Breed and non-genetic risk factors associated with the prevalence of subclinical mastitis in livestock systems of Arauca, Colombian orinoquia.

Subclinical Mastitis (SCM) is caused by several factors associated with the interaction of the individual cow, cow management, and the environment. The aim of this study was to assess the breed and non-genetic risk factors on the prevalence of SCM in cows from the dual-purpose livestock system on the floodplain of Arauca, Colombian Orinoquia. Milk samples were taken from the individual mammary quarters of 481 cows representing 28 different farms where the electrical conductivity (EC) test applied. To determine the factors associated with SCM, a multiple logistic regression analysis was used. The response variable was the SCM presence (1), or absence (0) obtained with the EC test. Breed was included as a genetic risk factor, and as non- genetic risk factors: number of cows in production, daily milk production, lactation month, cow age, climatic period, body condition, and calving number. The factors that were significantly associated with the SCM presence were body condition, climatic period, and breed (p < 0.05). Odds ratio (OR) analysis of significant effects indicates that for each unit increase in body condition, the OR of having animals with SCM is reduced by 71%. In the dry period the OR of animals with SCM increases by 150% compared to the rainy period. Composite breeds reduce the OR of SCM animals by 73%, compared with Indicus-predominance animals. In this study, the occurrence of SCM in extensive management systems in Arauca, Colombian Orinoquia, is determined by the risk factors of breed, climatic period, and body condition.

Early Cannon Development in Females of the "Sanmartinero" Creole Bovine Breed.

The variation in the dimensions of the body of living beings in relation to their size, function, or shape is known as allometry. Allometry studies allow the analysis of the function of body structures and their relationship with the performance and survival of breeds and species. The aim of this study was to describe the ontogenetic characteristics of the weight of certain bone elements of the Sanmartinero creole bovine breed, from an early age (6 months) until maturity. A total of 79 females of the Sanmartinero creole bovine breed with an age range of 0.5 to 10 years were studied. Body measurements were obtained individually using standard procedures: cannon perimeter, thoracic perimeter, body length, withers height, and body weight. Functional and production indices were obtained for animals aged more than 3 years (n = 53): corporal index, anamorphosis index, dactylo thoracic index, and the relative thickness of the cannon. The correlation between body weight and the cannon perimeter showed no trend towards a plateau. In the Sanmartinero creole bovine, therefore, a very early development of the cannon perimeter is detected, which could lead to bone fragility in heavier animals. Therefore, data suggest little harmony with appendicular bone development, i.e., with less robust cannons which are those necessary to support body mass. It is suggested that in genetic improvement programs of the Sanmartinero creole bovine, the measurement of the cannon perimeter, the withers height, and the thoracic perimeter should be considered.

Environmental and Breed Risk Factors Associated with the Prevalence of Subclinical Mastitis in Dual-Purpose Livestock Systems in the Arauca Floodplain Savannah, Colombian Orinoquia.

The aim of this study was to assess the environmental and breed risk factors associated with the prevalence of subclinical mastitis (SCM) in cows in the dual-purpose livestock system of Arauca, Colombian Orinoquia. Milk samples were taken from 1924 mammary quarters, corresponding to 481 cows on 28 different farms, and the California Mastitis Test (CMT) was applied. Risk factors associated with SCM were determined using multiple logistic regression analysis. The response variable was the presence (1) or absence (0) of SCM. Breed was included as a genetic risk factor, and daily milk production, number of cows in production, lactation month, calving number, cow age, climatic period, and body condition were included as environmental risk factors. The analysis of the odds ratio (OR) of significant effects indicated that the factors significantly associated with the presence of SCM were the number of cows (OR = 2.29; p = 0.005), milk production (OR = 0.88; p = 0.045), and the Taurus-Indicus breeds (OR = 1.79; p = 0.009) and composite breed (OR = 3.95; p = 0.005). In this study, the occurrence of SCM was determined by the following risk factors: number of cows, milk production, and breed. Likewise, the highest prevalence seemed to occur on farms with less technological development and sanitary management of producers from the lowest socioeconomic stratum.

Chemical Composition and In Vitro Ruminal Fermentation Characteristics of Native Grasses from the Floodplain Lowlands Ecosystem in the Colombian Orinoquia.

Grasses from lowland ecosystems in flooded savannahs are useful to feed extensive grazing animals; however, scarce information about its agronomic and fermentation characteristics exists. This study aims to determine the chemical composition and fermentation parameters of native grasses from the floodplain lowlands ecosystem in the Colombian Orinoquia. Three native grasses (Leersia hexandra, Acroceras zizanioides and Hymenachne amplexicaulis) and a "control" grass (introduced Urochloa arrecta-Tanner grass) were sown and sampled at 30, 40 and 50 days of age. On each sampling date, biomass production in a 1 m2 frame was estimated, and the chemical composition and fermentation parameters were analyzed using near-infrared spectroscopy and the in vitro gas production technique, respectively. Data were analyzed using a mixed model for repeated measures and the least significant difference (LSD) was used for mean differentiation (p < 0.05). The grasses' nutritional characteristics varied as follows: dry matter (DM, 0.7-2.0 ton/ha), crude protein (CP, 6.1-12.2%), neutral detergent fiber (NDF, 56.6-69.6%), ash (5.8-15.8%) and dry matter digestibility (DMD) between 20.8 and 60.6% from 12 to 48 h of fermentation. Native plants such as L. hexandra and A. zizanioides presented higher biomass production, CP, ash, cellulose, and Ca levels than the control plant. During the experimental period (30 to 50 days), the grasses did not present significant nutrient availability changes. In terms of fermentation characteristics, L. hexandra increased ammonia concentrations and total volatile fatty acids (TVFA) and butyric acid. This latter effect was also observed in A. zizanioides grass. L. hexandra and A. zizanioides grasses constitute a valuable alternative forage resource during the flooding times of the studied ecosystem.

Basicranial Modular Organization. A Study in the Araucanian Horse of Colombia.

The skull is divided into neurocranium and splanchnocranium, and its variation allows ecomorphological studies to learn about possible evolutionary and adaptive characteristics. The basicranial organization of the neurocranium and splanchnocranium modules was studied in a sample of 31 skulls from adult Araucanian horses by means of 2D geometric morphometric techniques. The neurocranium and splanchnocranium modules on the ventral aspect were analyzed separately using a set of 31 landmarks. The RV coefficient (the multivariate analog of a correlation) was estimated to analyze the independence of these two parts, as well as their morphological integration, using a two-block analysis of least squares. The study results confirm the modular development of the neurocranium and the splanchnocranium, the former being more stable than the latter as well as low morphological integration between the two. The development between both parties is structured in a modular way but allows relative independence. Now it would be interesting for future studies to add muscles (those that connect the cranial parts, but also the cervical), the hyoid apparatus, and the ossicles of the internal ear and the jaw and analyze if they behave as integrated modules between them. Since this research has been conducted at the subspecific breed level, it could be plausible that in other breeds, this integrative development was different.

Examination of Shape Variation of the Skull in British Shorthair, Scottish Fold, and Van Cats.

A variety of skull shapes are frequently used for discrimination between animal species, breeds, and sexes. In this study, skulls of three different breeds of cats were examined by the geometric morphometric method, with the aim of revealing skull shape differences. For this purpose, 27 cats (6 British Shorthair, 7 Scottish Fold, and 14 Van cats) were used. The skulls of cats were modeled by computed tomography. Geometric morphometrics was applied using dorsal (8 landmarks, 63 semilandmarks) and lateral (8 landmarks, 63 semilandmarks) skull projections on these models. Centroid size differences between the breeds were statistically insignificant. However, the differences in shape were statistically significant for both the dorsal view and lateral view. Shape variation was less in the British Shorthair than in other breeds. Shape differences generally occurred around the orbit. In the skull of Scottish Folds, the orbit was situated more caudally than in other breeds. The British Shorthair had the largest orbital ring. In dorsal view, the Scottish Fold had the largest orbital diameter. The orbital ring of Van cats was smallest in both dorsal and lateral views. In the canonical variate analysis, it was seen that the breeds were separated from each other. The shape difference in the skull between different cat breeds could be revealed by geometric morphometrics. The results of this study provide useful information for taxonomy.

Morphological Differences between Sheep and Goat Calcanea Using Two-Dimensional Geometric Morphometrics.

The distinction between bones of sheep and bones of goats is a difficult issue in zooarchaeology. Several studies undertaken in the past to facilitate this task have relied upon both qualitative criteria and osteometry. Geometric morphometrics has proved to be a powerful tool to evaluate morphological differences in a rigorous and detailed manner. This study aims to analyse variations in the morphology of the calcaneum among sheep and goats based upon two-dimensional geometric morphometrics (GM). Twenty landmarks were selected on the surfaces of 79 calcanea (47 sheep and 32 goats) to calculate the principal components of shape variations among these specimens. Clear interspecific differences in the morphology of this bone were extracted. Most are located on the calcaneal tuber and neck, the sustentacular tali region, the articular surfaces of both the malleolus and the cubonavicular. Furthermore, the use of GM methods has enabled us to assess small but significant amounts of geometric variation that are difficult to measure using traditional morphometric techniques. They provide a new and useful perspective to what is already known in the published literature. Our results shed new light upon the possibility of the existence of qualitative features that may help to distinguish caprine breeds.

Would the Cephalic Development in the Purebred Arabian Horse and Its Crosses Indicate a Paedomorphic Process?

This study examined paedomorphosis in PAH and F1 crossbreds. A sample of 99 horses was selected from 40 different breeders and consisted of three groups: stallions (n = 16), mares (n = 53), and geldings (n = 30), ranging from 10 months to 27 years in age. All horses presented a concave celloid lateral left head profile in the acquired photographic images. The hypothesis proposed in this study suggested the lateral profile of the head in juveniles was representational in the adult form due to the neonate's facial bones (part of the splanchnocranium) developing at a different rate to those of the skull. The methodology utilized geometric morphometrics to identify 23 landmarks so as to identify profile curvature indicative between the three groups (stallions, mares, and geldings). Principal component analysis reduced the number of variables to 14 examinable landmarks. Using a two-NPMANOVA and multivariate regression test, it was demonstrated that an isometric relationship between the concave celloid profile in the juvenile and its adult counterpart existed. This result supported the hypothesis that PAH and F1 crossbreds expressed a paedomorphic trait due to the adult form retaining the concave celloid profile identified in the juvenile.

No Morphological Integration of Dorsal Profiles in the Araucanian Horse (Colombia).

The aim of this research was to determine if the division between the cervical, dorsal, and croup profiles (three regions commonly assessed for descriptive profile purposes) has a modular basis as well as a morphological integration. For this, a total of 135 digital photographs were obtained, in a lateral view, of adult horses (14 females and 121 geldings; age range: 2-20 years), of the Araucanian breed, an equine population typical of the flooded savannah of Arauca, NE Colombia. From each image, 25 reference points (semi-landmarks) were obtained at the dorsal level of the neck, back, and croup. The hypothesis of the modularity of different body profiles based on differentiated regions was tested using the RV coefficient, and an analysis of two blocks of partial least-squares allowed the evaluation of the level of morphological integration. The results showed that each alloidic group reflected high integration but low modularity. The covariation between the modules was centered mainly on the withers, the loin, and the croup. For the studied profile blocks, no module can be considered. The absence of the fragmentation of the alloidic sets would promote the adaptive capacity of the breed by linking coordinated functional responses to similar selection pressures, e.g., field work. Although the integration between the neck, back, and croup profiles was proven, their modular covariation was low.

Shape Directional Asymmetry in Hindlimb Pairs among Calves (Bos Taurus).

The aim of this study was to determine paired asymmetries (right-left) in the autopods of bovine hindlimbs using geometric morphometry (GM). A total of 28 hindlimb right-left matched autopods belonging to healthy Brown Pyrenean calves were assessed. Dorsoplantar radiographs were obtained for each autopod. The bone shape was compared on right and left pairs by means of GM techniques, using a set of 15 landmarks. The results suggest that right and left distal limbs are, despite a perceived resemblance of symmetry, differently directionally developed in shape, with right hindlimbs tending to supinate (rotate outwards) and left hindlimbs tending to pronate (rotate inwards). This unevenness is probably related to the mediolateral forces' contribution of each limb in carrying out the tasks of propulsion and control during walking, and/or a consequence of a laterality associated with a lateralized grazing posture. Our findings prompt a new reassessment of the function of each bovine hindlimb during standing and locomotion.

Symmetry-Breaking Stabilities in Carapace Curvature on Testudo (Reptilia, Testudinidae).

The aim of this research was to contribute to the study of the doming geometry of Testudo carapace as an unstable point of equilibrium when animals are overturned. We performed this research using geometric morphometric using a sample of 64 Testudo individuals belonging to different species (T. hermannin = 30, T. graecan = 3, T. marginata n = 13 and T. horsfieldii n = 18), sexes and ages. A set of four sagittal landmarks (discrete homologous points) and 15 pairs of semi-landmarks, on the frontal doming of the carapace, were digitized on individual carapace pictures. Significative fluctuating asymmetry was detected, defined as small, completely random departures from bilateral symmetry, but much less than directional asymmetry, which appeared highly significative. Anti-symmetry did not appear. Carapace asymmetry was dominated by a clear right directionality. A possible biological speculation could be that this asymmetry more that easing the self-righting potential ("kinematic instability", understood as the ability to self-right without effort), makes stable ventral turning difficult ("static stability", understood as the ability to resist passively turning the body produced by destabilizing forces). This asymmetry is present among both sexes but more marked among males. An explanation for this sexually differentiated pattern could be the higher locomotion and the fight for mating in males, making them consequently more prone to losing their balance and falling on their back. These data may be useful in studying adaptative traits in Testudo species as well as establishing a seminal base for future studies. This research is the first attempt to explore a suitable method to assess doming asymmetry which could be useful in future, more extensive investigations, on a larger interspecific sample.

No modularity at ventral level in the horse skull.

Morphological integration and modularity are concepts that refer to the covariation level between the components of a structure. Morphological modules are independent subsets of highly correlated traits. The horse skull has been studied as a whole functional structure for decades, but the integrative approach towards quantitative examination of modules is scarce. We report here the first evaluation of cranial modularity in the horse at basal level. For this, we studied the modularity hypothesis for splanchnocranium and basicranium modules in the horse, two phenotipic regions under local influence by soft-tissue-hard-tissue interfaces. Using geometric morphometrics to capture the shape and location, we examined both modules in a sample of 23 dry skulls belonging to Pyrenean Horse Breed using 57 two-dimensional cranial landmarks. Modules were compared through partial least squares analyses and Escoufier (RV) coefficient. We tested whether the integration (measured by Escoufier RV coefficient) of splanchnocranium and basicranium strength modules and their covariation pattern (as analysed by partial least squares analysis) subordinate and express similar integration results. A clear modularity was observed. The lack of disproportions in the skulls of domestic horse breeds (compared to dog and cat breeds, for instance) might be an expression of the lack of single modules to evolve. On the other side, integration might have a positive impact on survival as long as the selection pressure is along the trajectory of integrated variation.

Comparación del neurocráneo entre el gato doméstico (Felis catus Linneas 1758) y el montés (Felis silvestris Schreber, 1777) mediante técnicas de morfometría geométrica / Comparison of neurocranium between domestic cat (fFlis catus Linneas 1758) and wild cat (Felis silvestris Schreber, 1777) by means of geometric morphometric techniques

RESUMEN: El objetivo de este estudio fue comparar objetivamente las diferencias en la forma total (tamaño y forma pura) del neurocráneo entre un grupo de cráneos de gatos domésticos (Felis catus, n=81), y un grupo de gato montés (Felis silvestris, n=12) mediante técnicas de morfometría geométrica. Para ello se obtuvieron fotografías digitales del lado izquierdo de los cráneos de un modo estandarizado, y en las que se ubicaron 8 landmarks y 9 semilandmarks. Después de una superposición generalizada de Procrustes se procedió a un análisis de componentes principales y a otro de canónico a fin de comparar y detectar las posibles diferencias. Los tamaños neurocraneales no mostraron diferencias entre ambos grupos, pero sí que aparecieron diferencias significativas en la forma. Los cambios de forma afectarían principalmente la sutura escamoso-parietal-alisfenoidal y, en menor medida, puntos caudales del cráneo, lo que sugeriría cambios a nivel de músculos masticatorios. A conocimiento del autor, constituye esta la primera investigación que caracteriza y compara el cráneo de los gatos mediante métodos de morfometría geométrica, recomendándose un mayor uso de esta técnica dada la escasez de publicaciones al respecto en mamíferos domésticos.

SUMMARY: The objective of this study was to objectively compare the differences in the total shape (size and pure shape) of the neurocranium between a group of domestic cat skulls (Felis catus, n=81), and wildcats (Felis silvestris, n=12) by means of geometric morphometric techniques. To achieve it, we obtained digital photographs of the left side of the skulls in a standardized form, in which 8 landmarks and 9 semilandmarks were located. After a Generalized Procrustes Superimposition, a Principal Component Analysis and a Canonical Analysis one were performed to compare and detect possible differences. Neurocranial sizes showed no differences between the two groups, however, significant differences in shape did appear. Shape changes would mainly affect the squamosal-coronal suture and, to a lesser extent, caudal skull points, therefore suggesting changes in masticatory muscles. As far as this author´s knowledge, this is the first research that characterizes and compares the skull of cats using geometric morphology methods, recommending greater use of this technique given the scarcity of publications on this subject in domestic mammals.

Diferencias morfométricas en el hueso palatino de la oveja (Ovis aries) y la cabra (Capra hircus) / Morphometric palatine differences between sheep (Ovis aries) and goat (Capra hircus)

RESUMEN: Un hueso craneal muy poco estudiado en anatomía veterinaria comparada es el palatino. En nuestro estudio, realizamos la comparación de este hueso entre la oveja (Ovis aries L., 1758) y la cabra (Capra hircus L., 1758), a partir de una muestra de 36 y 17 cráneos respectivamente, y utilizando métodos de morfometría geométrica. Se eligieron un total de 32 puntos (4 hitos y 28 semi-hitos) para analizar la lámina horizontal del hueso palatino. Se reflejaron diferencias estadísticamente significativas tanto para el tamaño como para la forma. En Capra se denota una clara expansión lateral del hueso y rostral y una contracción central, con un acercamiento relativo de los forámenes palatinos, mientras que en Ovis los forámenes están más lateralmente alejados. A nuestro parecer, esta mayor anchura y longitud de la lámina horizontal en Capra se explicaría por una mayor capacidad de frotación del alimento en relación a Ovis.

SUMMARY: Palatine is a cranial bone very less studied in comparative veterinary anatomy. In our study, we performed the comparison of this bone between sheep (Ovis aries L., 1758) and goat (Capra hircus L., 1758), from a sample of 36 and 17 skulls respectively, using methods of geometric morphology. A total of 32 points (4 landmarks and 28 semi-landmarks) were chosen to analyse the horizontal lamina of the palatine bone. Statistically significant differences were reflected for both size and shape. Capra denotes a clear lateral expansion of the bone and rostral and a central contraction, with a relative approach of palatine foramina, while in Ovis foramina are more laterally distant. In our view, this greater width of the horizontal lamina in Capra would be explained by a greater capacity to rub the food compared to Ovis.

A comparative analysis of sphenoid bone between domestic sheep (ovis aries) and goat (capra hircus) using geometric morphometrics.

The sphenoid bone forms the rostral part of the base of the neurocranium and is composed of two segments, the presphenoid [os praesphenoidale] and the basisphenoid [os basisphenoidale]. Rarely studied in osteology, we tested whether it can provide distinctive features between domestic sheep (Ovis aries L., 1758) and goat (Capra hircus L., 1758). For this goal, we studied a sample comprised by 53 dry modern skulls of adult sheep (n = 36) and goat (n = 17) subjects from a modern comparative collection by means of geometric morphometric techniques using a total of 26 anatomical points (2 saggital landmarks and 24 semilandmarks). Results showed that form (size + shape) differences appear between both species: sphenoid among sheep tends to be bigger, longer and wider than in goats, differences of width being mainly located on basisphenoid width.

Sexual Allometric Monomorphism in Araucan Pig from Colombia: Preliminary Results.

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.

Asymmetries of Forelimb Digits of Young Cattle.

Based on the anatomical premise that, in bovines, the medial (inner) hoof is larger than the lateral (outer) one in the forelimb, we hypothesized that this implies a phalangeal form difference. To test this hypothesis, asymmetries of the forelimb acropodia (phalangeal series) were studied on calves belonging to the Brown Pyrenean breed, a meat breed managed under extensive conditions in NE Spain. Dorso-palmar radiographs were obtained for each acropodium in a sample of 17 paired left and right forelimbs. Size and shape were analysed by means of geometric morphometrics on medial and lateral acropodial series (III and IV series respectively) for each left and right limb. Shape coordinates were computed by Generalized Procrustes Analysis. Medial and lateral acropodial series appeared similar in size, but their shape expressed an especially high directional asymmetry, with distal phalanges (pedal bones) being abaxially (outwards) oriented. Such morphological observations may be an important reconsideration of "normal" radiographic acropodial symmetry evaluation. This can be explained not only by an unevenly distributed ground reaction force between acropodial series, but also between right and left limbs, making medial and lateral hoof surfaces differently prone to overloading and, accordingly, to injuries to the limb.

Lineal Discrimination of Horses and Mules. A Sympatric Case from Arauca, Colombia.

This is the first morphological comparative study between local horses and mules from Arauca, Colombia. It was realized to compare morphological traits between both species by analysing 15 adult mules (7 males and 8 females) and 150 adult horses (137 males and 13 females), with an age interval from 2 to 22 years. Data consisted of 24 different body quantitative traits which can explain the body conformation: thoracic circumference, body length (BL), thoracic depth and width, withers height (WH), sternum height, shoulders width, chest width, forelimb cannon perimeter and length, head length and width, skull length and width, face length and width, ear length and width, loin height, croup height (CrH), width and length, dock height (DoH), and hock height. Heart girth circumference, body length, withers height, croup height, and dock height were the most discriminative traits, showing statistical differences between species. The formula is X = (BL × 0.402) + (WH × 0.323) + (CrH × 0.352) + (DoH × 0.384). A value of X > 184.5 assigns with total certainty that a skeleton belongs to a horse, and if X < 174.0, it is a mule. The proposed formula has a 100% specificity but a 71.4% sensibility for mules and an 84.4% for horses into the rank of 174.0-184.5. Therefore, results demonstrate that some postcranial anatomical elements of Equus could give enough information for a bone differentiation between horses and mules, at least in animals from the Araucan region, but the main interest is that it reflects the possibility to differentiate morphometrically both species from bone remains when horses and mules were sympatric.

Los tipos craneométricos caninos aparecen bien expresados a nivel de conformación del arco cigomático / Craneometric canine types are well expressed at the level of the zygomatic arch conformation

Dentro del espectro de conformación del cráneo, se reconocen generalmente tres amplias categorías que se corresponden con el concepto de biotipo cefálico, determinado por el Índice Cefálico. El Estos tres biotipos cefálicos son: el braquiocefálico, mesaticefálico y dolicocefálico, pero están basados en medidas lineales. A fin de revisar esta clasificación en base a su geometría, se estudiaron 53 cráneos de perros adultos, correspondientes a los tres grupos craneométricos descritos: 16 braquicéfalos, 20 mesaticéfalos y 17 dolicocéfalos. Para ello se obtuvieron fotografías en el plano ventral, en las que posteriormente se ubicaron 17 hitos anatómicos que se analizaron mediante técnicas de morfometría geométrica. De estos hitos, 5 correspondían a la zona neurocraneal y el resto al esplacnocráneo. Los tres grupos craneométricos mostraron diferencias estadísticamente significativas entre ellos tanto por el tamaño como por la forma. Las variables que contribuyeron más a explicar la diferenciación fueron las ubicadas en el margen más lateral de los arcos cigomáticos y en la base de este mismo arco. Las variables esplacnocraneales presentaban una alometría mucho más marcada que las neurocráneos. Puesto que el arco cigomático debe ser considerado como parte del esplacnocráneo, sugerimos que es tan importante el índice cefálico (que tiene en cuenta la máxima anchura de la cabeza) como el facial (que tiene en cuenta la máxima anchura de la cara). La conformación neurocraneal sería mucho más conservativa y por ende el índice craneal, de mucho menor poder discriminatorio entre grupos. El cambio entre tipos se debería a los músculos masetero y temporal, que tienen su inserción en el arco.

Within the wide conformation of skull spectrum, there are generally three recognized broad categories that correspond to the concept of cephalic biotype, determined by the cephalic index. The three cephalic biotypes are: brachiocephalic, mesaticephalic and dolichocephalic, which are based on linear measures. In order to revise this classification based on its geometry, we studied 53 skulls of adult dogs, corresponding to the three craneometric groups previously described: 16 brachycephalic, 20 mesaticephalic and 17 dolichocephalic. Images on ventral plane were obtained and 17 anatomical landmarks were subsequently located and analyzed by means of geometric morphometric techniques. Five of those landmarks corresponded to the neurocraneal area and the rest of the splanchnocranium. The three craneometric groups showed statistically significant differences between them for both size and shape. The variables that contributed to the differentiation between them were located along the edge of the zygomatic arches and on the basis of this arch. Splanchnocranial variables also presented a much more marked allometry than the neurocraneal variables. Since the zygomatic arch should be considered as part of the splanchnocranium, we suggest that the cephalic index (which takes into account the maximum width of the head) is as important as the facial index (which takes into account the maximum width of the face). The neurocraneal index would be much more conservative, and therefore less discriminatory between the groups.