animals Communication Sexual Allometric Monomorphism in Araucan Pig from Colombia: Preliminary Results Arcesio Salamanca-Carreño 1 , Jordi Jordana-Vidal 2 , René Alejandro Crosby-Granados 1 , José Norberto Arias-Landazábal 1 and Pere M. Parés-Casanova 3, * 1 Grupo de Investigaciones los Araucos, Facultad de Medicina Veterinaria y Zootecnia, Universidad Cooperativa de Colombia, Arauca 810001, Colombia; asaca_65@yahoo.es (A.S.-C.); racrosbyg@yahoo.com (R.A.C.-G.); arias.landazabal@campusucc.edu.co (J.N.A.-L.) 2 Departament de Ciència Animal i dels Aliments, Universitat Autònoma de Barcelona, 08193 Bellaterra, Catalonia, Spain; jordi.jordana@uab.es 3 Departament de Ciència Animal, ETSEA, Universitat de Lleida, 25198 Lleida, Catalonia, Spain * Correspondence: peremiquelp@ca.udl.cat  Received: 31 August 2020; Accepted: 22 September 2020; Published: 28 September 2020  Simple Summary: Breed morphological profiling is the first step towards the conservation of local genetic resources, and data obtained from different approaches improve knowledge on them. Morphometric measurements performed on animals are important tools in the assessment of growth and body development as they make it possible to perform quantitative analysis. This study aimed to evaluate the allometric growth of the Araucan pig breed, a creole breed from Arauca, East Colombia, locally known as “Sabaneros”. Little is known about the production, economic importance, and geographical distribution of these animals. Knowledge on the genetics, morphology, growth potential, and yield characteristics of a breed is essential to establish a rational production system. Results showed that in Araucan pigs, sexual differences do not increase with body size. Abstract: This study aimed to evaluate the allometric growth of the Araucan pig breed, a creole breed from Arauca, East Colombia, locally known as “Sabaneros”, in relation to different quantitative traits and considering genders separately. To do this, a total of 31 male and 27 female Araucan pigs, ranging from 4 to 48 months of age, were studied in order to evaluate their growth patterns, using a multivariate approach. Animals belonged to different farms (“fincas”) of the Department of Arauca, Colombia. From each individual, 10 quantitative traits were obtained: face width, croup height, croup length, croup width, tail base height, hock height, loin height, cannon length, and length and width of ear. Our results, which must be interpreted as preliminary, showed that the Araucan pig is allometrically monomorphic as sexual differences do not increase with body size. We suggest that although males and females have evidently different reproductive roles, during growth they shift the allocation of energy to structures linked to environmental adaptation rather than those linked to reproduction. Keywords: creole breeds; multivariate allometry; relative growth; size sexual dimorphism; sexual selection 1. Introduction Breed morphological profiling is the first step towards the conservation of local genetic resources, and data obtained from different approaches improve knowledge on them [1]. Morphometric measurements performed on animals are important tools in the assessment of growth and body development as they make it possible to perform quantitative analysis. Animals 2020, 10, 1763; doi:10.3390/ani10101763 www.mdpi.com/journal/animals Animals 2020, 10, 1763 2 of 7 In animals, body measurements give significant information on morphological structure and development abilities, representing also the most influential factors on determining the most appropriate animals for a desired efficiency [2,3]. In animals, size contributes to body structure, harmony, and balance, but also to physiological characteristics and to mechanisms for adaptation to the environment [4,5]. Various physiological and pathological conditions, as well as different environmental and management conditions, can influence the size of the animals. Allometric growth studies examine the relative growth of a body component relative to a collection of other components, being an effective manner to study their development [6–8]. Morphometric measurements performed on animals provide additional information that is useful for determining phenotypic and genetic trends of growth of animals over the years [9]. Broadly, allometry has been suggested as having an influential impact on sexual shape dimorphism [10]. Iberoamerica has a great number of animals completely adapted to local conditions whose production is sustainable and ecological in all its phases, and whose product has a high nutritional value [11]. Known as “Creoles”, the pigs were not introduced to Colombia until the 16th century [9,12]. There they underwent hundreds of years of natural selection on the basis of adaptation to local environmental characteristics [13,14], which included survival and reproduction in geographical areas of tropical climates [11]. Over the past few decades, awareness has been raised about the importance of preserving animal genetic resources, although research initiatives are not yet totally widespread to most of the American continent [11,15]. This study aimed to evaluate the allometric growth of the Araucan pig breed, a local Colombian breed, in relation to different quantitative traits and considering genders separately. To the authors’ knowledge, this is the first time this topic has been analyzed for this population, although it has been done for other Creole pigs [9]. Araucan pigs are believed to have descended from pigs first brought from Spain during the 15th century and were selected for adaptation to the local conditions [14–16]. Locally known as “Sabaneros”, they are managed under extensive conditions in the Araucan plains of East Colombia, receiving scanty care and thriving semi-wildly on the savannah. Pigs are permanently exposed to environmental disturbances and irregular food supply. Little is known about their production, economic importance, and exact geographical distribution, which deserves special attention from the scientific community. The comprehension of this extensive production system involves the conservation of the environment and respect and welfare of the animals and also the farmer (“llanero”). 2. Materials and Methods 2.1. Area of Study Arauca is a department of Colombia located on the Orinoco Basin of Colombia (the “Llanos Orientales”) in the extreme east, bordering Venezuela. Its territory covers an area of 23,818 km2 . It is an ecosystem that is characterized by a plateau (Figure 1). The region is located between the Arauca and Casanare rivers. Seventy-five percent of the land is flat. Over the year, the temperature typically varies from 72 ◦ F to 97 ◦ F and is rarely below 69 ◦ F or above 102 ◦ F. This huge area receives low touristic impact, and waste dumped by multinational companies is its main threat. Animals 2020, 10, 1763 3 of 7 Animals 2020, 10, x 3 of 7 Figure Figure 1. Arauca 1. Arauca departmentlocated department located in in the the“Llanos “LlanosOrientales” Orientales”of Colombia. of Colombia. 2.2. Sample 2.2. Sample A total A total of 31ofmale 31 male andand2727 femaleAraucan female Araucan pigs, pigs, ranging rangingfrom from4 to 48 48 4 to months of age, months werewere of age, studied. studied. Male and female pigs were not subjected to castration. Animals belonged to different farms (“fincas”) Male and female pigs were not subjected to castration. Animals belonged to different farms (“fincas”) of the Department of Arauca, East Colombia, and were managed in the extensive traditional way. of the Department of Arauca, East Colombia, and were managed in the extensive traditional way. Environmental conditions and possible management differences between herds were identical. From Environmental conditions each individual, and possible 10 quantitative traits management were obtained:differences face width, between herds croup height, were croup identical. length, croupFrom each width, individual, tail base height, hock height, loin height, cannon length, and length and width of ear, followingcroup 10 quantitative traits were obtained: face width, croup height, croup length, width, tail base standard height, hock procedures height, loin height, cannon length, and length and width of ear, following [2,17,18]. standard procedures [2,17,18]. 2.3. Allometry 2.3. Allometry Allometry was evaluated using Jolicoeur’s multivariate allometric coefficient. Jolicoeur’s Allometryrepresents coefficient the coefficient was evaluated using(loading) of each Jolicoeur’s morphometricallometric multivariate variable forcoefficient. first axis of principal Jolicoeur’s component analysis (PCA) divided by 1/(√N), where N is the number of variables, coefficient represents the coefficient (loading) of each morphometric variable for first or appropriately axis of principal quoted [19]. PCA was performed from√a variance–covariance matrix. The first axis of the PCA component analysis (PCA) divided by 1/( N), where N is the number of variables, or appropriately quoted [19]. PCA was performed from a variance–covariance matrix. The first axis of the PCA contains most of the variability, and if all coefficients (loadings) of the morphometric variables for this axis are Animals 2020, 10, 1763 4 of 7 Animals 2020, 10, x 4 of 7 contains positive, most it can beofinterpreted the variability, as a and if all coefficients generalized (loadings) body size. In orderoftothe morphometric test variables for whether dimorphism increases this axis are positive, it can be interpreted as a generalized body size. In order to test whether with body size, a canonical discriminant analysis was performed to obtain the scores of individuals of dimorphism increases with body size, a canonical discriminant analysis was performed to obtain the the two sexes in a discriminant axis. Afterwards, following similar works [20], an ANCOVA based on scores of individuals of the two sexes in a discriminant axis. Afterwards, following similar works these scores was used to test the differences between sexes and the interaction with the generalized [20], an ANCOVA based on these scores was used to test the differences between sexes and the body size (first interaction PCA with theaxis). Statistical generalized bodyanalysis was size (first done PCA with axis). PAST v. Statistical 2.17c software analysis with pPAST was done [21]. values less than v. 0.05 2.17cwere considered software as statistically [21]. p values significant. less than 0.05 were considered as statistically significant. 3. Results 3. Results The first The firstPCA PCAaxis, axis, which representedthe which represented thegeneralized generalized sizesize asloadings as all all loadings appeared appeared positivepositive (Figure 2), explained 85.47% of the variability. Results of the ANCOVA showed an (Figure 2), explained 85.47% of the variability. Results of the ANCOVA showed an interaction between interaction thebetween the morphometric morphometric differentiation differentiation of the of the sexes sexes (first axis(first axis of discriminant of discriminant function) function) and theand the generalized generalized body size (first PCA axis). This result demonstrated that the morphometric body size (first PCA axis). This result demonstrated that the morphometric traits increased with traits increased with increasing age (Table 1) with no statistical differences between genders (p = 0.534) increasing age (Table 1) with no statistical differences between genders (p = 0.534) (Figure 3). (Figure 3). Figure Figure 2. 2. Coefficients(loadings) Coefficients (loadings) of ofthe themorphometric morphometric variables for first variables principal for first component, principal which which component, explained 85.47% of the variability in individuals of both sexes of Araucan pig (n = 58). As all loadings explained 85.47% of the variability in individuals of both sexes of Araucan pig (n = 58). As all loadings were were positive,they positive, theycan canbebe interpreted interpreted asasa ageneralized generalizedbody size.size. body Thoracic circumference Thoracic (PT), body circumference (PT), body length (LCO), withers height (ALC), sternum height (ALES), head length (LCA) and width (ACA), length (LCO), withers height (ALC), sternum height (ALES), head length (LCA) and width (ACA), ear ear length (LORE) and width (AORE), hindlimb cannon perimeter (PCAP), knee circumference length (LORE) and width (AORE), hindlimb cannon perimeter (PCAP), knee circumference (PRO), and (PRO), and hock height (ACO). hock height (ACO). Table Table 1. ANCOVAofofthe 1. ANCOVA thescores scores for for male male(n(n==31) and 31) female and (n =(n female 27)=individuals and age 27) individuals andof age Araucan of Araucan pigs, using the generalized body size (first axis of the principal component analysis, PC1) as a pigs, using the generalized body size (first axis of the principal component analysis, PC1) as a covariate. covariate. Sum of Effect Effect Sum of Squares Degrees Degrees of of Freedom MeanMean Squares F p F p Sex Squares 0.0550 Freedom1 Squares 0.05500 0.9831 0.0397 Age Sex 1.29760.0550 1 7 0.05500 0.18537 0.9831 3.31320.0397 0.0001 Sex x Age * Age −1.74221.2976 7 7 0.18537 −0.24889 3.3132 −4.44850.0001 0.4627 Residual Sex * Age 2.3499−1.7422 7 42 −0.24889 0.05594 −4.4485 0.4627 Residual 2.3499 * sex by 42age interaction. 0.05594 * sex by age interaction. Animals 2020, 10, 1763 5 of 7 Animals 2020, 10, x 5 of 7 Figure Figure 3. Relationship between 3. Relationship between thethescores scoresof canonical variate of canonical analysis variate (CV1) and analysis the generalized (CV1) size and the generalized size(first (firstprincipal principalcomponent component PC1) PC1)in individuals of both in individuals sexessexes of both of Araucan pig (31 of Araucan pigmales, ●, and 27 (31 males, , and 27 females, females, +). +). There There wereno were nostatistical statistical differences differencesbetween between genders genders(p =(p0.534). = 0.534). 4. Discussion 4. Discussion Morphometry Morphometry can can helpininthe help thecharacterization characterization ofofanimal animal breeds breedsas well as the as well asdefinition of their the definition of their use [2]. These measurements are influenced by the development of bones as well as deposition of use [2]. These measurements are influenced by the development of bones as well as deposition of muscle and fat. Measurements that are mainly linked to bone growth include face width and cannon muscle and fat. Measurements that are mainly linked to bone growth include face width and cannon length, as well as hock height. Measurements linked to soft tissue (muscle and fat) deposition are length, croup asand well asheights. loin hock height. Measurements linked to soft tissue (muscle and fat) deposition are croup and loin heights. Our preliminary results showed that sexual dimorphism of Araucan pigs does not increase with Our size body preliminary (i.e., they results show a showed monomorphicthat sexual dimorphism allometry). In the earlyofstages Araucan pigs does not of development, increase males and with body size (i.e., females they similar are more show athan monomorphic allometry). in the late stages, at least inInthe the early range studied stages(4ofto development, 48 months). We males and suggest femalesthat arealthough males and more similar thanfemales in thehave latedifferent stages, at reproductive least in the roles, during studied growth range (4 both to 48shift months). the allocation We suggest of energy to that although structures males more related and females havetodifferent adaptation than to reproduction. reproductive Thus,growth roles, during in late both shiftstages (48 months), the allocation the individuals of energy of the two to structures moresexes are morphometrically related to adaptation than similar. An investment Thus, to reproduction. of in males in increasing size would be only needed if it would provide advantages during fights with late stages (48 months), the individuals of the two sexes are morphometrically similar. An investment other males, and possibly during courtship and mating, but as herds are maintained in open herds, of males in increasing size would be only needed if it would provide advantages during fights with they remain very isolated from neighbor groups and territoriality is not necessary. Similar allometries otherformales, and possibly both genders within aduring courtship breed, but differingand mating, between but have breeds, as herds beenare maintained obtained by otherinauthors open herds, theyfor remain very isolated from other swine creole breeds [9]. neighbor groups and territoriality is not necessary. Similar allometries for both As genders within the sample a is size breed, but differing relatively scarce andbetween unbalanced breeds, have to according been obtained the sex and age bygroups, other authors there for otheris swine a major creole flaw breeds [9]. in the experimental design, so the results cannot be conclusive and need to be interpreted As the sample as a preliminary study. size is relatively Anyway, scarce our preliminary and unbalanced results should according to the sexbe and takenageinto accountthere is groups, when developing management and conservation programs for the breed. a major flaw in the experimental design, so the results cannot be conclusive and need to be interpreted as a Author preliminary study. Anyway, Contributions: our preliminary Formal analysis, results P.M.P.-C. and should A.S.-C.; be takenA.S.-C., investigation, into account when R.A.C.-G., developing J.N.A.-L.; methodology P.M.P.-C.; writing-review and editing, management and conservation programs for the breed. P.M.P.-C., J.J.-V., A.S.-C. All authors have read and agreed to the published version of the manuscript. Author Contributions: Formal analysis, P.M.P.-C. and A.S.-C.; investigation, A.S.-C., R.A.C.-G., J.N.A.-L.; methodology P.M.P.-C.; writing—review and editing, P.M.P.-C., J.J.-V., A.S.-C. All authors have read and agreed to the published version of the manuscript. Animals 2020, 10, 1763 6 of 7 Funding: This research was funded by a research grant from Research Committee-CONADI (ID 2863) of the Cooperative University of Colombia. Acknowledgments: Authors acknowledge the auxiliary students who helped for the data collection, as well as ranchers for their immense patience during the field work. 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