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Eating for heating! How a goat’s rumen works

Eating for heating! How a goat’s rumen works

As the nighttime temperatures remain low throughout much of the country, I have to pause and compare my winter wardrobe to my goats’.  I go all-out for morning chores: insulated coat, thermal underclothes, denim jeans, t-shirt, sweatshirt, long scarf, open-finger gloves and knit hat. My goats meet me at the gate dressed in their fluffiest hair, and…wait… just fluffy hair! And I still have the nerve to complain about the cold!


Goats are able to generate amazing amounts of heat to withstand the cold, due to the amazing design of their digestive system.  They have four stomachs, which is not exactly breaking news. But the process in the rumen, the largest of the stomachs, is fascinating and understanding the process can help us to keep our caprine friends warm all winter.


It is a basic tenet of goat nutrition that they need plenty of roughage – mostly hay in cold weather.  The hay has cell walls made of cellulose, and it’s the fermentation and breakdown of that cellulose that provides the fuel for the goat’s internal furnace.  When hay is put into the manger, the goats eat the hay quickly, but don’t really chew it well enough to turn it into heat.  This is where the amazing adult goat rumen comes into play, since as the goat finishes eating; the real “hot” work begins.


As hay enters the goat’s rumen, it settles in layers.  The bottom layer is the softened hay from yesterday (and the grain from today).  The middle layer is today’s hay, and at the top is gas.  The gas is created by fermentation from tiny microbes that live in the goat’s rumen.  These microbes start anaerobically digesting the cellulose from hay in the bottom and middle layers, which releases gas, plus begins generating heat for the goat to stay warm.


Now, we all know the goat can’t keep the gas, or it will bloat.  Nature handles this with the contractions of the rumen, which causes a bolus of softened hay (cud) to come back up the goat’s esophagus via a burp, and into the mouth for re-chewing.  When the “cud chewing” begins, the gas is also released.  According to a study by Colorado State University, up to 5 liters of gas are released by a goat in an hour of cud chewing!


Once the goat chews the cud and re-swallows it, the microbes continue working on the cellulose again.  These microbes are delicately balanced in the rumen, which is why all feed changes need to be done slowly, so microbe development can keep pace.  Most of the work is actually completed by the microbes, and without them the goat can’t keep warm.  The heat from the rumen’s fermentation can actually be compared to the breakdown in a compost pile and the high heat generated from it!  This is why many goat keepers advocate an endless supply of hay in the winter, since without adequate roughage the goat’s internal furnace will not function correctly.


Once again, this noble creature shows us humans a thing or two about efficiency.  Now if only I could get all the comfort food I eat in the winter to work as an internal furnace!


Meghan Leonard


Meghan Leonard is a veterinary medical technology student, leading to vet school. She lives and learns at her barnyard in southcentral PA, where books and practical goat experience combine.
Disclaimer:  I’m not a veterinarian, and provide advice only based on my experiences.  Please consult a veterinarian with any concerns over your herd.

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