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Introduction
Criollo cattle breeds descend from the cattle (Bos taurus) that arrived in the Americas with the Spaniards from the Iberian Peninsula between 1493 and 1521 (De Alba, 2011). Throughout 500 years, these animals colonized the different agroecological regions of the Americas (Villalobos-Cortés et al., 2009), adapting to diverse ecosystems as a result of natural selection, and developing resistance to diseases and to variations in the amount and quality of forages (Landi & Quiroz, 2011). However, even though in the past this genetic resource was the basis of livestock activity, present these cattle are considered in risk of extinction because the cattle producers that preserve and use these breeds are only a few, most of them indigenous located in mountainous and wooded areas that are hard to access, thus limiting their training to improve the productive management of the animals and their selection for a specific zootechnical purpose (Perezgrovas-Garza & de la Torre-Sánchez, 2015).
In some regions of the states of Oaxaca, Guerrero, and Puebla there are still isolated nuclei of criollo cattle, mainly in mountainous and semidesertic areas, where one cattle breed known as Mixteco criollo has developed and is raised mostly by indigenous people under rustic systems of extensive silvopastoral production (Méndez et al., 2002). These cattle are commonly used to obtain weaned calves for fattening and meat production. Nonetheless, the productive system used by these cattle producers, which is extensive with no territorial restriction, has led to a decrease in the population of this animal genetic resource because it exposes the few criollo cattle individuals to indiscriminate and uncontrolled crosses with cattle of other Bos taurus and Bos indicus breeds, such as Brahman, Nelore, Angus, Beefmaster, Simmental and Simbrah, which roam loose in the same territory because they are owned by neighboring producers that also manage them extensively (Severino-Lendechy et al., 2021). This situation leads to the loss of genetic material and reduces the population of purebred Mixteco criollo cattle.
The conservation of animal genetic resources requires their characterization (Landi & Quiroz, 2011). The morphometric characterization establishes racial patterns from different body measurements, analyzes the relationships among individuals, and evaluates the harmony of the morphostructural model (Martínez-López et al., 2014; Parés i Casanova, 2009). Therefore, morphometric characterization is basic for the technical and scientific knowledge of new animal breeds and constitutes the first step toward conservation and protection (Contreras et al., 2012).
On the other hand, the body measurements used for the morphometric characterization are utilized to generate some zoometric indices, which are employed to determine a specific biotype or zootechnical purpose of the animal (meat, milk, or dual-purpose) that allows obtaining some productive profits (Contreras et al., 2011; Landi & Quiroz, 2011).
In the literature, there is only one study on the Mixteco criollo cattle that describes morphometric variables, but not their zoometric indices or their zootechnical purpose (Méndez et al., 2002). Therefore, the objective of this study was to determine the morphometric variables and the zoometric indices of Oaxaca Mixteco criollo bulls to know the degree of morphostructural harmony among the individuals, their ethnological characters, and their specific biotype.
Material and Methods
The Commission of Bioethics and Animal Welfare of the Facultad de Medicina Veterinaria y Zootecnia of the Universidad Veracruzana approved the experimental procedures that were used on the animals from this study, which comply with what is established in the NOM-062-ZOO-1999.
Geographical location of the study site
The study was conducted in 10 cattle production units (UP) located in the municipality of Huajuapan de León (Lat. 17°48’14’’ North and Long. 97°46’33’’ West), in the state of Oaxaca, Mexico, at altitude 1641 masl, with semi-warm humid climate with summer rainfall, mean annual temperature of 20 °C, and annual rainfall of 736 mm (INEGI, 2022).
Characteristics of the animals
Thirty bulls that fitted the racial pattern of the Mexican criollo cattle (Espinoza-Villavicencio et al., 2009; Méndez et al., 2002) were selected from 10 UP of the municipality of Huajuapan de León, Oaxaca, through a convenience sampling. The average age and weight of the bulls were 2.3 ± 0.8 years and 248.8 ± 27 kg. The bulls were visually examined to confirm that they were free from pathologies or physical defects that could alter the morphometric measurements. They were kept under the usual management of the UP regarding sanitary measures and feeding, the latter being continuous extensive grazing.
Morphometric characterization
Ten morphometric variables were measured (in centimeters) in each bull using the morphometric standard for the Mixteco criollo cattle proposed by Méndez et al. (2002). The variables measured were: head width (ACa), head length (LCa), corporal length (LCo), height at the withers (ACr), thoracic perimeter (PTx), dorsal-sternal height (ADE), thoracic bicostal width (ABTx), rump length (LGr), rump width (AGr), and the metacarpus perimeter (PC) (Aguirre-Riofrio et al., 2019; Méndez et al., 2002). To obtain the measurements of length, width, height, and perimeter, a measuring tape and zoometric sticks were used. To facilitate obtaining the measurements, the bulls were immobilized in a chute. The live weight of the animals was determined using a portable scale with a maximum capacity of 500 kg (FSK-Basic, A and A Scales, EUA), and their age was calculated through dental chronology (Casas et al., 2001).
Zoometric indices
The zoometric indices indicate relationships among quantitative morphological variables, and they have been established as patterns to define the different types or breeds in which animals and their zootechnical purposes (milk, meat, or dual-purpose) can be classified (Contreras et al., 2011; Parés i Casanova, 2007, 2009; Salamanca & Crosby, 2013a). The zoometric indices are calculated from the morphometric variables. The most commonly used are (Aguirre-Riofrio et al., 2019; Contreras et al., 2011; 2012; Fernández et al., 2007; Casanova, 2007; 2009; Rodríguez et al., 2001; Salamanca & Crosby, 2013a,b):
1) Cephalic index (ICEF): it measures the proportionality of the head of the animal. It classifies the animals as dolichocephalic (index ˂75.9; long and slim head), brachycephalic (index ˃81; short and wide head), and mesocephalic (index between 76 and 81; facial proportion apparently symmetrical, namely, the facial proportion of the head is apparently the same as its width).
2) Thoracic index (IT): it reflects the variations in the shape of the thorax; higher values (more circular) correspond to beef cattle and lower values (more elliptical) to dairy cattle. The mediolinear breeds have an IT between 86 and 88, the brevilinear breeds ≥89, and the longilinear breeds ≤85.
3) Corporal index (ICO): it classifies the animals as brevilinear (≤85), mesolinear (86-88), or longilinear (≥90).
4) Lateral corporal index (ICL): it indicates whether an animal is tall rather than long, or vice versa; a lower value indicates that the shape of the animals is close to a rectangle, which is the predominant shape of beef cattle.
5) Anamorphosis index (IA): it relates the thoracic perimeter with the height at the withers, and provides indications of the aptitude for meat production of the animal; as the index decreases it indicates that the animal has long legs and is lighter, suggesting a tendency to the production of lean meat, whereas as the index increases it indicates that the animal has the tendency to produce fat. It is, if in cattle this value is high (4.0 and 5.0) it corresponds to an animal with a tendency to produce meat, and if the index is low (2.5 and 3.0) it corresponds to an animal with a tendency to produce more milk than meat.
6) Pelvic index (IP): it indicates the relationship between the width and length of the pelvis, reflecting a pelvis that is proportionally wider than long, or vice versa. A higher value indicates a pelvis which is wider than long, which is observed in an animal with a tendency to produce meat rather than milk.
7) Dactyl-thoracic index (IDT) and 8) Dactyl-costal index (IDC): they give an idea of the degree of refinement of the skeleton, being their value higher in animals with a tendency to produce meat rather than milk.
9) Transverse pelvic index (IPT): it relates the development of the rump with the body size; as it exceeds 33, the animal is considered with a tendency to meat production.
10) Longitudinal pelvic index (IPL): it relates the length of the rump with the height at the withers, indicating that as the value increases, the animal is larger; a value above 37 indicates an animal for meat production.
In this study, based on the morphometric variables 10 zoometric indices were determined, which provided information on the ethnological characteristics and the productive aptitude (milk and meat) of the animals. To achieve this, the formulas described by Parés i Casanova (2009) and Aguirre-Riofrio et al. (2019) were used (Table 1).
Table 1 Formulas used to calculate the zoometric indices of cattle and type of information they provide.
| Information | Index | Formula |
|---|---|---|
| Ethnological characters | Cephalic (ICE) | ICE = (head width/head length) x 100 |
| Thoracic (ITO) | ITO = (bicostal width/dorsal-sternal height) x 100 | |
| Corporal (ICO) | ICO = (body length/thoracic perimeter) x 100 | |
| Lateral corporal (ICL) | ICL = (height at the withers/body length) x 100 | |
| Anamorphosis (IAN) | IAN = thoracic perimeter2/(height at the withers x 100) | |
| Pelvic (IPE) | IPE = (rump width/rump length) x 100 | |
| Milk producing aptitude | Dactyl-thoracic (IDT) | IDT = (metacarpus perimeter/thoracic perimeter) x 100 |
| Dactyl-costal (IDC) | IDC = (metacarpus perimeter/thoracic bicostal width) x 100 | |
| Meat producing aptitude | Transversal pelvic (IPT) | IPT = (rump width/height at the withers) x 100 |
| Longitudinal pelvic (IPL) | IPL = (rump length/height at the withers) x 100 |
Sources: Parés i Casanova (2009) and Aguirre-Riofrio et al. (2019).
Statistical analysis
The morphometric variables and zoometric indices were analyzed using descriptive statistics including mean, standard deviation (SD), minimum value (Min), maximum value (Max), and coefficient of variation (CV). The morphometric measurements were correlated using simple linear correlation (r) to determine the degree of association between variables. All the analyses were conducted using the software Statistical Package for Social Sciences version 19 (SPSS V.19).
Results and Discussion
Morphometric measurements
The morphometric measurements obtained in the Oaxaca Mixteco criollo bulls (Table 2) provided a general approximation of the physical characteristics of the animals, showing a range of variation between 7.4 % (ACr) and 29.3 % (ABTx) (Table 2), with an average CV of 13 %. This differs from the information reported in limonero criollo in Venezuela, in which the measurements that were evaluated showed low variability, being 3.3 % for height at the withers and 10.8 % for hip perimeter, with average CV of 6.6 % (Contreras et al., 2012). In Argentinian criollo cattle, the range of variability was 3.7 % for height at the rump and 13.4 % for head width, with an average CV of 7.7 % (Martínez et al., 2007). These differences in the range of variability and CV can be attributed to the low genetic selection of the Oaxaca Mixteco criollo bulls. Nonetheless, according to the weight and size, it was determined that this breed is eumetric (medium weight and small to medium size), and according to its regional morphology (head, torso, rump, and extremities) this breed has mediolinear proportions.
Table 2 Morphometric variables in Mixteco criollo bulls.
| Variable (cm) | Mean ± SD | Min | Max | CV (%) |
|---|---|---|---|---|
| Head width (ACa) | 21.9 ± 5.1 | 17 | 45 | 23.3 |
| Head length (LCa) | 45.2 ± 3.4 | 17 | 45 | 7.6 |
| Corporal length (LCo) | 123.6 ± 15.1 | 95 | 153 | 12.2 |
| Height at the withers (ACr) | 115.7 ± 8.6 | 101 | 130 | 7.4 |
| Thoracic perimeter (PTx) | 154.8 ± 14.8 | 130 | 183 | 9.6 |
| Dorsal-sternal height (ADE) | 56.1 ± 8.4 | 39 | 70 | 14.9 |
| Thoracic bicostal width (ABTx) | 38.9 ± 11.4 | 24 | 59 | 29.3 |
| Rump length (LGr) | 43.8 ± 3.4 | 38 | 51 | 7.8 |
| Rump width (AGr) | 37.2 ± 5.9 | 30 | 56 | 15.8 |
| Metacarpus perimeter (PC) | 17.1 ± 1.5 | 15 | 21 | 9.1 |
SD = standard deviation. CV = coefficient of variation.
The morphometric measurements ACa and LCa in the Oaxaca mixteco criollo were similar to those reported in lojano criollo (ACa 21 ± 0.3, LCa 46 ± 0.6; Aguirre-Riofrio et al., 2019), but different to those obtained in limonero criollo (ACa 26.7, LCa 49.08; Contreras et al., 2012) and blanco orejinegro (ACa 49.0 ± 1.3, LCa 50 ± 2.4; Rojas-Jiménez et al., 2014). This body region is important because it allows to establish differences in the comparative studies by sex within and between breeds (Contreras et al., 2012). In addition, the ethnological characteristics contributed by the head are very useful because they are not influenced by environmental and managemental factors, allowing to establishment particular characteristics for each breed (Parés i Casanova, 2009).
The Oaxaca mixteco criollo bulls showed short LCo, smaller than other criollo breeds such as the limonero in Venezuela (LCo 132.04; Contreras et al., 2012), chinampo in Mexico (LCo 128; Espinoza-Villavicencio et al., 2009), and lojano in Ecuador (LCo 179; Aguirre-Riofrio et al., 2019). Additionally, due to its ACr the Oaxaca mixteco criollo is considered a small size breed, similar to the Suriname (ACr 112.70; Tjon A San & Molina-Flores, 2016) and the lojano (ACr 111; Aguirre-Riofrio et al., 2019), but smaller than other criollo breeds such as the blanco orejinegro (ACr 122; Rojas-Jiménez et al., 2014), limonero (ACr 126.65; Contreras et al., 2012), and the Manabi in Ecuador (ACr 131.90; Cevallos-Falquez et al., 2016).
The PTx of the Oaxaca mixteco criollo was similar to those reported in lojano (PTx 151; Aguirre-Riofrio et al., 2019) and Casanare (PTx 156; Salamanca & Crosby, 2013b) criollos, but wider than the PTx of the criollos chinampo (PTx 137; Espinoza-Villavicencio et al., 2009) and Suriname (PTx 142; Tjon A San & Molina-Flores, 2016). The ADE and ABTx were similar to those obtained in lojano criollo (ADE 59, ABTx 35; Aguirre-Riofrio et al., 2019), and smaller than those of the Puno (ADE 67, ABTx 53; Rojas-Espinoza & Gómez-Urviola, 2005) and the Santa Elena (ADE 62.5 y ABTx 42.2; Cabezas-Congo et al., 2019) criollos. The LGr and AGr were similar to those recorded in the lojano (LGr 43, AGr 39; Aguirre-Riofrio et al., 2019), Santa Elena (LGr 43, AGr 39.1; Cabezas-Congo et al., 2019), and Puno (LGr 47, AGr 39.1; Rojas-Espinoza & Gómez-Urviola, 2005) criollos. The PC was similar to the one reported in lojano criollo (16 ± 0.3; Aguirre-Riofrio et al., 2019) and narrower than in the Santa Elena criollo (19.29 ± 3.70; Cabezas-Congo et al., 2019).
The differences found between morphometric variables can be attributed to environmental and managemental factors that can influence the size, growth, and physical conformation of the animal (Contreras et al., 2011; Espinoza-Villavicencio et al., 2009), which is related to the zootechnical purpose of each breed (milk, meat, or dual-purpose) (Contreras et al., 2011; Espinoza-Villavicencio et al., 2009; González-Stagnaro & De la Fuente-Martínez, 2012; González-Stagnaro et al., 2006). However, the morphometry of the Mixteco criollo bulls indicated that these animals are well adapted to their environment, where adverse climatic, orographic, and feeding conditions exist.
Harmony of the morphometric model
The morphometric variables obtained in this study provided an approximation of the phenotypic characteristics of the Oaxaca Mixteco criollo cattle. However, to generate a harmonious morphometric model of the breed it was necessary to subject such variables to simple linear correlation analysis to determine the degree of association between the morphometric measurements. When in a group of animals or breeds more than 50 % of the variables are correlated, it corresponds to a harmonious morphometric model; when 25 to 50 % of the variables are correlated, it is defined as a moderately harmonious model; when less than 25 % of the variables are correlated, it corresponds to a little harmonious model (Contreras et al., 2011; Rojas-Jiménez et al., 2014).
To analyze the morphometric variables obtained in this study the methodology proposed by Herrera et al. (1996) and Rojas-Jiménez et al. (2014) was used, conducting a simple correlation analysis between the studied variables (Table 3). In 66.6 % of the cases, a correlation was observed between the different morphometric variables (p < 0.05); this result was superior to that obtained in Santa Elena criollo (55.2 %; Cabezas-Congo et al., 2019), similar to the one in limonero criollo in Venezuela (61.5 %; Contreras et al., 2011), but inferior to the results in other criollo breeds such as the pampa chaqueño (75.7 %; Martínez-López et al., 2014) and blanco orejinegro (88.2 %; Rojas-Jiménez et al., 2014). The percentage of correlations within each population, as well as the differences or similarities of correlation between the variables analyzed, are indicators of the underlying variability among populations, which could be expected in this type of populations that historically have been genetically managed by producers that use different criteria, which can or cannot include adequate genetic improvement and/or reproductive programs, as well as criteria for the selection of breed traits, besides the use of bulls of other breeds (Cabezas-Congo et al., 2019; Severino-Lendechy et al., 2021). Nonetheless, independently of the differences or similarities, the Oaxaca Mixteco criollo bulls showed harmony and proportionality in their morphostructural model.
In this study there was a positive correlation (p < 0.05) between live weight and 90.9 % of the morphological characteristics (Table 3), being PTx the variable with the highest correlation (r = 0.778) with weight. However, the values obtained were lower than those reported in limonero criollo (r = 0.93; Contreras et al., 2012), Lucerna (r = 0.94; Mahecha et al., 2002), and crossbred cattle (r = 0.94; Khalil & Vaccaro, 2002). According to Mahecha et al. (2002), although most of the variations in body weight modify the morphometric profile of the animal, which is reflected in the change in PTx, the live weight can be estimated almost exactly from this morphometric measurement, which itself is an indicator of growth, adaptability, and feed efficiency in cattle.
The results of the present study indicate that the percentages of correlation between these morphological variables can be modified by the genetic management of the herds leading to conserve or loss the characteristics of a specific breed and that the body measurement of PTx could be used to estimate the live weight of the animals.
Table 3 Phenotypic correlations (r) between weight and the morphometric variables of Oaxaca Mixteco criollo bulls, with p-values.
| LCa | ACa | LCo | ACr | ABTx | PTx | ADE | LGr | AGr | PC | |
|---|---|---|---|---|---|---|---|---|---|---|
| Peso | 0.456(*) | 0.299* | 0.403(*) | 0.418(*) | .0580(**) | 0.778** | 0.083 | 0.459** | 0.470** | 0.491** |
| p | 0.022 | 0.030 | 0.046 | 0.038 | 0.002 | 0.000 | 0.694 | 0.001 | 0.001 | 0.000 |
| LCa | 1 | 0.207 | 0.311 | 0.239 | 0.210 | 0.332 | 0.337 | -0.004 | 0.306 | 0.286 |
| p | 0.321 | 0.131 | 0.249 | 0.314 | 0.104 | 0.099 | 0.984 | 0.137 | 0.166 | |
| ACa | 1 | 0.225 | 0.371 | 0.059 | 0.357 | 0.333 | 0.224 | 0.081 | 0.161 | |
| p | 0.279 | 0.068 | 0.778 | 0.080 | 0.103 | 0.282 | 0.699 | 0.441 | ||
| LCo | 1 | 0.604(**) | 0.429(*) | 0.618(**) | 0.441(*) | 0.552(**) | 0.711(**) | 0.586(**) | ||
| p | 0.001 | 0.033 | 0.001 | 0.027 | 0.004 | 0.000 | 0.002 | |||
| ACr | 1 | 0.750(**) | 0.845(**) | 0.633(**) | 0.633(**) | 0.570(**) | 0.692(**) | |||
| P | 0.000 | 0.000 | 0.001 | 0.001 | 0.003 | 0.000 | ||||
| ABTx | 1 | 0.426(*) | -0.480(*) | 0.610(**) | 0.557(**) | 0.433(*) | ||||
| p | 0.034 | 0.015 | 0.001 | 0.004 | 0.031 | |||||
| PTx | 1 | 0.525(**) | 0.628(**) | 0.687(**) | 0.720(**) | |||||
| p | 0.007 | 0.001 | 0.000 | 0.000 | ||||||
| ADE | 1 | 0.169 | 0.425(*) | 0.641(**) | ||||||
| p | 0.421 | 0.034 | 0.001 | |||||||
| LGr | 1 | 0.638(**) | 0.748(**) | |||||||
| p | 0.001 | 0.000 | ||||||||
| AGr | 1 | 0.653(**) | ||||||||
| p | 0.000 | |||||||||
| PC | 1 |
p < 0.05* and p < 0.01** Statistical difference. Variables: Head length (LCa), Head width (ACa), Corporal length (LCo), Height at the withers (ACr), Thoracic bicostal width (ABTx), Thoracic perimeter (PTx), Dorsal-sternal height (ADE), Rump length (LGr), Rump width (AGr), and Metacarpus perimeter (PC).
Zoometric indices
The studied indices in general showed a range of variation between 4.4 % (IDT) and 41.2 % (IT) (Table 4), being the thoracic index the less homogeneous. Nonetheless, the average CV was 12.8 %. Therefore, these data allowed to define the Oaxaca Mixteco criollo bulls as a dolichocephalic biotype (ICEF 48.5 ± 4.2) with brevilinear body (ICO 79.9 ± 7.8), with aptitude for the dual-purpose but with tendency to produce meat (ICL 94.4 ± 9.0, IDT 11.0 ±0.5, IDC 46.6 ± 12.8, IPT 32.1 ± 1.6, IPL 37.9 ± 2.4), with longilinear thoracic proportions (IT 72.7 ± 22.1, IA 2.1 ± 0.2), and with corporal volume in harmony with the skeletal development (IP 84.8 ± 4.5, IDT 11.0 ± 0.5, IDC 46.6 ± 12.8) (Table 4, Photographs 1 and 2).
Table 4 Zoometric indices of Oaxaca Mixteco criollo bulls.
| Indices | Variables | Mean ± SD | Min | Max | CV (%) |
|---|---|---|---|---|---|
| Ethnological | Cephalic | 48.5 ± 4.2 | 36.2 | 52.4 | 8.6 |
| Thoracic | 72.7 ± 22.1 | 40.0 | 141.7 | 41.2 | |
| Corporal | 79.9 ± 7.8 | 66.7 | 91.2 | 9.7 | |
| Lateral corporal | 94.4 ± 9.0 | 82.8 | 110.7 | 9.6 | |
| Anamorphosis | 2.1 ± 0.2 | 1.6 | 2.5 | 11.0 | |
| Pelvic | 84.8 ± 4.5 | 75.0 | 90.2 | 5.3 | |
| Milk producing aptitude | Dactyl-thoracic | 11.0 ± 0.5 | 10.2 | 11.7 | 4.4 |
| Dactyl-costal | 46.6 ± 12.8 | 28.6 | 62.5 | 27.4 | |
| Meat producing aptitude | Transverse pelvic | 32.1 ± 1.6 | 28.3 | 33.7 | 4.9 |
| Longitudinal pelvic | 37.9 ± 2.4 | 35.0 | 43.2 | 6.4 |
SD = standard deviation. CV = coefficient of variation.
The ICEF (48.5 ± 4.2) of the Oaxaca Mixteco criollo bulls is an indicator of an animal with narrow head, similar to the Casanare criollo (40.0 ± 4.8; Salamanca & Crosby, 2013a), but this index was lower to the one reported in limonero criollo (54.5 ± 4.2; Contreras et al., 2012). However, they enter in the classification of dolichocephalic animals, as the length of the head prevailed over the width of the head.
The IT of the bulls from this study (72.7 ± 22.1) was similar to that recorded in Santa Elena criollo (74.3; Cabezas-Congo et al., 2019), higher to the IT of Holstein cattle (62.0; Rodríguez et al., 2001), Barroso-Salmeco criollo (61.6; Jáuregui et al., 2014) and lojano criollo (59.6; Aguirre-Riofrio et al., 2019), and lower than that of Hereford cattle (93.0; Rodríguez et al., 2001). This index reflects the variations in the shape of the thorax; a higher value (more circular) indicates that the animal has aptitude for meat production, while a lower value (more elliptical) indicates that the animal has aptitude for milk production. Therefore, according to this index the Mixteco criollo cattle could be considered as a meat producing animal, with longilinear thoracic conformation and lightly elliptical.
The ICO of the Oaxaca Mixteco criollo (79.9 ± 7.8) was lower than that of the Casanare criollo (82.7; Salamanca & Crosby, 2013a), and higher than the ICO of the limonero criollo (76.2 ± 2.8; Contreras et al., 2012). These breeds, according to this index and the authors reporting on them, are classified as brevilinear, the same as the Mixteco criollo.
The ICL (94.4 ± 9.0) in the Oaxaca Mixteco criollo bulls was higher than in the Uruguayan criollo and in Hereford cattle (86.4 y 78.2, respectively; Rodríguez et al., 2001). In the first case, the authors could not determine whether the animals had an aptitude for milk or meat production, indicating that this situation could be clarified with a study on their productive and reproductive characteristics, whereas the Hereford breed is already known that is specialized in meat production. Therefore, according to the results obtained and considering that this index indicates that the lesser the value the more approximation of the animal to a rectangle shape, which is the predominant shape in the animals with aptitude for meat production (Parés i Casanova, 2009), the Oaxaca Mixteco criollo could be classified as an animal with tendency to the dual-purpose.
The IA obtained in these bulls (2.1 ± 0.2) was lower than the one reported in Santa Elena criollo (2.2; Cabezas-Congo et al., 2019), Hereford (2.3) and Holstein (2.8) (Rodríguez et al., 2001), and limonero criollo (2.38 ± 0.21; Contreras et al., 2012). According to Contreras et al. (2012), the IA determines the conformation of the individual because if its value is high (4.0 and 5.0) it makes reference to an animal for meat production and if it is low (2.5 and 3.0) to an animal with tendency to produce more milk than meat; nonetheless, according to the IA obtained in limonero criollo they determined that this breed has a biotype for the dual-purpose. Therefore, it could be considered that the Oaxaca Mixteco criollo fits this classification.
The IP of the Oaxaca Mixteco criollo (84.8 ± 4.5) was similar to the one reported in barroso-Salmeco criollo (84.7; Jáuregui et al., 2014), but lower than that in the lojano (92.9; Aguirre-Riofrio et al., 2019) and Uruguayan (130.1; Rodríguez et al., 2001) criollos. This index denotes the relationship between the width and length of the pelvis, indicating a pelvis that is proportionally wider rather than large or vice versa. A higher value is an indicator of a pelvis that is rather wide instead of long, which is observed in an animal with aptitude for the production of meat but not milk. The Mixteco criollo bulls had a pelvis which has wide rather than long, which suggests an aptitude for the dual purpose.
The IDT (11.0 ± 0.5), IDC (46.6 ± 12.8), IPT (32.1 ± 1.6), and IPL (37.9 ± 2.4) indices, which are used as indicators of the ability to produce milk or meat, were similar to those reported by Aguirre-Riofrio et al. (2019) in four biotypes of criollo cattle in the south of Ecuador: black (IDT 9.9, IDC 44.1, IPT 36.0, IPL 38.7), encerado (IDT 10.1, IDC 44.1, IPT 36.7, IPL 38.5), red (IDT 10.1, IDC 45.5, IPT 35.5, IPL 39.3), and Cajamarca (IDT 10.0, IDC 44.1, IPT 36.0, IPL 38.7). According to these indices, these authors classified the biotypes black, encerado, and Cajamarca as dual-purpose with a tendency for milk production, and the red biotype as dual-purpose with a tendency to meat production. Particularly, IPT and IPL indicate the meat-producing ability through the relationship between the width and length of the pelvis, which in turn is related to the height or corpulence of the animal, therefore, the Mixteco criollo showed an intermediate predisposition for the development of muscle tissue in this area that produces the most valuable meat cuts. Therefore, the Oaxaca Mixteco criollo cattle could be classified as a biotype for dual-purpose with a tendency to meat production.
