in long days (0.5 +/- 0.2). Testosterone secretion also varied with daylength; in group 2, the testosterone concentrations were maximum during long days (5.8 +/- 1.4 ng/ml) while in group 3 the maximum testosterone concentrations occurred during short days (6.4 +/- 1.2 ng/ml). These results lead to the conclusion that rapid alternation of long and short days either attenuated (group 3) or prevented (group 2) seasonal changes in the activity of the hypothalamo-pituitary axis.(ABSTRACT TRUNCATED AT 400 WORDS)     

Prepartum peripherally-induced hyposmia does not reduce postpartum anoestrus duration in nursing goats

Parturient goats rapidly develop exclusive nursing of their own litter that relies on olfactory recognition of the young. They also show a period of postpartum anoestrus whose duration depends on the presence of the kid. In cattle, maternal selectivity is one of the factors that delays the recovery of sexual activity. To investigate the possible influence of maternal selectivity on the duration of postpartum anoestrus in goats, we compared the recovery of estrus behavior by daily estrus detection with an active buck in intact and selective nursing goats (n = 24) with that of dams rendered non-selective by peripheral hyposmia with ZnSO4 (n = 18). Postpartum anoestrus duration was shorter in intact (68+/-7 days) than in hyposmic mothers (93+/-7 days; P < 0.05). However, the cycles of normal duration were less frequent in intact goats (P = 0.03). We conclude that in nursing goats, preventing the establishment of selective nursing by prepartum peripheral hyposmia does not reduce postpartum anoestrus duration. Our results suggest that daily exposure to the buck may result in an earlier recovery of ovarian activity in intact mothers.     

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.'