Researchers weigh in over weight formulas for Warmblood and Icelandic horses

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Icelandic Horses in Iceland.
Icelandic Horses in Iceland. © Nick Hodgson

Some simple measuring formulas proved accurate in estimating the weight of Icelandic and Warmblood horses, researchers report.

Rasmus Bovbjerg Jensen and his colleagues, writing in the journal Acta Veterinaria Scandinavia, said some formulas using only heart girth, or heart girth and length, can be used to estimate the body weight of the two breeds as efficiently as more complex formulas using four measurements.

The researchers used 43 Icelandic and 38 Warmblood horses for their study.

They measured the height of each animal at the withers, neck length, half the neck length, neck circumference, umbilical circumference, two different heart girths, as well as two different body length measurements for use in a variety of formulas that can be used to estimate body weight.

A depiction of all the measurements taken. NC: neck circumference; L1: length from point of shoulder to point of buttock; L2: length from point of elbow to point of buttock; G1: heart girth from top of the withers; G2: heart girth from slope of the withers; U: umbilical girth; H: height at withers. All morphometric measurements were obtained in centimetres

The horses were weighed on scales to determine the accuracy of each formula. They also took the cresty neck scores and body condition scores of each horses using both the 0 to 5 and the 1 to 9 systems, and undertook some blood work.

In general, the formulas proved quite accurate, with even some of the simplest ones performing well.

The authors pointed out that, while scales are the most accurate way of obtaining the weight of a horse, they are often not accessible.

A horse’s weight is commonly visually estimated, but this has been found to be less accurate than using a formula or a weight tape, which uses only the girth circumference.

Body-weight formulas can be more complex, but have also been suggested to be more accurate than a weight tape, and several have been developed over the years.

However, conformational differences between various breeds may influence the accuracy of the respective formulas.

“Therefore, it is important to evaluate different body weight formulas and their suitability for use in different breeds.”

For their study, a total of 10 formulas were applied to each horse, then compared with the results given by the scales. The list of formulas, and the way in which weight is calculated using each method, appears in the table below.

The different body measurements of horses and formulas used to estimate body weight of horses.
The different body measurements of horses and formulas used to estimate body weight of horses. G1: heart girth from top of the withers; G2: heart girth from slope of the withers; L1: length from point of shoulder to point of buttock; L2: length from point of elbow to point of buttock; U: umbilical girth, H: height at withers; NC: neck circumference.

Of the simple formulas using only heart girth circumference, the formula from Marcenac and Aublet and Willoughby did better — with a higher concordance correlation coefficient — than the formula from Staun for the two breeds used in the study.

Of the formulas using two body measurements, the formula from Carroll and Huntington was the most accurate, followed by the formula from Martin-Rosset for the Icelandic horses.

The more complex formulas with four body measurements also performed well, they said.

However, there were also formulas for which the deviation from the measured body weight was relatively large and these cannot be recommended to be used for the two breeds, they said.

In conclusion, they said that some simple and more complex formulas can be used for Icelandic horses even though they are not developed for this breed.

They said the simple formulas that proved accurate could be applied to weight tapes and used to estimate the body weight of both Icelandic and Warmblood horses.

Blood work carried out in the study show that plasma concentrations of leptin and insulin were higher for the Icelandic than the Warmblood horses, probably reflecting higher body fat content as suggested by the differences in body condition scores.

The full study team comprised Jensen, from the Norwegian University of Life Sciences; and Lucca Louise Rockhold and Anne-Helene Tauson, from the University of Copenhagen.

Jensen, R.B., Rockhold, L.L. & Tauson, A. Weight estimation and hormone concentrations related to body condition in Icelandic and Warmblood horses: a field study. Acta Vet Scand 61, 63 (2019) doi:10.1186/s13028-019-0498-5

The study, published under a Creative Commons License, can be read here

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