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Tuesday, February 25, 2020

The Buck Stops Here

By KRISTEN J. DeMORANVILLE/ecoRI News contributor

Downs film animals vintage snow GIFChristian Floyd, a natural-resource scientist at the University of Rhode Island, spotted an unusual white-tailed deer carcass while birding on the South County Bike Path in mid-January.

Floyd went into the woods for a closer look at the carcass. His inspection revealed that this wasn’t a hunting fatality or natural death; the deer’s stomach looked as if it had exploded

The animal’s stomach was enlarged and bursting open with partially digested corn grains. 

The cause of the deer’s death was familiar to Floyd, who recalled a scene from his childhood,” I knew that rumen acidosis was responsible because my favorite goat, Maria, succumbed to the same fate after devouring the chicken feed.”

Ruminants, including deer, goats, and cattle, are a group of animals named after their specialized digestive system that allows them to eat large amounts of nutrient-poor plant material such as grass and woody shrubs. 

In this specialized digestive system, food first enters a chamber called the rumen, which is home to the microbial community — bacteria, protozoa, and fungi — solely responsible for breaking down the large quantities of ingested fibrous plant material.

Shifting away from their normal fibrous diets can disrupt a ruminant’s microbial community and have fatal consequences, a process called rumen acidosis, which occurs when a ruminant suddenly gorges on carbohydrate-heavy meals of corn or other grain. 

In response to this meal, the number of carb-feasting microbes in the rumen dominate the microbial community to cope with the carbohydrate overload. These carb-feasting microbes ferment the ingested corn causing a build-up of lactic acid. The lactic acid lowers the pH of the rumen, causing an acidic environment that destroys the animal’s ability to digest and absorb nutrients.

At this stage, an animal will stop feeding because its gut is too full. However, the animal is functionally starving because of its inability to process the leftover corn present in the rumen. 

At the same time, the excess lactic acid leaks from the rumen into the animal’s bloodstream, damaging cells and tissues throughout the body. Muscle groups are usually too damaged to function, and an animal may be seen staggering or unable to stand.

Rumen acidosis causes the animal’s death within one or two days of its grain-heavy meal.
Dylan Ferreira, a senior wildlife biologist with the Rhode Island Department of Environmental Management’s Division of Fish and Wildlife, noted that rumen acidosis is a concern for Rhode Island’s white-tailed deer population. He said it’s one of the reasons why the state informs people not to feed or bait deer.

Feeding white-tailed deer can be detrimental to entire populations, since feeding can cause large congregations of deer that facilitate the spread of contagious diseases such as chronic wasting disease.

Feeding wildlife can be tempting because it creates seemingly special wildlife viewing opportunities. However, feeding white-tailed deer often harms these animals by disrupting their natural diet and altering their normal behavior.

Kristen J. DeMoranville is a Ph.D. candidate in the Physiological Ecology, Natural Resources Department at the University of Rhode Island.