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COUNTRY LIFE IN BC • JANUARY 2020


Clay improves degradability of dairy feed A small amount of dirt goes a long way towards herd health, productivity


Considerable research has been done on clay supplements fed to dairy cows and past research has shown how they not only improve milk quality but help the cow’s immune system and reduce the symptoms of aflatoxin in lactating cows.


Research by MARGARET EVANS


Now, a new study from the


University of Illinois has shown that clay can also improve the degradability of feedstuffs. “There were some differences in


how the feedstuffs degraded over time,” said Phil Cardoso, associate professor in the Department of Animal Sciences. “When clay was added to grass hay at 2% of dietary dry matter, the digestibility and usage of the fat in that material was maximized. It's better. And we didn't see a decline in degradability of the other feedstuffs, either. Overall, to maximize the benefits of clay, we'd recommend adding it at 1% to 2% of dietary dry matter.” Cardoso said that while dairy farmers recognize the benefits of clay supplements, they often wonder


if the corn silage or hay the cow is eating is affected. The study found that the clay changes the way the cow degrades the feed. Cardoso’s team tested the


degradability of six feedstuffs – dried alfalfa hay, grass hay, wet brewer’s grains, ground corn, corn silage and soybean meal. They were tested at different exposures. One test was with no added clay, and other tests were clay additives at 1% or 2% of dietary dry matter. The feedstuffs were


placed into mesh bags and inserted directly into the rumen through a cannula, which is a thin tube inserted into a vein or body cavity for the purpose of delivering medication or removing organic samples. In this case, the cannula was a surgically installed portal allowing the contents of the rumen to be sampled. The mesh bags were drawn out at various times – anywhere from two hours to four days – and analyzed.


Some differences “There were some differences in


how the feedstuffs degraded over time,” said Cardoso. “When clay was added to grass hay at 2% of dietary dry matter, the digestibility and usage of the fat in that material was maximized. It’s better. And we didn’t


see a decline in degradability of the other feedstuffs, either. Overall, to maximize the benefits of clay, we’d recommend adding it at 1% to 2% of dietary dry matter.” Past studies led by Cardoso


showed that multiple types of clay effectively handled aflatoxins which are toxic metabolites produced by fungal contaminants in feed. Biological effects can affect the liver, kidneys and central nervous system. Many alfatoxins are known but only some fungi produce them. When the toxin is bound up by the clay, it is simply excreted from the cow’s body rather than being absorbed in the bloodstream. In a 2018 study, Cardoso’s team


showed the aluminosilicate clay not only improved a cow’s immune function but also reduced liver inflammation during an aflatoxin challenge. “From all our work on this, I can


tell producers that, whenever they are facing the risk of aflatoxin, they should consider using clay without worrying about it binding other minerals or hindering forage digestibility,” he said. “Rather, we've shown digestibility could increase. Of course, it's important to ensure the specific clay product has been tested.”


The 2018 study also revealed a that a gene involved with protein


production, known as MTOR, was negatively impacted by aflatoxin. But, with the addition of clay to the diet, there should be a decrease in aflatoxin reaching the milk in addition to a potential boost in the immune system. Cardoso said that clay benefits do not stop there. Because the material attracts and binds positively charged ions, clay can make the rumen less acidic. This is important, he said, particularly given the popularity of increasing grain concentrates in total mixed ration (TMR) feed, which can lead to subacute ruminal acidosis (SARA) in lactating cows.


Clay has benefits In a 2016 study from Cardoso's


group, cows challenged with excess wheat in a TMR diet produced more and higher-quality milk and had higher rumen pH when fed bentonite clay at 2% of dietary dry matter.


“Basically, clay has all these


benefits,” said Cardoso. “It reduces aflatoxin toxicity, works as a pH buffer, and improves the degradability of some feedstuffs.” The study was published recently in the journal Animal Feed Science and Technology. Margaret Evans is a freelance writer based in Chilliwack specializing in agricultural science.


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