03rd May 2008

Myth – Rats cannot digest alfalfa

How often have you heard from a friend or read on someone’s blog that alfalfa is not digestible by rats and other nonruminant omnivorous rodents? This notion pops up quite often in the pet blogosphere. So, to put the myth to rest, I summarize, below, some of the well-established facts about the nutritional value of alfalfa grass for animals, particularly omnivore rodents, in the hopes rehabilitating the reputation of this venerable and valuable herb.

Historically, alfalfa is one of the earliest cultivated plants; the name is actually derived from the Arabic word “al-fac-facah,” which means “father of all foods.” The scientific term for alfalfa is “Medicago sativa.” It is a perennial legume that grows in the foothills and mountains of North America, the Mediterranean region, and Western Asia. For a variety of reasons, alfalfa is one of the most nutritious foods known. The whole plant contains many important nutrients, including saponins, sterols, carotene, phytoestrogens (e.g., coumestrol), flavonoids, alkaloids, acids, vitamins (including A, B-6, D, E, K, and U), amino acids, sugars, proteins, minerals (e.g., calcium, chlorine, copper, magnesium, iron, phosphorus, potassium, sodium, and sulphur), as well as trace elements. The abundance of these nutrients, as well as chlorophyll and vital digestive enzymes, makes alfalfa an important nutritional supplement. The plant has antihemolytic, antitumoral, and antibiotic properties. In traditional medical practices across cultures, it is used to alleviate arthritis, as a tonic, an appetizer, and a diuretic to relieve urinary and bowel problems.

The oft-floated argument that alfalfa is not digestible by rats and other nonruminants is often combined with the false statement that alfalfa is the equivalent, in both composition and nutritional value, of cellulose. This is simply wrong. Alfalfa is much more than indigestible fiber, which, by the way, is itself important for good health. Alfalfa contains a high amount of digestible protein and fiber, numerous essential minerals, amino acids, and vitamins, and is used in many rodent diets as a source of both protein and fiber (e.g., in many of Harlan Teklad’s rodent diets). What follows should explain why this is the case.

Alfalfa contains about 26% protein and 24% fiber (1). These percentages vary with season in which the plant is harvested, as well as by different parts of the plant used; accordingly, in stem and leaf, protein and fiber percentages range from 16-36% and 12-35%, respectively.

A number of controlled nutritional studies have used rats and other omnivore rodents as models; these have shown that alfalfa is a beneficial food for these animals. Below, I summarize some of these studies to reinforce the point that alfalfa is not only digestible, but also very supportive of omnivorous rodent health (I don’t include studies done with herbivore rodents, in which alfalfa showed similar health benefits).

Fiber, cellulose fractions, and protein in alfalfa hay were found to be relatively well digestible by rats (2). Fiber was digested by rats with an average digestion coefficient of 20%, which is approximately 50% less than the coefficient established in sheep (45%). However, the hemicellulose contained in the alfalfa was digested with an average digestion coefficient of 47%, which is precisely that found in sheep (47%). Cellulose was digested by rats with a coefficient of 21% (compared to 50% in sheep), and crude protein was digested at a coefficient of 52% as compared to 69% in sheep. So, as nonruminants go, rats don’t do too badly in digesting this legume.

Alfalfa and alfalfa fiber fractions (3), as well as alfalfa protein (4) are digested by rats and tend to support animal growth. In fact, rats digest protein contained in alfalfa more efficiently than that found in roasted nuts or corn (5).

In isolation from alfalfa fiber, saponins in alfalfa meal reduce cholesterol absorption (6, 7). The ability of alfalfa to reduce liver cholesterol accumulation was enhanced by removal of cholesterol by saponins. In this study, an interaction of alfalfa components with bile acid was suggested as a possible mechanism for alfalfa’s saponin-independent hypocholesteronic effects (8).

Alfalfa also reduced radioactive cesium absorption and retention in both gut and other organs examined in suckling rats (9). In addition, alfalfa was shown to decrease the body’s burden of several other heavy metals (cadmium, strontium and mercury)

Dietary alfalfa reduces mycotoxin toxicity, manifested in rats in such conditions as retarded growth and food refusal (11, 12, 13).

Dietary alfalfa leaf meal (powder) counteracts growth retardation, “unthrifty appearance” of the fur, and a 50% increase in death rate associated with so-called purified diets containing levels of 5% of the food colors tartrazine (FD&C Yellow No. 5) and sunset yellow FCF (FD&C Yellow No.6) (14). Many pet food manufacturers use these food coloring agents to make their products appear more attractive to the human eye. Although one would hope that food manufacturers would use significantly less than 5% of these substances, chronic use of these colored foods might well lead to health problems similar to those described in this particular study.

Dietary alfalfa meal counteracts the toxic effects (severe diarrhea, “unthrifty appearance”, alopecia, and decreased survival rates) caused by non-ionic surfactants in immature rats. Wheat grass and other grass powders were also effective in the same study. These protective effects were only partially due to the cellulose contained in alfalfa, and were not observed when dried alfalfa grass juice was fed to the subject animals. (15). The same beneficial effects of alfalfa feeding were found in a study involving immature mice (16).

Dietary alfalfa meal prolonged the survival of hyperthyroid rats (17) and protected rodents (rats and mice) from mineral oil-induced toxicity (18). This particular study is of great interest because other petroleum-based substances used in the manufacture of pet foods may well have negative effects similar to those of mineral oil. Although propylene glycol is not considered to be safe for use in any foods, whether human-grade or otherwise (e.g., for cats), some pet food manufacturers use this oil in their formulations for “pocket pets,” particularly rodents.

Alfalfa powder improved growth and survival rates of hamsters on highly purified diets (i.e., diets composed of isolated nutrients, not “natural” diets) (19).

It has been found that dehydrated alfalfa is more nutritive and contains more vitamins, minerals, and amino acids than sun-cured alfalfa. It was shown that lower drying temperatures increased the digestibility and bioavailabilty of the protein for rats (20). This is of particular interest if one considers that most foods are produced using high heat (e.g., heat extrusion for creating pellets, attractive shapes, or high temperature baking). Always remember Onesta Organics products are created without using high heat, so the nutrients in alfalfa and the other ingredients we use remain intact.

I hope that my blog about alfalfa will help rehabilitate its reputation in your eyes. More importantly, though, I hope I have effectively demonstrated the great value of this under-appreciated herb for your pet rodent’s nutrition. Thanks so much for reading! To you and your pet: good nutrition, good health, and a great life!

1. Popovic et al, CIHEAM Resources
2. Keys et al. J Anim Sci 1969, 29/1, 11
3. Meyer, J Nutr 1954, 54/2, 237
4. Cheeke et al., J Anim Sci 1977, 44/5, 772
5. Takyi et al., J Sci Food Agricult 2006, 59/1, 109
6. Malinow et al., Am J Clin Nutr 1977, 30/12, 2061
7. Malinow et al., Am J Clin Nutr 1979, 32/9, 1810
8. Story et al., Am J Clin Nutr 1984, 38/6, 917
9. Kargacin et al., Arch Toxicol 1987, 59/5, 371
10. Kostial et al., Toxicol Lett 1984, 23/2, 163
11. Smith, Can J Physiol Pharmacol 1980, 58/11, 1251
12. Carson and Smith, J Nutr 1983, 113/2 304
13. Smith and Carson, Adv Exp Med Biol 1984, 177, 153
14. Ershoff, J Nutr 1977, 107/5, 822
15. Ershoff, J Nutr 1960, 70, 484
16. Ershoff and Hernandez, J Nutr 1959, 6, 172
17. Ershoff et al., J Nutr 1950, 67/3, 381
18. Ershoff and Hernandez, J Nutr 1958, 65/4, 575
19. Ershoff, J Nutr 1956, 59/4, 579
20. Cheeke et al., J Anim Sci 1977, 44/5, 772

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One Response to “Myth – Rats cannot digest alfalfa”

  1. Premium Pet Foods: What Should I Feed My Rat Says:

    [...] Yes, alfalfa fiber is indigestible by rats, but the rest of the plant is benefittingly nutrious. You can read a summary with references at Nesta Organic’s post on the topic. [...]