Cannulated cow

[7] By analyzing the chemical composition of a cow's rumen, researchers can determine the effects of different feeds and processes on bovine digestion.

For instance, a 1939 study discovered via cannulated cows that the pH of rumen varies throughout the day, becoming most alkaline just prior to feeding.

Instead, rumen liquor is aspirated through a rumen-fluid collector, consisting of a Frick gag and a flexible hose with a perforated metal tip which serves as a filter.

[10] Though veterinarians and bovine farmers point to the effectiveness of transfaunation for treating digestive disease, many animal rights groups argue that the practice is unnecessarily harmful to the quality of life of the cannulated cow.

People for the Ethical Treatment of Animals points to the surgery's four- to six-week recovery period and suggests that arguments for the health benefits of cannulation obscure the profit motive of the dairy industry: "While some claim that this transfer can improve the health of cows, the procedure seems mostly to benefit the meat and dairy industries' bottom lines—optimizing food and digestion for animals who will ultimately be exploited and slaughtered.

"[11] Similarly, The New Zealand Anti-Vivisection Society describes the practice as "cruel, insensitive and barbaric [...] the epitome of using cows as mere objects, like cars with gas tanks.

For instance, a 1940 study used cannulated cows to determine that a vitamin-rich diet makes for more antiscorbutic milk than a vitamin-poor diet,[14] and a 2004 study used cannulated cows to evaluate treatments for a pH imbalance called subacute ruminal acidosis that is of concern to dairy farmers primarily because it damages milk production.