Historical range expansion and biological changes of Sus scrofa corresponding to domestication and feralization

The natural diet composition of young piglets suggests an overlook of fibre and food structure in farmed suckling piglets

BACKGROUND

The often disappointing intake of creep feed by suckling piglets coincides with a limited ability to cope with challenges such as weaning diarrhoea. Investigating the dietary nutrient profile of piglets (Sus scrofa) in the wild may help to improve nutrition for farmed piglets. This study was conducted to analyse the stomach content of feral piglets and their farmed counterparts, and to compare them with the composition of commercial creep feeds. Forty feral piglets (4.6 ± 1.4 kg) living in a wild herd were tracked and legally hunted in the Bahía Samborombón (Buenos Aires, Argentina). Their gastric contents were collected for analysing macronutrients. Twenty-eight farmed suckling piglets of similar ages were sourced from a Dutch research farm, and their stomach contents were collected and pooled into fourteen samples with the same procedure for comparison. Additionally, the composition data of twenty-five commercial feeds was also collected.

RESULTS

A higher dry matter content was observed in the farmed piglets' stomachs (233 vs. 148 g/kg, P < 0.05). The gastric crude protein concentration was similar between both groups but the crude fat concentration was higher in the stomach of farmed animals (525 vs. 238 g/kg DM, P < 0.05), while feral piglets consumed more ash and fibre (P < 0.05). A similar concentration of non-fibrous carbohydrates (NFC) on metabolizable energy basis was observed by calculation through the NRC's guideline (P > 0.05). Within the fibre content, significantly greater concentrations of neutral detergent fiber (NDF), acid detergent fiber (ADF) and acid detergent lignin (ADL) were observed in the stomach of feral piglets than in those of farmed piglets (282 vs. 36 g/kg, 158 vs. 9 g/kg DM, 53 vs. 3 g/kg DM, respectively, P < 0.05). Similar protein concentrations were observed between the gastric content of feral piglets and creep feed, while significantly higher crude ash and crude fat concentrations were found in feral piglets' consumption (P < 0.05).

CONCLUSION

In conclusion, piglets in natural conditions consume much more fibre-from coarse plant material-compared to farmed piglets receiving creep feed. Although technical performance is distinctly different between nature and farm, it raises the question whether suckling piglets under farming conditions would benefit from a more fibrous and coarser creep feed.

Quantifying the ecological role of crocodiles: a 50-year review of metabolic requirements and nutrient contributions in northern Australia

The ecological roles of large predators are well recognized, but quantifying their functional impacts remains an active area of research. In this study, we examined the metabolic requirements and nutrient outputs of the estuarine crocodile population (Crocodylus porosus) in northern Australia over a 50-year period, during which the population increased from a few thousand to over 100 000 individuals. Bioenergetic modelling showed that during this period, the crocodile population's annual prey consumption increased from <20 kg km-2 in 1979 to approximately 180 kg km-2 in 2019. Further, the prey consumption increase was accompanied by a significant dietary shift from predominantly aquatic prey (approx. 65% in 1979) to a terrestrial-based diet (approx. 70% in 2019). A substantial portion of these terrestrial-derived nutrients was excreted into the water, significantly increasing the input rates of nitrogen (186-fold) and phosphorus (56-fold). The study shows that, despite being ectothermic, the high biomass of crocodiles within the environment generated nutrient inputs comparable to terrestrial endothermic predator populations. While crocodiles are apex predators, they are not considered to influence ecosystems in the same manner that large-bodied endothermic predators do. However, in the oligotrophic freshwater systems of northern Australia, the large volume of crocodile biomass is likely to impact the ecosystem through top-down and bottom-up processes.

Chromosome-Level Genome Assembly of the Meishan Pig and Insights into Its Domestication Mechanisms

Pigs are essential agricultural animals, and among the various breeds, the Meishan pig, a native breed of China, is renowned for its high reproductive performance. This breed has been introduced to many countries to enhance local pig breeding programs. However, there have been limited genomic and population genetics studies focusing on Meishan pigs. We created a chromosomal-level genomic assembly using high-depth PacBio sequencing and Illumina sequencing data collected from a Meishan pig. Additionally, we analyzed whole-genome sequencing (WGS) data from Chinese boars and Meishan pigs to identify domestication selection signals within the Meishan breed. The assembled genome of the Meishan pig (MSjxau) was found to be 2.45 Gb in size, with a scaffold length of 139.17 Mb. The quality value was 37.06, and the BUSCO score was 96.2%, indicating good completeness, continuity, and accuracy. We annotated transposable elements, segmental duplication, and genes in the MSjxau genome. By combining these data with 28 publicly available genomes, we provide a high-quality structural variants resource for pigs. Furthermore, we identified 716 selective sweep intervals between Chinese wild pigs and Meishan pigs, where the selected gene PGR may be linked to the high fertility observed in Meishan pigs. Our study offers valuable genomic and variation resources for pig breeding and identifies several genes associated with the domestication of the Meishan pig. This lays the groundwork for further investigation into the genetic mechanisms behind complex traits in pigs.

Motivation and Habits of a Wild Boar-Hunting Community

The wild boar (Sus scrofa) is a widespread ungulate, the populations of which have recently increased throughout most of its range. This increase has caused negative impacts on ecosystems, biodiversity, and society. Nowadays, the wild boar is considered both a valuable game and a pest. Wildlife managers need to know the habits and motivations of wild boar hunters, a key stakeholder group, for effectively managing this controversial mammal. We carried out face-to-face interviews with 134 wild boar hunters in the Evros Prefecture, in the Region of Eastern Macedonia and Thrace, northern Greece to determine their hunting habits and their motivation for hunting. Most hunters owned a hunting dog (84.3%), hunted in groups of eight to nine people for 48 days, traveled 60 km, stayed outdoors for 4 nights, and spent weekly EUR 61 on average in each hunting season. Two motivations for wild boar hunting were prominent among the hunters (assessed on a 5-point scale; 1 = strongly disagree to 5 = strongly agree): a strong recreation motivation (hunting as a recreational activity; mean score 4.159 ± 1.144 SD) and a considerable utility motivation (hunting for its use values; 3.404 ± 1.11). Both recreation and utility motivations were positively associated with the preference for further increases in wild boar populations. Sociodemographic characteristics and hunting habits variously affected motivations and preferred future population trends. The findings revealed specific habits and strong motivations among hunters. Such findings will be useful for designing and implementing education and outreach programs for informing hunters about the negative impacts of wild boars and the need for their control. The participation of hunters in the management process will be critical for its success.

Mapping the risk of exposure to Crimean-Congo haemorrhagic fever virus in the Iberian Peninsula using Eurasian wild boar (Sus scrofa) as a model

Crimean-Congo haemorrhagic fever (CCHF) virus (CCHFV) is a tick-borne zoonotic pathogen that can cause a lethal haemorrhagic disease in humans. Although the virus appears to be endemically established in the Iberian Peninsula, CCHF is an emerging disease in Spain. Clinical signs of CCHFV infection are mainly manifested in humans, but the virus replicates in several animal species. Understanding the determinants of CCHFV exposure risk from animal models is essential to predicting high-risk exposure hotspots for public health action. With this objective in mind, we designed a cross-sectional study of Eurasian wild boar (Sus scrofa) in Spain and Portugal. The study analysed 5,291 sera collected between 2006 and 2022 from 90 wild boar populations with a specific double-antigen ELISA to estimate CCHFV serum prevalence and identify the main determinants of exposure probability. To do so, we statistically modelled exposure risk with host- and environment-related predictors and spatially projected it at a 10 × 10 km square resolution at the scale of the Iberian Peninsula to map foci of infection risk. Fifty-seven (63.3 %) of the 90 populations had at least one seropositive animal, with seroprevalence ranging from 0.0 to 88.2 %. Anti-CCHFV antibodies were found in 1,026 of 5,291 wild boar (19.4 %; 95 % confidence interval: 18.3-20.5 %), with highest exposure rates in southwestern Iberia. The most relevant predictors of virus exposure risk were wild boar abundance, local rainfall regime, shrub cover, winter air temperature and soil temperature variation. The spatial projection of the best-fit model identified high-risk foci as occurring in most of western and southwestern Iberia and identified recently confirmed risk foci in eastern Spain. The results of the study demonstrate that serological surveys of CCHFV vector hosts are a powerful, robust and highly informative tool for public health authorities to take action to prevent human cases of CCHF in enzootic and emergency settings.

The Effect of the Wild Boar Hunting System on Agricultural Damages: The North-East of Italy as a Case Scenario

Hunting is a method commonly used in several European countries to reduce crop damages by wild boar Sus scrofa. However, results are still controversial and poorly treated. Using data on official claims (i.e., damages to crops) and wild boar local counts and hunting bags collected from 2019 to 2022, the purpose of this work was to evaluate the effect of the hunting system (divided into eradication and non-eradication areas) carried out in the north-east of Italy on the number of agricultural damages. The spatio-temporal distribution of wild boar hunting, density and damages as well as the effect of hunting, were evaluated through the hotspot analysis and the zero-inflated models, respectively. The results obtained revealed no clear spatial overlap among wild boar hunting, wild boar density and damages to agriculture in both the eradication and non-eradication areas. Moreover, the current level of harvesting did not significantly affect the number of agricultural damages. A multifaceted approach focused on the numeric control of the species based on accurate local counts and oriented towards more age classes in a similar percentage should be preferred to mitigate damages to cultivars.

Thermoregulation in the wild boar (Sus scrofa)

The wild boar (Sus scrofa) originates from warm islands but now inhabits large areas of the world, with Antarctica as the only continent not inhabited by this species. One might be tempted to think that its wide distribution results from increasing environmental temperatures. However, any effect of temperature is only indirect: Abundant availability of critical food resources can fully compensate the negative effects of cold winters on population growth. Here, we asked if temperature as a habitat factor is unimportant compared with other habitat indices, simply because wild boars are excellent thermoregulators. We found that the thermoneutral zone in summer was approximately 6-24 °C. In winter, the thermoneutral zone was lowered to 0-7 °C. The estimated increase in the heart rate and energy expenditure in the cold was less than 30% per 10 °C temperature decline. This relatively small increase of energy expenditure during cold exposure places the wild boar in the realm of arctic animals, such as the polar bear, whereas tropical mammals raise their energy expenditure several fold. The response of wild boars to high Ta was weak across all seasons. In the heat, wild boars avoid close contact to conspecifics and particularly use wallowing in mud or other wet substrates to cool and prevent hyperthermia. Wild boars also rely on daily cycles, especially of rhythms in subcutaneous temperature that enables them to cheaply build large core-shell gradients, which serve to lower heat loss. We argue it is predominantly this ability which allowed wild boars to inhabit most climatically diverse areas in the world.

Diet and stomach characteristics of feral piglets (Sus scrofa): Implications for farmed piglets

Evaluation of the diet of the pig (Sus scrofa) in natural settings may provide new views on diet optimization for growth and development of commercially raised piglets under farm conditions. A field study was conducted to gain insight in the diet and stomach characteristics of feral piglets. Forty animals (body weight: 4.6 ± 1.37 kg) were collected from the Bahía Samborombón (Buenos Aires, Argentina). Stomachs were weighed after storage in formalin and the particle size distribution of their contents was determined by wet sieving. Diet items present in their stomachs were classified and their proportional weight and relative abundance was calculated. Based on their dentition, 5, 16 and 19 piglets were approximately 1, 3-6 and 6-16 weeks of age respectively. Vegetable matter (mainly 'leaves and stems') was predominantly present in 39 animals. It represented on average 83 ± 36.4% of total stomach contents by weight. The stomachs of 12 piglets contained curd and represented on average 16 ± 35.1% by weight. Other diet items were less abundant or absent. The proportion of stomach particles retained were 24%, 13%, 22%, 13% and 28% for sieves with mesh sizes of 2000, 1000, 420, 210 and <210 µm respectively. For comparison, we used data of farmed piglets of similar age and fed a nutrient-dense, finely ground diet. Feral piglets' relative empty stomach weights increased with age (p < 0.050), whereas this was not the case for farmed piglets. Relative stomach contents weight increased significantly with age only for farmed piglets (p < 0.050). We infer from our data that feral suckling piglets consumed a variety of non-milk items, mainly consisting of vegetable material with a coarse particle size from their first week in life onwards. Their diet is associated with an enhanced stomach development compared to those of farmed piglets.

Understanding the impact of wild boar on the European wild rabbit and red-legged partridge populations using a diet metabarcoding approach

European wild rabbit (Oryctolagus cuniculus) and red-legged partridge (Alectoris rufa) are main small game species of conservation concern in Mediterranean ecosystems. To date, their presence in wild boar’s (Sus scrofa) diet and factors driving their consumption have been little investigated. A genetic metabarcoding approach was used on 80 wild boar faeces collected from four hunting estates devoted to small game hunting during two different seasons. Abundances of wild boar, rabbits and partridges were first estimated. Results showed DNA of seventeen chordate species. The highest frequency of occurrence (FO) corresponded to mammals and birds, with 77.6 and 22.3%, respectively. DNA of game species was detected in 39/71 (FO = 55.0%) samples, highlighting the presence of European wild rabbit in 27 (FO = 38.0%) and red-legged partridge in eight (FO = 11.3%). Dietary composition varied between seasons and estates, being rabbit the main responsible (explaining 35.26% and 39.45% of differences, respectively). Rabbit FO in the diet was positively related to the abundance of wild boar and rabbit density on the estate. It was greater in autumn and in estates where rabbits were hunted. Regarding red-legged partridge, a significant and positive relationship between its population density and its diet FO was observed, without significant differences between seasons or estates. Overall, our results suggest wild boar as an opportunistic species whose diet is largely determined by the relative availability of different food resources. Its ecological role concerning small game species in Mediterranean agroecosystems seems to be more related to consumption of carrion during the hunting season than to direct predation.

Introduced, Mixed, and Peripheral: Conservation of Mitochondrial-DNA Lineages in the Wild Boar (Sus scrofa L.) Population in the Urals

Translocations and introductions are important events that allow organisms to overcome natural barriers. The genetic background of colonization success and genetic consequences of the establishment of populations in new environments are of great interest for predicting species’ colonization success. The wild boar has been introduced into many parts of the world. We analyzed sequences of the mitochondrial-DNA control region in the wild boars introduced into the Ural region and compared them with sequences from founder populations (from Europe, the Caucasus, Central Asia, and the Far East). We found that the introduced population has high genetic diversity. Haplotypes from all the major phylogenetic clades were detected in the analyzed group of the animals from the Urals. In this group, no haplotypes identical to Far Eastern sequences were detectable despite a large number of founders from that region. The contribution of lineages originating from Eastern Europe was greater than expected from the proportions (%) of European and Asian animals in the founder populations. This is the first study on the genetic diversity and structure of a wild boar population of mixed origin at the northern periphery of this species’ geographical range.

The Boar War: Five Hot Factors Unleashing Boar Expansion and Related Emergency

The recent and ever-growing problem of boar (Sus scrofa forms including wild boar, hybrid and feral pig) expansion is a very complex issue in wildlife management. The damages caused to biodiversity and the economies are addressed in different ways by the various countries, but research is needed to shed light on the causal factors of this emergency before defining a useful collaborative management policy. In this review, we screened more than 280 references published between 1975–2022, identifying and dealing with five hot factors (climate change, human induced habitat modifications, predator regulation on the prey, hybridization with domestic forms, and transfaunation) that could account for the boar expansion and its niche invasion. We also discuss some issues arising from this boar emergency, such as epizootic and zoonotic diseases or the depression of biodiversity. Finally, we provide new insights for the research and the development of management policies.