Picture is of Shangri-La the day I harvested it. The size is hard to tell from this picture, but they are large, plump fruits.
Who ever thought mulberry fruits could have 18% protein?
In a previous article I laid out the case for the strong nutritional profile of mulberries, both the leaves and especially the fruit. Leaves have long been valued and studied for their high protein content and digestibility, but fruit has received much less attention, despite it being incredibly important for pastured pig and poultry farms in the pre-WWII South. One suspects that if big companies stood to make big money from mulberries rather than corn, we would know everything there is to know about mulberry fruit by now.
Because I wasn’t completely confident in the snippets of information I was able to piece together from online sources, I decided to conduct my own testing. Once June rolled around, I collected samples from two mulberry cultivars (Shangri-La and Oscar) and one goumi shrub and submitted those to a lab to test for protein, amino acids, and fats. The raw results are available here.
I’ve transposed all the data so the units would line up with the data in the last article allowing us to compare the feed values of mulberry leaves and corn and to compare those values to the protein requirements of pigs at various growth stages.
% Protein of mulberry fruits, mulberry leaves, and corn | % Protein requirements for various pig stages | ||||||
Shangri-La Fruit | Oscar Fruit | Mulberry Leaves | Corn | Early finisher | Late Finisher | Gestating Sow | |
Lysine | 0.36 | 0.29 | 1.23 | 0.29 | 0.73 | 0.57 | 0.51 |
Methionine | 0.26 | 0.14 | 0.30 | 0.19 | 0.20 | 0.16 | 0.14 |
Threonine | 0.35 | 0.25 | 1.05 | 0.33 | 0.48 | 0.38 | 0.51 |
Tryptophan | 0.10 | 0.10 | 0.74 | 0.07 | 0.13 | 0.11 | 0.10 |
Crude Protein | 17.92% | 11.90% | 20.4 | 9.3 | 17.20 | 14.7 | 13.78 |
A couple takeaways:
- These tests confirm that the protein content of mulberry fruit is indeed quite high, higher than most other fruits. 12% and 18% protein is remarkably high for a fruit. In comparison, apples have 5% protein as percentage of dry matter and American persimmons just 2.5%.
- The amino acid profile of the fruits is lower than expected given the much higher crude protein content (2-3x) of the fruits I tested compared to those in the first article (which was based on online research).
- That said, the amino acid values are still on par with corn, and crude protein for Shangri-La fruit is double that of corn.
- Where mulberry fruits are below the amino acid nutritional requirement for pigs is in lysine and threonine, both of which are high in mulberry leaves. Thus the tree is uniquely suited to offer a complete ration.
- There is a significant difference between these two cultivars in terms of protein, fats, and amino acids. Which makes me wonder:
- What other attributes will we find once we can test more of these fruits?
- Will we find cultivars bearing fruit with over 20% protein or with significantly higher content of certain amino acids?
- Also, what factors are at play other than just the cultivar of the tree? Pollination comes to mind, as these fruits were in blocks of mostly grafted trees likely with few males around. Maybe having some male trees around would increase the number of seeds and hence amino acid content. The impact of soil health on fruit quality comes to mind as a factor to investigate as well as how long a growing season the tree experiences. (There’s a lot to learn and study, but these are intriguing findings so far and open up a ton of new research possibilities. If someone is looking for a grad project, this needs more research!)
Note that Shangri-La fruits were selected for testing because they are very large, easy to collect, and yielded very heavily. I can’t say the flavor was great from a human perspective, somewhat bland, but the nutritional profile turned out to be very strong.
Oscar also yielded heavily and the flavor was much stronger, more appealing than Shangri-La yet the fruits are only ⅓ the size. Fruit size should be a factor when choosing mulberry cultivars as livestock will have to work harder to find smaller fruits. I doubt that would be any issue for poultry, but it could be a factor for pigs. And if cattle or sheep are to use mulberries, you’ll want the largest fruit you can get, especially for cattle.