Precocious puberty in male wild boars: a possible explanation for the dramatic population increase in Germany and Europe

Heavy Youngsters-Habitat and Climate Factors Lead to a Significant Increase in Body Weight of Wild Boar Females

As one of the most abundant game species in Europe, European wild boar (Sus scrofa) populations prove highly adaptable to cultivated landscapes. The ongoing process of climate change and the high agricultural yields seem to further optimize the living conditions for this species. In long-term reproduction monitoring, we collected data on the body weight of wild boar females. Over an 18-year period, the body weight of wild boar females increased continuously, then stopped and decreased. It was possible to detect differences between the body weights of animals from forest and agricultural areas. For these areas, differences in body weight development also led to a significant distinction in the onset of puberty. We conclude that, even in a highly cultivated landscape, forested areas provide habitat characteristics that may strongly influence reproduction. Second, with dominant agricultural areas in Germany, wild boar reproduction has been favored in recent decades.

An Approach for Investigating Sexual Maturity in Wild Boar Males: Testosterone and 17β-Estradiol Analysis

Simple Summary

Wild boar numbers have increased constantly over the last three decades, as have their related conflicts with modern society. For this reason, wild boars have become a frequent topic of discussion. This article describes and explains the concentrations of the two main sexual steroids, testosterone and estradiol, as well as our effort to define threshold levels to recognize the sexual maturation of wild boar males and differentiate between immature and adult boars. With the help of additional analyses on spermatozoa and morphological data, it was shown that prepubertal boars at 8 months of age could be clearly differentiated from postpubertal boars, showing significantly lower concentrations of hormones. Wild boar males older than 11 months of age, in contrast, presented hormonal values like adults. Before the completion of their first year, wild boars are physiologically able to reproduce and may take part in reproduction. The high hormonal concentrations at the end of the breeding season suggest that the mating period could last longer than usually supposed, shifting farrowing into the summer.

Abstract

Analyses of sexual steroid hormones in wild boars are rarely described. Testosterone (T) and 17β-estradiol (E2) concentrations are useful to recognize sexual maturation. As threshold values for this species are unknown, additional parameters are required. A total of 127 blood samples from wild boar males were collected to measure T and E2. Age and weight were recorded. Thirty-one epididymides were sampled too. Males were sorted into pre-and postpubertal groups based on the absence/presence of spermatozoa in epididymides and on morphological data following previous results. Forty-four males were prepubertal: the mean age and weight were 10 months and 23 kg, respectively. They showed no spermatozoa. The mean concentrations of T and E2 were 1.2 ± 1.2 ng/mL and 39.7 ± 120.3 pg/mL, respectively. Sixty-six males were postpubertal, twenty-nine of which presented spermatozoa. Their mean concentration of T was 7.6 ± 6.3 ng/mL and E2 was 664.3 ± 250.4 pg/mL. Seventeen samples could not be defined; the hormone concentrations between the two groups suggested a transitional phase consistent with puberty. Wild boars before 12 months of age had high hormone levels like older boars, indicating that they could attempt to reproduce. Hormones at the end of the mating season (January) were high so that reproduction could occur thereafter, shifting farrowing from spring to summer.

MeDIP-seq and RNA-seq analysis during porcine testis development reveals functional DMRs at the promoter of LDHC

Testis development requires tight regulation of gene expression programmed by epigenetic modifiers. However, their mechanism remains to be elucidated. Here, we investigated the genome-wide DNA methylation landscape in the Duroc and Meishan boar testes using methylated DNA immunoprecipitation sequencing (MeDIP-seq). We identified over 1100 promoter differential methylation genes (DMGs) before and after puberty, most of which are associated with testis development. Furthermore, we discovered that the expression of lactate dehydrogenase C (LDHC) gene during testis development is regulated by DNA methylation. The promoter of LDHC in pre-pubertal testes is substantially methylated, whereas considerably demethylated in post-pubertal testes. Artificial demethylation with the demethylating agent 5-Aza-CdR induced LDHC expression in immature Sertoli cells (SCs). Mechanistically, we confirmed the transcription factor SP1 was recruited to bind in hypomethylated differentially methylated regions (DMRs) in LDHC promoter, which upregulated the expression of LDHC. Functionally, we demonstrated that LDHC gene was activated in mature SCs (mSCs) and its overexpression significantly increases lactate secretion in SCs. In conclusion, our results highlight the function and regulation of dynamic DNA methylation in testis development.

Genetic Diversity of Porcine Circovirus Types 2 and 3 in Wild Boar in Italy

Simple Summary

Porcine circoviruses (PCVs) are major viral agents of farmed swine, causing relevant economic impact due to direct losses and control measures expenses. Wild boar may serve as a PCVs reservoir for the domestic pigs, thus threatening for production efficiency in pig farms. PCV infection in both domestic pigs and wild boar has been chiefly studied in Northern Italy, a densely populated area with a highly developed pork industry. However, data on circulation of PCV are scarce in other Italian areas. For the above reasons, along with the increasing sanitary relevance of wildlife as host of many livestock diseases, we carried out an epidemiological study to assess the prevalence and genetic characteristics of the PCVs circulating in wild boar in Basilicata region (Southern Italy), characterized by large forested areas with limited anthropic presence. A high prevalence was detected, suggesting that PCVs infection is endemic in the study population. These findings are of particular interest as the pig production system of the study area involves local breeds raised outdoor for the production of high-quality cured meat, thus having a high risk of being in contact with infected wild boar.

Abstract

Porcine circovirus (PCV) infection is associated with relevant economic impact to the pig industry. To date, four species of PCV (PCV1 to 4) have been identified but only PCV2 has been associated firmly with disease in pigs. The objective of this study was to assess the prevalence of PCV2 and PCV3 in the wild boar population in Basilicata region, Southern Italy, since this region is characterized by large forested and rural areas and the anthropic pressure is lower than in other Italian regions. Liver samples from 82 hunted wild boar were collected in 2021 from 3 different hunting districts. Sixty (73%, 95%CI: 63–82) samples tested positive for PCVs by quantitative PCR. In detail, 22 (27%, 95%CI: 18–37) were positive for PCV2, 58 (71%, 95%CI: 60–79) for PCV3, and 20 (24.4%, 95%CI 16–35) for both PCV2 and PCV3. On genome sequencing, different types and sub-types of PCV2 and PCV3 were identified, remarking a genetic diversity and hinting to a global circulation for the identified PCV strains. Overall, the high prevalence suggests that PCV2 and PCV3 infections are endemic in the wild boar population, posing risks for semi-intensive and free-range pig farming, typical of this region, due to contact with PCV-infected wild boar.

Fluctuations in serum steroid hormone concentrations and body mass during growth and sexual maturation in captive northern fur seals (Callorhinus ursinus)

Northern fur seals (Callorhinus ursinus) have a distinct life history pattern comprising annual terrestrial breeding and oceanic migration, and the physiological changes associated with these patterns are of particular interest for understanding their environmental adaptations. However, owing to their oceanic distribution, limited information is available on the reproductive physiology of wild individuals during the immature stage and the winter migration period. This study aimed to determine the relationships among the seasonal hormone profiles, body growth, age, and pregnancy using monthly serum samples collected over 3–5 years from two male and two female captive individuals during pubescence and sexual maturation. Small increases in the serum testosterone signaled puberty in males aged 3 and 4 years. Thereafter, males showed considerable increases in testosterone during breeding seasons, indicating sexual maturity. Immature female serum progesterone was maintained at low levels, but after pubescence, females showed an increase in serum progesterone in August, the month next to the peak of delivery, followed by a decrease. In non-pregnant females, progesterone did not increase significantly until the next breeding season, but in pregnant females, they increased again from February to March and then gradually decreased. Immature males increased body mass constantly and reached puberty when their body mass exceeded 20 kg, and they showed seasonal weight fluctuations after puberty. These results provide fundamental information for determining sexual maturity and pregnancy in this species based on sex steroid hormones and body mass measurements.