Soybean meal

[Doc-t]

Hi @Kerry – What is a “mug?”

The minimum amount is 1 pound of Soybean Meal (SBM) (measured on a scale) daily for a 1200-pound horse. That’s 454g SBM for a 545kg horse. This assumes feeding forage (pasture and hay) at about 1.5% to 2.0% body weight (average at 1.75%) and roughly 10% protein. Of course, you can’t measure the amount of pasture they eat, and the protein of hay and pasture varies, but if the horse is losing body fat coming out of winter, carefully increase the hay to add the sugar and fat needed to add body fat.

Each pound of SBM has about 175g of absorbed protein, and each pound of 10% protein forage has about 23g of absorbed protein. Feeding 1.75% of 1200 pounds in forage (21 pounds) means the total forage protein will be 483g. 483 + 175 = 658g of total protein.

I chose 1200 pounds because it is so divisible: 100, 200, 300, 400, and 600, or any combination, such as 700, 800, 900, 1000, etc. So, if your horse weighs 800 pounds, feed 2/3rds (0.67) of the above numbers: 14.1 pounds of forage and 0.67 pounds of SBM.

The goal is to feed 0.5 to 1.0 grams of protein per pound of body weight. Therefore, a 1200-pound horse would need between 600 and 1200g of protein daily. Feeding 1 pound of SBM plus 21 pounds of forage will fulfill the minimum requirement of 600g.

You can add more SBM and remain within the recommended goal. For example, if the 1200-pound horse still eats 21 pounds of forage but eats 2 pounds of SBM, the total will be 833g; with 3 pounds of SBM, the total will be 1008g. These are all within the accepted range. Only 1 pound of SBM per feeding is recommended (based on human literature converted to the size of horses), with 3 to 4 hours between feedings.

26-year-old horses often show more fat and muscle loss coming out of winter than younger horses. Adding hay and increasing SBM now will help turn this around. Caution is needed as the grass grows because the horse may become too fat. This is because he is eating more sugar than is required, which may cause him to convert added protein into sugar – a paradox I have discussed in podcasts, etc. Therefore, as he gains body condition through the summer, reduce the hay until the grass stops growing (late fall). Then, add back enough hay to maintain his condition through the winter. Keep the SBM volume high until his muscle returns and his hooves and hair look great. Then, you can reduce the SBM to the minimum amount, which you may find is 1 pound twice daily.

Your aim is to keep the horse with enough body fat and muscle to remain healthy. Each horse is different, and with age comes more difficulty in doing this. Constant adjustments are required as the seasons change. However, increasing the amount of SBM you feed is an excellent way to maintain the muscles he needs to thrive at his age. Doc T

[Kerry]

Thanks @Doc-t sorry this is my mug – about 2 cups I think. I’ll get some scales!😁

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[Doc-t]

Thanks! 🤠

[Kerry]

Hi Doc T, sorry but I still can’t work out the maximum SBM our horse could have. He’s around 650kg and on the basis of 2% forage I think he could have around 541g of SBM per day. Is that the minimum and could we give him more than 541g and what would be the maximum SBM? Could we also give him Coolstance with SBM if he doesn’t maintain his weight this summer? Many thanks

[Doc-t]

2% of 650kg (1433 pound) body weight = 13kg of forage (pasture and hay).

Let’s assume the hay is 10% protein. 10% of 13kg = 1.3 kg of protein. But only half of that protein is absorbed by the horse, so the absorbed protein = half of 1.3kg = .65kg, or 650mg.

The daily protein range is 1.1 to 2.2 g per kg, so a 650kg horse needs 715g to 1430g daily. The hay and pasture provide less than the minimum amount; it must be remembered that limited forage does not have a complete amino acid profile, so several amino acids will be missing.

1 pound of soybean meal (SBM), or 454g, yields 174g of high-quality protein with all the amino acids (I’ve done the math for this elsewhere). Adding this to the hay ration will yield 650g + 174g = 824g total protein.

Your question is about how much SBM you could maximally feed your 650kg horse daily. To find this, take the maximum amount of total protein allowed (1430g) and subtract the protein from forage (650g), which is 780g. If 454g of SBM yields 174 g of absorbed protein, then 780 / 174 = about 4.5. Therefore, you could feed a maximum of 4.5 x 454g of SBM = about 2kg or 4 pounds daily.

From what I’ve been learning about protein in humans and its effect on building muscle, increasing the quantity of a broad spectrum amino acid profile protein at the maximum amount will trigger muscle development as long as it is fed as a whole food (not a protein shake). Non-meat eaters (vegetarians, horses) may be different. No one knows for sure, but adding exercise to a high quantity of daily protein, especially resistance training, will develop muscle.

Watch his body fat for the summer with the increased sugar in the pasture and new hay. The extra protein may also cause increased body fat if the total sugar consumption exceeds his needs. I hope all this math helps you.

[Kerry]

Thanks again Doc-t. That’s very helpful.