Contrary to popular belief, the majority of dogs who graze on grass do not try to make themselves vomit: behavioral studies show that less than a quarter of episodes of grass ingestion are followed by vomiting, and that this behavior is not systematically preceded by signs of digestive discomfort.
Behavior with multiple origins
The dog descends from an opportunistic ancestor whose diet already included plants consumed directly or via the stomach contents of herbivorous prey. Grazing on grass could therefore be part of a preserved ancestral dietary behavior, independent of any purgative intention. Taste and texture also come into play: some dogs simply seem to enjoy chewing on fresh sprigs, especially in spring when the growth is tender.
The fiber hypothesis is also documented: grass provides indigestible cellulose which can stimulate intestinal transit, a bit like a dietary fiber supplement. Finally, exploratory behavior and boredom play a significant role: a dog that sniffs, chews and grazes during a walk uses its sense of smell and occupies its time, which explains why this behavior is more common in dogs with little mental stimulation or left alone in the garden for a long time.
When to worry?
This behavior is therefore most often benign and does not reflect either deficiency or illness. On the other hand, it becomes a warning signal if it is accompanied by repeated vomiting, lethargy, a sudden change in appetite or if it is associated with the ingestion of large quantities of treated grass (pesticides, fertilizers). In these cases, a veterinary consultation is recommended to rule out an underlying digestive disorder.
