Holy Cow! Does your milk come from cows that have a plastic sniffing habit?

Much has been written about the plastic cows of India and the deadly effects plastic has on cows that ingest them. Cows that eat plastic are found to eventually stop eating regular food. Plastic invades their internal organs. Toxic chemicals like dioxins have been found in their milk. Cows are known for their very sensitive sense of smell. Even their memory, communications and tracking of their calves are found to be associated with their keen sense of smell. Cows also have a special appendage in the roof their mouths called the ‘Jacobson’s organ’ which doubles as an olfactory organ – a smell detector, if you will. We often see cows looking up or curling their lips with an open mouth. This seemingly-awkward behavior are visible signs of a cow using the Jacobson’s organ in response to an unfamiliar smell. Cows accept or reject food based on smells and seek food based on smell as well. [caption id=“attachment_5842631” align=“alignnone” width=“1280”] A cow on a plastic binge.[/caption] Could the attraction of cows in India to plastic be related to their prodigious olfactory ability? If we were to hypothesize based on the impact of plastic’s smell on other species, it would seem so. A European study recently reported that nearly 10 types of plastics were found in human stool. This is not surprising considering that plastic has been found in water, beer, and seafood. Oceans cover seventy percent of Earth’s surface area and are the largest shared resource for humans. Plastic pollution of oceans is now very widespread. Plastic is found not only predators like fish, sea turtles and seabirds but also in seafloor sediments. An award-winning essay in journal Science by Matthew Savoca of Stanford University reported that the attraction to plastic by some species may be entirely related to the odor being emitted by the plastic. This finding could explain why some species avoid plastic but some seem to never get enough of it. This would also imply that it may not be the visual cue that may matter; for example, sea turtles eating plastic because it resembles jellyfish which is turtle’s natural food. [caption id=“attachment_5842641” align=“alignnone” width=“1280”] Green sea turtle with plastic bag in the Great Barrier Reef. Image courtesy: WWF Australia[/caption] The sense of smell that gets triggered in marine species is related to a chemical called dimethyl sulfide or DMS and its derivatives. Algae or phytoplankton are the bottom of the food chain in water just as plants and grasses are on land. Algae photosynthesize and produce the carbohydrates needed to support the entire food web in a waterbody. Herbivores like zooplankton consume phytoplankton and the partially consumed phytoplankton tends to get consumed by bacteria to produce DMS. DMS has a distinct odor. Where there is DMS, there are zooplankton and zooplankton like krill are consumed by fish and fish are consumed by other predators like sea turtles and seabirds. Marine species thus track DMS to find food. Savoca’s experiments with polypropylene and polyethylene, the pre-products used in making most of the plastics, showed that plastics in water get rapidly covered by a layer of algae. This is, in fact, true for anything that is placed in water. For example, the instruments put in the water to measure currents, temperatures, etc., get covered with algae and can become inoperative unless protection is provided against this biofouling. It is the algae cover on plastics that produces DMS and is the culprit in attracting marine species. [caption id=“attachment_5842651” align=“alignnone” width=“1280”] A young turtle eating plastic. Image courtesy: Queensland Department of Education[/caption] Ocean-weathered plastic was found to emit a thousand times more DMS than in a natural environment. Clean plastic was found to have no DMS signature. While Savoca’s study only focused on marine species, is it possible to hypothesize that millions of cows in India are routinely seen feasting on plastic because of the same ‘olfactory trap’? The warm climate in India may be playing a part in degrading plastic to produce certain odors. Continued use of plastic in packaging food products and garbage piles of food products mixed with plastic may also be contributing to misleading the bovines. It is an urgent imperative that research is done on the odors associated with plastics in India, and a map of specific odors that cows find savoury. Potential solutions may emerge from such a study, for example, neutralizing specific chemicals in plastics may make them unattractive to cows. Cows are consuming plastic to their own severe detriment as well as to that of consumers of dairy products. Many valiant efforts are underway to ban plastic across India but most garbage piles and trash strewn around still contain unacceptable amounts of plastics. The campaign names Swaccha Bharat or Clean India will certainly be very healthy for the Holy Cow as well as humans who depend on them for milk and other products.