Texas Equine Veterinary Association

www.texasequineva.com • 10 Horse Evaluation A comprehensive way to evaluate a horse's condition during an on-farm visit is through the use of three assessment techniques to estimate body weight (BW), fat cover, and muscle tone. While BW is most easily measured using a platform livestock scale, this is frequently unavailable to clients. As such, researchers have developed equations using morphometric measurements to estimate BW in horses of various breed types with accuracy within 25 lb. (Martinson et al., 2014). The equation for stock type horses is listed below with the associated morphometric measurements: heartgirth circumference (g), length (l), height (h), and neck circumference (n). BW (lb) = (g 1.486 x l 0.554 x h 0.246 x n 0.261) /114 Fat cover is evaluated using the gold standard Henneke et al. (1983) scoring system. The scale ranges from 1-extremely emaciated to 9-extremely obese. This method uses tactile appraisal of 6 areas: crest of neck, behind the elbow, along the withers, ribs, crease of topline and tailhead. A score of 1–9 is assigned to each of the 6 regions and an average score is determined. While there is some debate amongst nutritionists, ideal BCS for performance horses is 5 and 6 for breeding horses. The final assessment tool for muscle tone was recently developed by Nutrena® in conjunction with their line of products containing Topline Balance™ technology. Instead of determining fat cover, like the Henneke BCS method, the Topline Evaluation System (TES) evaluates muscle development over the topline in three areas including: withers to mid-back, mid-back to croup, and hip-hindquarter. Evaluators then assign a grade A–D with A being ideal. While BCS and TES are subjective measurements and should be used with caution, their scores with BW estimates provide a comprehensive assessment of the horse's overall condition. To reduce variation in assigning BCS and TES scores, the same evaluator should be used every time, or multiple evaluators may average their assigned scores. Sample Collection Feed and hay samples collected for nutrient analyses must be representative of what is being fed to the horse. While this may seem obvious, it is easy to harvest samples that are not truly representative. Concentrate samples are the easiest to collect. If the client feeds a single commercial concentrate feed, the feed tag may be sufficient for the nutrient analysis. If further information is required, a sample should be collected from each shipment and/or lot. If the client mixes their own feed or adds multiple supplements to the diet, request that the client mix a typical meal for sampling. Approximately a half a cup is sufficient for a commercial laboratory to perform chemical analysis. Forage sample collection is a bit more complex in order to obtain a truly representative sample. For hay, a hay probe is the most accurate. The hay probe may be attached to a drill and used to take a core sample from square or round bales. As a general rule, one core per 10 bales should be collected and mixed for analysis. If a hay probe is not available, the client or consultant must take a representative sample by hand being careful to not sample the same location of every bale. Pasture samples may also be submitted for analysis if pasture turnout is common. Samples may be cut with scissors from 10–15 random locations within the pasture the horses are housed. A common trick among nutritionists in small to medium-sized pastures is to use a cut-out laminate tile (or anything similar; can get at a hardware store), stand randomly in the pasture and toss Figure 1. Example nutrient analysis of square baled coastal Bermuda grass hay (A) and a commercial concentrate feed (B) EXHIBIT A EXHIBIT B

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