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Quality Protein of SBM vs alfalfa
I wanted to share this article on quality protein from The Horse and ask a question I’ve been meaning to ask here for a while.
Link to article:
Quote that promoted my post:
“Consider forage when choosing high-quality protein sources for your horse, says Carey Williams, MS, PhD, professor in the Department of Animal Sciences at Rutgers University, in New Brunswick, New Jersey. Alfalfa and other legume sources of protein are favorable, followed by soybean meal if a horse needs more protein beyond what forage can provide, she adds.”
I’ve been wondering how much alfalfa would a horse need in its diet to meet its protein requirements without adding soybean meal? Alfalfa has all the amino acids, just not in the same concentration as SBM, and not as bioavailable. Looking at the chart in this article (https://blueseal.com/nutrition-note/soybean-meal-and-protein-in-the-horse-diet/) I found that SBM provides 2.96 lysine while alfalfa provides only 0.74. I also read that SBM has a low calcium profile that niftily balances out the high calcium in alfalfa, making the combo of them in my horses’ diet a great combination.
But for folks with horses with soy sensitivity, can protein needs be met by alfalfa in the diet without soy? How many pounds of alfalfa a day would that mean? Would it require supplementing with specific amino acids (individual amino acids lysine, methionine, and threonine) and can that be done? Would you be able to sufficiently balance the high calcium of alfalfa in the diet with only grass hay/pasture?
I was astounded to see the second article state: “In a study conducted at Texas A&M University on soybean meal digestibility, true total tract digestion of soybean meal protein was found to be 95.3%.” I had understood it to be more like 80%. If this is correct, then SBM is even more awesome than I’d thought, nearly twice as much as alfalfa’s 50% bioavailability.
I look forward to your thoughts Dr. Tucker. There are enough soy avoidant folks that have asked me about The Diet that I wanted to have a better understanding of alfalfa’s dietary benefits/limitations for answering questions.
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4 Replies
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Oh Goodness! @Kathy – Where do I start?
1st, I think my message is getting out because these articles show discussions about protein. But regarding the quality of this information, I would never trust what they say. Anything written by a grain/feed company (Blue Seal) is biased. I need to see the Texas A&M study, but I must get to work right now. I will be looking for the materials and methods used and how they compare with what has been used in the past. Is this a real difference, or is it a technical difference, meaning that we have been feeding the same bioavailability all along and not that it has increased with new processing procedures?
The Rutgers nutritionist needs to check her facts. I receive their newsletter and am constantly amazed that people in NJ spend money to learn there. I know this sounds harsh, but:
This is wrong – “Most horses only need about 8-10% crude protein in the diet,” says Williams.
This is wrong – “As long as a horse has healthy kidneys, they will excrete the excess protein as urea and ammonia; however, I would be concerned with older horses, as prolonged excess protein in the diet can become hard on the kidneys,” says Williams. Quality protein sources are often expensive, so excess protein in the diet means you’re wasting money, she adds.
This is misleading – In her recent study Loos notes that about 0.25 grams CP/kilograms body weight (~ 140 grams CP for the average 550-kilogram/1,200-pound horse) of a high-quality source was sufficient to result in near maximal activation of the muscle synthetic pathways. “Feeding more than this amount provided no additional stimulation,” she says. “Practically, these studies illustrate that we don’t necessarily need to feed a lot of protein to provide maximal stimulus to the muscle—more important is the quality (of the protein) we feed.”
Her take-home message starts off accurately, then fizzles off with inaccurate statements – When selecting protein sources for horses, it is crucial to consider high-quality sources that are easily digestible with good amino acid profiles. It’s also important to evaluate the protein content of feed sources, especially hay, to determine if your horse needs additional protein supplementation. Avoid oversupplying protein, as it can lead to several issues and increase your feed expense.
Finally, her bio reveals her bias (especially the last sentence): Madeline Boast completed her master’s in Equine Nutrition at the University of Guelph and started an independent nutrition company known as Balanced Bay. She has worked with a variety of equids—from Miniature Ponies to competing Thoroughbreds. Boast designs customized balanced nutrition plans that prioritize equine well-being, both for optimal performance and solving complex nutritional issues and everything between.
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Thanks for rebutting the facts. When you have time I hope you can get to the alfalfa part of my Q after finding that Texas A&M study.
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@Kathy Here is a link to Standlee’s nutritional analysis of forage:
They state the crude protein of alfalfa is 16%. With a bioavailability of 50%, the actual protein content becomes 8%.
If fed an all-alfalfa diet of 1.5% to 2% body weight, the total hay for a 1200-pound horse would be from 18 to 24 pounds. For simplicity, let’s take the median value of 21 pounds.
21 times 8% = 1.68 pounds. Converting this to grams (x 454) = 763g
The protein intake goal is 0.5g to 1.0g per pound of body weight. Therefore a 1200-pound horse should eat between 600 and 1200 grams of protein daily. Eating 21 pounds of alfalfa meets this range. However, would this be enough for the horse?
In human longevity medicine, where health span is the goal, most practitioners suggest a variety of unprocessed foods to meet the highest goal of microbiome health. To achieve this in horses, they all need to return to migrating across the land to obtain a wide variety of plants. In reality, most horses eat a limited number of plants between a seeded pasture and only a few hay varieties; further, the amino acid profiles of this limited number of plants probably miss the limiting amino acids (lysine, threonine, methionine).
One of the best solutions is to provide a source with a different amino acid profile of ground plants. This is achieved with soybean meal; however, you could also use a man-made source such as a try-amino mix. The skeptic in me questions the quality and the quantity of man-made sources. Who made the AAs? How long ago were they made, and how were they stored? Is the product profile in the container the same as what is printed on the label?
Now, let’s look at the cost. A quick look at alfalfa prices shows a range of $5 per 40-pound bale if bought by the ton to $12 to $18 per 55-pound bale. It is higher than this in South Florida. Assuming the $12 per 50-pound bale (I am averaging here), 21 pounds would cost about $5. Soybean meal here in South Florida costs about $25 per 50-pound bag. Feeding 1 pound daily, which provides 174 grams of high-quality protein, would cost $0.50.
Soybeans and alfalfa are legumes. Other legumes include beans, chickpeas, peanuts, lentils, lupins, mesquite, carob, tamarind, and clover. Horses and legumes get along due to their microbiome and digestive process, but humans may or may not do well with legumes. The seeds of legumes have high-quality protein with an AA profile guaranteed by nature.
But I want to examine the elephant in the room, glyphosate (Roundup) and genetic modification. Here is a link to a web page discussing the merits of “Roundup Ready Alfalfa.” https://www.americasalfalfa.com/Alfalfa-Varieties/Roundup-Ready-sup-®-sup Worrying about a genetic modification should be extended to alfalfa and, in fact, all hays, including grasses. Look at the ingredients of the grain mixes you feed your horses from any brand and mix configuration (senior, grow, etc.). Most have soybean meal, alfalfa meal, or both. I’ll bet they are Roundup-ready varieties. Added to this are the byproducts of the grain industry; throw-away items that become profitable when sold to unsuspecting horse owners.
This has become a long-winded answer to your question, “I’ve been wondering how much alfalfa would a horse need in its diet to meet its protein requirements without adding soybean meal?” I did not address the calcium issue as I do not believe high calcium (to a point) causes a problem in horses. This is based on horses fed ration balancers, which all have monocalcium phosphate, dicalcium phosphate, and calcium carbonate added to prevent rickets, have no grains but only byproducts, SBM, and alfalfa (and the vitamins, minerals, and yeasts). Additionally, there are many farms where alfalfa is inexpensive, feeding it exclusively without issues from calcium. Finally, while bones are a calcium reservoir, so are muscles, which increase in density with the added branch chain AAs (leucine, isoleucine, valine) of SBM and are lower in alfalfa.
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Very helpful, thank you!
(And I’m paying, gasp, $25 for a 55# bale of western alfalfa. Insane. But the quality is very good.)
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