Hematological and Biochemical Reference Values in the Donkey (Equus asinus) in Mexico

Introduction

The majority of hematological and biochemical values in donkeys have been researched in animals that live in countries where they are kept as pets [1,2] or in welfare organizations and not used for hard work. In many parts of the world where poverty still prevails such as in Mexico, donkeys are an indispensable aid for many poor people. They carry heavy loads of wood, water, and other items; take children to school and their owners' home after they have sold their products at markets. They receive minimal care and the food they get is usually of inferior quality [3]. The most frequent pathological conditions found in these working donkeys are caused by intestinal parasites and skin wounds due to ill-fitting tack. It has been suggested that normal blood values for the different animal species should be established in the diagnostic laboratories of areas where they live, as it cannot be assumed that they are the same in all regions of the world. The present study was undertaken with the aim of establishing blood values in donkeys on the high plateau of Mexico at an average altitude of 2,200 to 2,600 meters above sea level.

Material and Methods

Blood samples were taken from 48 clinically healthy donkeys of different genders that lived in the states of Mexico (altitude 2,600 m above sea level) and Guanajuato (altitude 2,008 meters above sea level). Their body condition was between 3 and 4 in a grading system of 1 to 5, 1 being very poor and 5 excellent; they had been periodically dewormed. The average age of the animals was 7.1 ± 4.6 years.

The donkeys from the State of Mexico had been collected from different farmers for a nutritional trial carried out at the School of Veterinary Medicine at the Autonomous University of State of Mexico and had not been working at the time of sampling or for several months before. Their food consisted of 85% maize stover, 15% alfalfa hay, some maize and a commercial concentrate for horses. The group from Guanajuato was on pasture during the day and received some alfalfa hay and maize stover when they returned home in the evenings. They had equally not been working for several months. Blood was collected in Vacutainer™ tubes, one with the anticoagulant EDTA and the other without. Hematocrit was determined by microhematocrit [4,5] . Red and white blood cells were counted with a Neubauer hematocitometre. Plasma proteins were determined with a refractometer [4,5]. Wright’s stain was applied for white cell counts. For biochemical determinations, colorimetric techniques were used. Reagents were obtained from Diagnostic Chemical Ltd (USA). In order to obtain reference values, the methodology recommended by Ferver [6], was followed. The statistical evaluation was done according to SAS [7]. The time between collecting the blood sample and processing it in the laboratory was not more than 4 hours.

Results and Discussion

The results are presented in Table 1, Table 2, Table 3 and Table 4. The values for hematrocrit (PCV), plasma proteins, red blood cells, and Mean Corpuscular Volume (MCV) obtained in this study are similar to those referred by Zinkl et al., [1], Hill [8] and Nayeri [9] for adult donkeys. French and Patrick [2] reported lower fibrinogen values (2 - 4 g/L) than those found in the present study (1 - 6.8 g/L), which may be explained by the fact that they worked with younger animals (less than 2 years old).

Leukocyte values are comparable to those reported by Zinkl et al., [1], who worked with 166 adult donkeys, but differ from those reported by French and Patrick [2] presumably for the same reasons given above. Values for albumin (26 - 28 g/L) in the present study are comparable to those of other authors (Hill [8], French and Patrick [2], Zinkl et al., [1]). This suggests that the values for albumin are independent of age, sex, nutrition, and geographical site.

Aspartate amino transferase (AST) values (197 - 612 IU) are similar to those reported previously by Paredes et al., [10] (358 - 504 IU) and Aluja et al., [11] (82 - 496 IU) in Mexico. The values of Paredes et al., [10] and Aluja et al., [11] were taken in working donkeys before they started their daily work, which may account for the differences. In contrast, the values reported by French and Patrick (59 - 199 IU) [2] are lower, however, they belong to donkeys less than 2 years of age.

The enzyme gamma glutamyl transferase is useful for the detection of bile duct pathology. The values in the present study (21 - 177 IU) are higher than those of French and Patrick [2] (8 - 49 IU), but these authors do not specify which method was used to determine this analyte. It must be remembered that Fasciola hepatica is a frequent parasite in many areas of Mexico, a fact that may account for these higher values, even if the donkeys did not show clinical signs. Only the minimal values of glucose found in this study (2 mmol/L) agree with those of Aluja et al., [11] and French and Patrick [2] for adult animals.

The creatinine ranges obtained are similar to those referred by French and Patrick [2] (1.89 - 6.18 μmol/L).

Calcium and phosphorus values determined in the present study are similar to those of Zinkl et al., [1] and Mori et al., [12], however, Hill [8] informs of wider ranges, which may be explained by differences in climates, geographical areas and number of animals examined (n=16), as he worked in Zimbabwe and his donkeys were actually working.

The ranges of potassium, sodium and chloride are similar to those referred by other authors [2,8,10,11]. The bicarbonate values determined in this study differ from those given by Aluja et al., [11] who determined them in working donkeys, a fact that will cause changes in this analyte.

Conclusions

The majority of the blood values in donkeys investigated in this study are comparable to those of other authors, despite the fact that they were done in different parts of the world. However, certain differences within the ranges of some of the analytes prove the need to establish reference values specifically within each of the in regions where donkeys work. This study shows that reference values for horses should not be used to interpret blood values in donkeys (Table 4 and Table 5).

Acknowledgements

The help of Astrid Karina Villalobos in obtaining the blood samples is gratefully acknowledged. We are grateful to Dr. Octavio Carranza from the School of Veterinary Medicine and Zootecnics of the Autonomous University of State of Mexico and to Mrs. Sikman de Romero of Guanajuato, for letting us use their donkeys for this study. We also acknowledge the help of Dr. Anne Pearson, who reviewed the manuscript and gave valuable suggestions and Mrs. Isabel Aguilar for excellent secretarial work.