July 7, 2000

Breeding mares?
Check their body condition!

By Mike Barnett
Editor

Fat mares won’t breed. Fat mares have trouble foaling. That’s the dogma much of the horse industry has suffered through for years. And it’s simply not true, according to Dr. Don Topliff, professor and head of the Agriculture Division at West Texas State University.

“One of the myths that has somehow crept into horse reproduction is this idea that mares ought to be thin at the beginning of the breeding season, that you ought to feed them to gain weight. Now that works for sheep really well,” Topliff said recently at the Western Rolling Plains Mare and Foal Clinic in Guthrie. “But what I’m here to tell you is that’s not what we need to do. I don’t know where the myth came from, but I’m here to tell you it’s a myth.”

One of the most important aspects of getting mares bred is body condition.
Topliff said all females—humans, cows, sheep, sows—need a certain amount of body fat before they will cycle and reproduce normally.

“And if we don’t have that fat, then it’s just not going to work,” he said.

To that end, Texas A&M researchers looked at how body condition affects reproduction in mares back in the 1980s. A body condition scoring system for cattle, that showed a big correlation between body condition and reproductive rates, had already been developed. A similar system was developed for mares.

Body Condition Scores (BCS) range from 1 to 9. BCS 1 is extremely poor, emaciated, near death. BCS 1 to 3 are seldom seen if the horses have any kind of management at all. BCS 4 was where many managers think their mares should start the breeding season. Anything above a BCS 7, many breeding managers thought, was simply too fat to breed.

A number of studies, in fact, have shown just the opposite. The first involved 32 pregnant mares divided up into four groups of eight.

The first group, foaled at a BCS 4, the body condition advocated by many breeding farms as ideal, and maintained at a BCS 4 for 90 days postpartum, had a 50 percent conception rate.

The second group, foaled at a BCS 4 and fed to gain weight to a BCS 7 by 90 days after they foaled, had 100 percent conception rate.

The third group, foaled at BCS 7 and then allowed to lose weight during early lactation to a BCS 4, resulted in a 62 percent conception rate.

And the fourth group, foaled at a BCS 7 and maintained at a BCS 7, had a 100 percent conception rate.

“At first blush, you look at this and say, ‘That’s true. You bring them in thin and feed them to gain weight. No problem’,” Topliff said, referring to the second group that foaled at a low score and were fed to a high BCS. “Now, the rest of the story. To get them to a Body Condition Score of 4 to 7, in 90 days, took an average of 40 pounds of feed per day.

“How many of you want to try to manage a herd of broodmares and feed that amount of feed?” he asked. “The risk of doing that in terms of colic, founder, all those kinds of things, is not something most people are willing to accept.

“Even though we can achieve those reproductive rates going from low to high, it’s a very difficult management situation. And it’s not necessary. Because if we’ll just bring them in at a 7 to begin with and maintain them there, we can achieve the same kind of reproductive rates.”

A field trial involving four of the largest commercial horse breeding farms in the state confirmed the first study’s results. Horses were scored as they came into the farms and results tabulated. They showed:

• 158 mares, BCS less than 5, 71 percent pregnancy rate.
• 667 mares, BCS 5 to 7, 92 percent pregnancy rate.
• 102 mares, BCS greater than 7, 96 percent pregnancy rate.

Also, it took 2.8 heat cycles per conception with those mares BCS 5 or less, compared to 1.4 cycles per conception of mares with BCS 5 to 7 or greater than 7.

“So our standard recommendation is, for mares that are going to be nursing a foal, we’d like for them to show up at the breeding farm at a 7 or 7 1/2,” Topliff said. “For open mares or maiden mares, they’re not undergoing that kind of stress, we can back that off to a 6 or a 6 1/2.

“But, if you want the best chance of getting your mare in foal, don’t send her to the breeding farm in a body condition score of 5, whether she’s open, maiden, nursing a foal,” he continued. “It doesn’t matter. You don’t have any insurance. There’s no room for error.”

Body Condition Scores

1. Poor. Animal extremely emaciated. Spinous processes, ribs, head and hooks and pins projecting prominently. Bone structure of withers, shoulders and neck easily noticeable. No fatty tissue can be felt.

2. Very Thin. Animal; emaciated. Slight fat covering over base of spinous processes, transverse processes of lumbar vertebrae feel rounder. Spinous processes, ribs, tailhead and hooks and pins prominent. Withers, shoulders and neck structures faintly discernible.

3. Thin. Fat built up about halfway on spinous processes, transverse processes cannot be felt. Slight fat covering over ribs. Spinous processes and ribs easily discernible. Tailhead and individual vertebrae cannot be visually identified. Hook bones appear rounded, but easily discernible. Pin bones not distinguishable. Wither, shoulders and neck accentuated.

4. Moderately Thin. Negative crease along back. Faint outline of ribs discernible. Tailhead prominence depends on conformation, fat can be felt around it. Hook bones not discernible. Wither, shoulders and neck not obviously thin.

5. Moderate. Back level. Ribs cannot be visually distinguished but can be easily felt. Fat around tailhead beginning to feel spongy. Withers appear rounded over spinous processes. Shoulders and neck blend smoothly into body.

6. Moderate to Fleshy. Slight crease down back. Fat over ribs feels spongy. Fat around tailhead feels soft. Fat beginning to be deposited along the sides of withers, behind the shoulders and along the sides of the neck.

7. Fleshy. Crease down back. Individual ribs can be felt, but noticeable filling between ribs with fat. Fat around tailhead is soft. Fat deposited along withers, behind shoulders and neck.

8. Fat. Prominent crease down back. Difficult to feel ribs. Fat around tailhead very soft. Area along withers filled with fat. Area behind shoulder filled in flush. Noticeable thickening of neck. Fat deposited along inner buttocks.

9. Extremely Fat. Extremely obvious crease down back. Patchy fat appearing over ribs. Bulging fat around tailhead, along withers, behind shoulders and along neck. Fat along inner buttocks may rub together. Flank filled in flush.