California is the land of almonds. In fact, about 80% of all the almonds in the world are grown there, according to Dr. Katherine Swanson, lecturer and researcher in dairy nutrition and management at the California Polytechnic State University in San Luis Obispo, Calif.
On a recent episode of The Dairy Nutrition Blackbelt podcast, Swanson shared the dairy nutrition details of a major almond-based feed commodity: the hulls. Almond hulls are the fleshy outer casing of the almond fruit, and make up about 50-60% of the total weight harvested from almond trees each year.
Those billions of pounds of almond hulls regularly make their way into lactating dairy rations, where they are an excellent source of some nutrients. “Almond hulls are a great fiber source,” declared Swanson. “But they’re not a great substitute for something like alfalfa fiber because they do have a higher lignin content. So they are comparable for NDF, but higher in lignin, so less digestible fiber.”
Where they really shine is in their fermentable sugar content. Swanson said almond hulls are about 60% non-fiber carbohydrates, making them an attractive swap for concentrates in a ration versus fiber.
University of California-Davis Cooperative Extension Specialist Peter Robinson said nutritionists appreciate those soluble sugars, because they ferment readily in the rumen, but do not lead to accumulation of lactic acid.
The one key macronutrient that almond hulls lack is protein, which typically rests at about 3-4%. Still, paired with a protein boost from soy or canola meal at high inclusion rates, they can create a very tidy TMR package that yields both performance and palatability.
Swanson and her colleagues conducted a study commissioned by the Almond Board of California to determine how high the upper bounds of almond hull inclusion could be pushed without affecting production. “Typical inclusion rate is about 2-3 pounds per cow per day,” shared Swanson. “In our study, we fed them at about 20% of the diet, or about 12 pounds per cow per day, which didn’t really have a lot of negative effects except for milk protein.”
Like many co-product feedstuffs, almond hulls are most economically advantageous to dairies that have nearby access to minimize freight costs. Robinson said dry almond hulls are usually delivered to dairies between 88 and 91% dry matter. They are only mildly hygroscopic, meaning they absorb little water. In a TMR of 40-50% moisture, they will only gain 2-4% in weight. But that small amount of moisture absorption makes them highly pliable and easy for cows to consume, with little sorting.
Swanson cautioned that their porous nature does make almond hulls susceptible to mold growth if not stored properly. And because they are a fairly low-density product, shipping them long distances does not typically pencil out, although some product is now being trucked to Texas.
“The Almond Board is interested in finding ways to get more almond hulls out of California, because we’re not physically able to feed all of them,” shared Swanson. Two options under exploration to make almond hulls more export-friendly are creating a pelleted product, and cubing them in combination with lower-quality alfalfa.
“They are definitely valuable feed,” Swanson stated. “I think about a 10-15% inclusion rate is reasonable, and may actually help improve milk fat percentage, which can help offset a little bit of dip in milk protein.”
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