When assessing the suitability of a horse’s diet, the first factors to consider are body condition score (BCS) and body weight (BW). Body condition scoring is a universal and scientific method of evaluating a horse’s body condition, regardless of individual characteristics.
The most commonly used BCS system is the Henneke system, which is a 9-point scale. Areas where the equine body deposits fat are evaluated and scored individually, and then used to assign an overall score. BCS can be a useful way to assess the suitability of energy content in the diet (and thus overall energy balance) based on the overall score:
Score 1-3: Energy deficit.
Score 4-6: Energy requirement.
Score 7-9: Energy excess.
BCS should be assessed every 2-4 weeks, or even weekly in the winter, and should be monitored following diet changes so that the diet can be tweaked to prevent major weight loss or gain (Gorniak et al, 2020).
Body weight is important as many nutritional requirements are based on a function of the animal's weight. While using a livestock scale is the most accurate method of learning your horse’s body weight, this is not always an accessible option. Fortunately, mathematical formulas have been developed which can estimate body weight based on 2 measurements: heart girth and body length. The Carroll and Huntington (1988) equation predicts BW of light horse breeds with the best accuracy of available formulas (Jensen, Rockhold, and Tauson, 2019):
BW (kg) = [heart girth (cm) x heart girth (cm) x body length (cm)]/11877
To calculate your horse’s BW, measure their heart girth from the slope of their withers, and around their body. Then measure from the point of the shoulder to the point of the buttocks. This can be done with a soft measuring tape, or first with a string and marker, and then measured. Weight tapes can also be an appropriate tool to estimate BW among individual animals, keeping in mind that height-specific weight tapes are best (Jensen, Rockhold, and Tauson, 2019).
Due to conformation differences between horses, BCS and BW should always be used together to assess the diet's suitability. Keeping a record of your horse’s BCS and BW in a record book or file is also a great strategy to track changes over time!
REFERENCES
Carroll, CL., Huntington, P. 1988. Body condition scoring and weight estimation of horses. Equine Veterinary Journal 20(1): 41-45. https://doi.org/10.1111/j.2042-3306.1988.tb01451.x
Gorniak, W., Wieliczko, M., Soroko, M., Korcynski, M. 2020. Evaluation of the Accuracy of Horse Body Weight Estimation Methods. Animals 10(10): 1750. https://doi.org/10.3390/ani10101750
Henneke, DR., Potter, GD., Kreider, JL., Yeates, BF. 1983. Relationship between condition score, physical measurements and body fat percentage in mares. Equine Vet. J 15(4):371-372. https://doi.org/10.1111/j.2042-3306.1983.tb01826.x
Jensen, RB., Rockhold, LL., Tauson, AH. 2019. Weight estimation and hormone concentrations related to body condition in Icelandic and Warmblood horses: a field study. Acta Veterinaria Scandinavica 61: 63. https://doi.org/10.1186/s13028-019-0498-5
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