A new owner-friendly horse scale to identify the easy keepers from the hard keepers has been developed by researchers at the University of Delaware.
Horses with different metabolic tendencies are anecdotally referred to as “easy” or “hard” keepers. Easy keepers tend to gain weight easily while hard keepers require extra feed to maintain condition. There is also a group sometimes referred to as medium keepers.
Both easy and hard keepers carry a managerial and financial burden which can be a dissuading factor for people shopping for a horse. For some owners, it may mean separating easy keepers from other horses to keep them on tighter rations, while hard keepers may require additional food rations.
Alexa Johnson and Amy Biddle, in a study just published in the journal Animals, described their research into energy intake and body condition in horses to develop a standard Equine Keeper Status Scale (EKSS) for assigning “keeper” status.
The scale was developed and validated based on data gathered from 240 horses.
Estimates of dietary energy intakes and requirements to achieve the optimal body score of 5 on the nine-point Henneke scale were used in developing the scale.
Thriftiness in horses, they said, has been associated with more efficient nutrient harvesting in digestion, absorption and/or utilization, but the relative contribution of the gut microbiome to each animal’s metabolic tendency is not well understood.
With this in mind, they also looked into the composition of the microbial families present in the guts of the study horses based on their position on the EKSS, and then compared the differences based on the metabolic tendencies of each group.
Based on molecular-based fecal analysis in 73 horses, the researchers found differences in the number of species, and their distribution and ratio.
Easy keepers had more Planctomycetes and fewer Euryarcheaota, Spirochaetes and Proteobacteria than the hard keepers, indicating functional differences in nutrient harvesting between groups.
“Understanding microbiome differences between easy, medium and hard keeper horses points to potential microbial roles in these metabolic tendencies.”
The EKSS can be used by owners to accurately assess their horses’ metabolic tendencies and make improved feeding decisions to meet their horses’ needs, they said.
And owners who think it is easy to identify their easy keepers from their hard keepers might need to think again. Sixty percent of owners’ characterizations disagreed with the EKSS assignments of their horses.
The EKSS was developed using horses of varying workload, age, sex, diet and breed. It is not for use in donkeys and mules as they have much better feed conversion ratios compared to horses, and their fat distribution is significantly different.
The first stage of using the scale involves calculating the difference in body condition score of a horse from the ideal score of five. The second phase involves calculating the megacalories required to achieve an ideal score. The third formula involves calculating the required dietary energy intake to achieve the ideal score of five.
The result classifies horses as either easy, medium or hard keepers, but there are also seven levels within the scale to provide greater resolution and precision.
Johnson and Biddle said the EKSS tool was designed to be easy for horse owners, veterinarians and researchers to learn and use with minimal technical skill, equipment, or cost. Its groupings maintain the current verbiage of ordinary horse owners.
In scoring the horses in the study, the researchers ensured that field-based methods were used. Equine body weight was obtained using a weight tape. Body scoring was done by two people, and a commercial online equine nutrition calculator (www.FeedXL.com) was used to estimate the dietary composition of individual equine diets.
Equine activity level was determined by the work level described by the owners, and classified as ‘no work’, ‘light’, ‘moderate’, ‘heavy’, and ‘very heavy’.
Johnson and Biddle described the current definition of equine keeper status as ambiguous and poorly characterized within the equine community.
“The current ideology behind the keeper status is the combination of equine body condition and how readily the animal maintains weight to determine how the horse should be fed.”
Overweight horses that can easily maintain a body condition score of six or more are “easy keepers” and underweight horses that easily maintain a score of four or less are “hard keepers”; and both groups struggle to maintain or achieve an ideal score of five. A third classification, “medium keepers”, describes horses that can easily maintain a score of five.
“As a result of the ambiguity of equine keeper identification and the pressure of social biases, easy keeper and hard keeper horses are fed two drastically different diets.”
To reduce weight gain, easy keepers are often fed restricted and depleted diets, and to induce weight gain hard keepers are often fed extremely energy-dense diets.
“Both of these feeding methods are antithetical to the anatomical design of the equine gut and can result in gut dysbiosis,” they said.
The EKSS tool should alleviate confusion and help with feeding management for all horses.
Turning to the differences in the gut microbiome between easy and hard keepers, the researchers said it was unclear within the study population if these differences were the consequence of different feeding methods.
The lower diversity seen in the easy and hard keepers, as assessed under the EKSS tool, may indicate that these gut communities are less stable and have a greater sensitivity to dysbiosis than the medium keepers.
However, a controlled study to reduce diet, management and equine factors is needed to validate microbiome differences associated with EKSS tool and the keeper status of horses.
Johnson, A.C.B.; Biddle, A.S. A Standard Scale to Measure Equine Keeper Status and the Effect of Metabolic Tendency on Gut Microbiome Structure. Animals 2021, 11, 1975. https://doi.org/10.3390/ani11071975