Observations on the Hematology of Standardbred Horses in Training and Racing in Southern Italy

Abstract

Hematology may provide information about health states, performance, and fitness in horses. Hematologic data are available for horses in general, but they are mainly referred to Thoroughbred horses reared in their native English countries. Based on the assumption that age, sex, and management, as well as geographical location of the breeding sites may affect hematologic values, this study focused on the hematology of Standardbred trotters reared in southern Italy. Blood samples were collected from 100 apparently healthy trotters, reared in different horse stables. Hematologic parameters were screened, and microscopic evaluation for parasites in the red cells was performed. Descriptive statistics were estimated for the hematologic data, and variance analysis was performed by the general linear model procedure, including adjustment for gender and age. Standardbred trotters reared in southern Italy showed some peculiarities in their hematology compared with reference values. Young racing trotters (aged 3 and 4 years) reported a mean corpuscular volume value lower than other age categories and reference ranges; therefore, a less intensive training and a balanced nutritional plan were suggested to improve their welfare and performance. In conclusion, this study provides new reference values useful for veterinarians and equine technicians.

Introduction

The interest in Thoroughbred and Standardbred horse hematology has developed, and a considerable number of papers describing their normal values and related significance have been published. Neser [1] appears to have been the first to report that the red cell count of the racehorse was higher than that of other horses, and Steel and Whitlocka [2] first published a differentiated range between Standardbred and Thouroughbred horses reared in Australia.

Those authors seem to have been the first scientists who sorted data obtained from different breeds and proposed specific breed hematological profiles to owners and trainers that provided a better understanding of disease and poor performance problems. Presently, hematological profiles for specific breeds are already available [3], but the reported normal ranges are elicited from articles published mainly in America, Australia, or Great Britain [4]. Moreover, textbook reference ranges are produced by UK veterinary laboratories and are based mainly on thoroughbreds [5], so there is a lack of knowledge about hematology of Standardbred trotters reared in southern Italy.

As is well known, the horse's hematological profile is affected by different factors, and potential differences could be ascribed to genetics as well as to nutritional and environmental conditions [6]. A proper nutritional plan is essential for a good hematopoiesis, indeed, the first symptom associated with iron deficiency is a hypochromic, microcytic anemia [7]. Pritchard et al [8] stated that the adaptation of working horses to hot climate and endurance work from an early age influenced their hematological and biochemical basal ranges. In the same way, Tateo et al [9] demonstrated that yearling trotters, undergoing a particularly training program, showed changes in their hematological profiles as a consequence of the tested feeding and training plans.

Management has important effects particularly on hematology of race horses, which are usually involved in hard training programs and travel to reach distant racetracks before racing. In trotters, in fact, overtraining syndrome caused an increased hematocrit and lower value of mean corpuscular volume (MCV) and mean corpuscular hemoglobin (MCH) [10]. Also, transport, housing systems, and feeding techniques could lead to diseases that modify horses' hematological and behavioral profile [11], [12], [13].

Reference hematological parameters are often used for assessing the welfare condition and stress level of animals [14] but also the level of fitness [15]. Assuming that the red blood cells are strongly influenced by the lifestyle to which horses are subjected, the aim of this study was to report the normal values of erythrocytes for southern Italian Standardbred trotters in racing and training, in order to understand their welfare conditions. Moreover, the influences of age and gender on Standardbred hematology were also investigated, considering the previous work of Adamu et al [16], who found a relationship between poor performance and age in endurance horses; and Cywinska et al [17] reported a gender difference during exercise.