Body Condition and Reproductive Performance in Mares

A lot of research has been done on the nutrition requirements of mares.  There are recommendations for proper nutrition for maintenance, for early gestation, mid-gestation, late gestation, early lactation, mid-lactation, late lactation, and for levels of activity or work.  Since this article focuses on reproduction and breeding, we won’t discuss the needs for a working horse.

A tool that horse breeders can use when making nutrition decisions is Body Condition Scoring (BCS).  A nine-point scale is used in horses that ranges from a very thin, walking sack of bones that would score 1 on the scale to a roly-poly, extremely fat horse scored a 9 that can roll downhill faster than she can run.  Extremely fat horses have other problems, including physiological disorders resulting from hormonal imbalances and abnormal endocrine function.  Body condition scores give a clear picture of just where a horse fits on that scale, and give a good indication of whether a mare will re-breed on schedule, or will be delayed.

Consider these points.  In a study done at Texas A&M University:

·  Mares foaling in thin condition had poor reproductive performance during rebreeding, even when the ration was balanced to meet early lactation needs.

·  Increasing the energy fed to thin mares during lactation improved rebreeding efficiency, but increases the risk of colic and costs a lot more.

·  Fat mares that foaled used stored body fat for efficient reproduction and lactation even if they lost weight after foaling. They did not have problems during foaling and had high rebreeding efficiency.

·  Open mares, maiden mares, and foaling mares entering the breeding season in moderate or higher condition achieved or maintained higher reproductive efficiency than mares scored as thin.

·  Increasing body condition above moderate levels before the breeding season did not impair reproductive performance, but was generally of no benefit unless the mares were losing weight during the breeding season.

In general, mares with moderate or higher energy stores cycled earlier, had higher pregnancy rates, had fewer cycles per conception, and sustained more pregnancies than thin mares.  With that in mind, mares should enter the breeding season in a moderate condition (BCS 5), be maintained in moderate to fleshy condition (BCS 6 to 7), and foal in fleshy condition ( BCS 7).  Don’t let the mare get to a BCS over 8 at any time.

Since mares in early lactation are using more energy to produce a high volume of milk than they can metabolize from feed, it makes sense that a mare that has some energy reserves will recover from parturition more quickly and have fewer problems than a thin mare that has to provide milk for a foal, then rebuild body tissues and reserves to reach the point where she is physiologically ready to rebreed.

There are six places on a mare to evaluate body condition.  These are the neck, withers, loin, tailhead, ribs, and shoulder.  The BCS evaluation is a blend of visual cues and light palpation of fat deposits in these areas.  To use an example of what a moderate condition score (BCS 5) is, consider the following descriptions of the six areas:

·  Neck – Blends smoothly into the body

·  Withers – Are rounded over the spinous processes

·  Loin – Back is level

·  Tailhead – Fat around the tailhead is beginning to feel spongy

·  Ribs – Cannot be visually distinguished but can easily be felt

·  Shoulder – Blends smoothly into the body

For a more complete description of the Body Condition Scoring System for horses, the NCSU factsheet ”Body Condition Scoring: A Management Tool for the Broodmare Owner” give a complete description of what a horse owner should look for in each of the six areas of evaluation for body condition.  It can be downloaded from http://www.cals.ncsu.edu/an_sci/extension/horse/PDF Files/Mare and Foal Nutrition BCS FACT SHEET.pdf.

Body Condition Scoring is not just for use on broodmares.  Any horse owner can learn to use this tool to decide when adjustments to the ration should be made.  Keeping the horse in moderate condition – remember that is a BCS 5 – helps the owner or manager reduce or avoid nutrition-related problems.