Why can't rats have dairy products? - briefly
Rats produce little lactase, the enzyme required to digest lactose, so dairy intake typically causes gastrointestinal distress and diarrhea. Consequently, dairy foods are unsuitable for their nutrition.
Why can't rats have dairy products? - in detail
Rats produce only minimal lactase, the enzyme required to split lactose into glucose and galactose. In juvenile rodents the enzyme is present, but its activity declines sharply after weaning, leaving adult animals unable to digest the sugar found in milk and cheese.
When lactose remains undigested, it draws water into the intestinal lumen by osmosis. The resulting diarrhea can be severe, accompanied by abdominal cramping, flatulence, and weight loss. The bacterial fermentation of lactose also generates short‑chain fatty acids and gases that exacerbate gastrointestinal distress.
Studies measuring intestinal enzyme levels in laboratory rats consistently report lactase activity at less than 5 % of that observed in humans or in young rodents. Experimental feeding of lactose‑containing diets leads to measurable increases in stool water content and a reduction in feed efficiency, confirming the physiological limitation.
Beyond lactose, dairy products are high in saturated fat and calcium. Rats regulate calcium tightly; excess intake can disrupt bone remodeling and increase the risk of kidney stone formation. The fat profile of cow’s milk differs from the fatty acid composition rats require, potentially contributing to hepatic lipid accumulation and obesity when dairy is offered regularly.
Pet owners should avoid giving milk, cheese, yogurt, or any product with added lactose. If a rodent shows signs of gastrointestinal upset after accidental exposure—watery stools, reduced activity, or a swollen abdomen—immediate removal of the dairy source and provision of fresh water are advised. In cases of persistent symptoms, veterinary assessment is necessary to prevent dehydration and secondary infection.