Nitrates from livestock urine can contaminate groundwater, potentially threatening human health. What’s more, nitrous oxide that arises when livestock urine and faeces mix can cause respiratory problems and contribute to global warming.
By training cattle to void directly into a sort of “cow toilet”, however, Lindsay Matthews at the University of Auckland in New Zealand and his colleagues have potentially found a way to keep water and air cleaner, improving health and welfare for both humans and animals.
Matthews’s team taught 16 5-month-old Holstein heifers to use a custom-built, plastic-grass-floored latrine when they felt the need to urinate, using a three-step training process. First, the team placed pairs of calves in the latrine until they urinated; then gave them a treat – either diluted molasses or barley – through an automatic dispenser and opened the exit door.
Next, the team placed the calves in a 2-metre-long alley next to the latrine, which had a gate that the animals could push open in order to enter the latrine. When the heifers urinated inside the latrine, they received the tasty treat, but if a calf urinated in the alley, the team activated a water sprinkler that sprayed it for 3 seconds – an experience thought to be unpleasant for the animals. In the final step, the team opened up the alleyway to form a wider enclosed space for the cows to move around within. The calves continued to either get a either reward or a spraying depending on whether or not they urinated in the latrine.
Unlike humans and many other animals, cows don’t naturally make efforts to restrict waste to a particular place or to hold their bladders, says Matthews. Even so, within 10 training sessions, 11 of the heifers were using the latrine 77 per cent of the time. Their performance topped that of human toddlers learning to toilet train, he says.
“It was fascinating how fast they learned,” he says. “The average was 20 urinations from beginning to end. It was unbelievable.”
Nitrous oxide is much less abundant than other greenhouse gases, but it is 300 times more potent than carbon dioxide and 10 times more so than methane, says Matthews. Inside barns, stagnant urine can damage cows’ hooves, and the gases can cause respiratory disease in animals and humans.
Matthews says he hopes an automated training system can be developed so that cattle farmers throughout the world can benefit from the latrine system. “If we could find a cost-effective way to do it, we could have a pasture with mobile toilets,” he says.
Journal reference: Current Biology, DOI: 10.1016/j.cub.2021.07.011
Sign up to Wild Wild Life, a free monthly newsletter celebrating the diversity and science of animals, plants and Earth’s other weird and wonderful inhabitants