Beyond scoring systems: usefulness of morphometry considering demographic variables, to evaluate neck and overall obesity in Andalusian horses.

Morphometry has proven to be a useful tool, both for the clinician and horse owners, for evaluating the body condition in equids due to its objectivity, easiness and capacity for detection of important metabolic disturbances. However, limited information is available on the use of morphometric ratios to characterize regional and overall adiposity and much less about their application in different genders, ages and horses with different levels of obesity. The objectives were to evaluate body and neck absolute measurements and ratios; factors affecting them such as the influence of gender, age, appearance of the neck crest and overall body condition and; relationships among these measurements. A total of 154 Andalusian horses classified according to their gender, age, body score status and cresty neck condition were evaluated in this cross-sectional study. Two evaluators assigned a body condition score (BCS, 1 to 9) and a cresty neck score (CNS, 0 to 5) to each horse. Horses were divided into males and females; young (2 to 5 years) and adults (6 to 15 years); obese (BCS⩾7) and non-obese (BCS<7); cresty neck (CNS⩾3) and non-cresty neck horses (CNS<3). Morphometric measurements (cm) included were: height at the withers (HW); body length (BL), girth (GC) and waist (WC) circumferences; neck length (NL); three neck circumferences (NCs), over the first (NC25%), the second (NC50%) and the third part (NC75%) of the NL and neck crest height (NCH). These measurements were also used to calculate the following ratios: GC : HW, WC : HW, GC : BL, WC : BL, NC25% : HW, NC50% : HW, NC75% : HW, NC25% : BL, NC50% : BL, NC75% : BL, NC25% : NL, NC50% : NL, NC75% : NL, NC25% : NCH, NC50% : NCH and NC75% : NCH. The results showed that most of the absolute measurements and ratios were greater than those described in other light breeds. In addition, most neck ratios were higher (P<0.050) in males than in females, however, all body ratios were greater (P<0.001) in females. Among the absolute measurements, WC in obese horses and NC25% and NC75% in cresty neck horses highlighted as higher. Either GC : HW or WC : HW and NC75% : BL were alternative surrogates for the appraisal of overall and regional adiposity in Andalusians. Several interactions were observed between the gender and adiposity scoring systems affecting the morphometric evaluation. This study establishes absolute morphometric measurements and ratios in Andalusian horses. It also highlights the variability of morphometric values and how the outcome of these can be influenced by demographic variables and the breed analyzed. Further studies are necessary to set morphometric reference values in other breeds.

Endocrine, morphometric, and ultrasonographic characterization of neck adiposity in Andalusian horses.

Equine metabolic syndrome (EMS) can be diagnosed by hormonal measurements; however, it would be important to find simpler measurements that allow easy identification of affected or at risk individuals. In horses, the dorsal neck region is one of the most frequent anatomical sites for fat deposition and neck obesity has been linked to EMS. The aim of this study was to evaluate the association of hormonal markers of obesity (leptin) and insulin resistance (insulin) with morphometric and ultrasonographic neck measurements in Andalusian horses. Plasma leptin and insulin concentrations were measured by RIA in 127 Andalusian horses. Neck circumferences (NC) were measured at 3 equidistant locations at 25%, 50%, and 75% of neck length (NC-25%, NC-50%, and NC-75%). At the same 3 locations, subcutaneous fat thickness (SFT-25%, SFT-50%, and SFT-75%) was measured ultrasonographically. In the population under study, a tendency to adiposity was confirmed by the elevated plasma leptin levels (7.47 ± 5.03 ng/mL). However, plasma insulin concentrations (4.05 ± 3.74 µIU/mL) were within normal range in most horses. Our results indicate that NC showed significant sexual dimorphism and did not correlate well with hormonal measurements. Ultrasonographic assessment of fat thickness at the base of the neck (SFT-75%) was significantly correlated with both plasma leptin and insulin and did not show differences between males and females. Thus, in the search for a single objective parameter which can be used in large populations, SFT-75% is a potential candidate and may be a meaningful parameter to predict EMS.

Clinical Research Abstracts of the British Equine Veterinary Association Congress 2015.

REASONS FOR PERFORMING STUDY: Andalusian horses have been proposed as a breed predisposed to equine metabolic syndrome (EMS) phenotype [1] because they are prone to exhibiting regional, generalised adiposity and tendency to laminitis [2]. Insulin dysregulation represents the main pathophysiological cause for all the features of EMS, however there are no epidemiological studies in this breed. OBJECTIVE: To assess insulin dysregulation through insulin proxies in Andalusian horses with different levels of obesity. STUDY DESIGN: Cross-sectional study. METHODS: One hundred and sixty-four Andalusians (78 stallions and 86 mares, 2-15 years) were scored for overall (body condition score, BCS) and neck (cresty neck score, CNS) adiposity. Grain concentrate was withheld for 12 h before sampling. Blood samples were collected between 06.00-10.00 h for basal glucose, insulin concentrations, RISQI and MIRG proxies calculation. Conditions were defined as: obese horses (Ob), BCS ≥ 7; cresty neck horses (CN), CNS ≥ 3; hyperinsulinaemia, insulin ≥20 µu/ml; low insulin sensitivity, RISQI<0.32[mu/l](-0.5) and increased insulin secretory response, MIRG>5.6muinsulin (2)/[10.l.mgglucose]. Regarding BCS 2 groups were created: Ob and non-Ob. These groups were subdivided depending on CNS: with CN and without it (nonCN). Ob-nonCN group (n = 2) was excluded for the statistics due to the low number of horses. RESULTS: Of the horses studied, 26.8% were Ob-CN, 42.1% were nonOb-CN and 31.1% were nonOb-nonCN. Ob horses presented higher insulin levels (P = 0.034) and lower RISQI values (P = 0.019) than all nonOb horses. When CN was considered, only RISQI was lower (P = 0.015) in Ob-CN group respect to nonOb-nonCN, however nonOb-CN group does not differ from the other 2 groups. Furthermore, the percentage of Ob-CN horses with hyperinsulinaemia (2.3%), abnormal RISQI (4.5%) and MIRG (9.1%) was very low. CONCLUSIONS: These results suggest that in Andalusians, increased adiposity was not clearly associated to insulin dysregulation and, similar to human beings, may coexist as a metabolically healthy but obese phenotype. Ethical animal research: Ethical University Committee approved all the procedures and owner informed consent was obtained. SOURCE OF FUNDING: None. Competing interests: None declared.