Les malabars sont au parfum(1966)

All sorts of spies are buzzing around Michel, whose cow, Dorothée, produces 200 liters of milk a day thanks to a treatment of his own invention. Dorothée is kidnapped and found. But now everyone disowns her. No matter! Dorothée's productivity will enrich Michel and his wife Nicole, who have opened a rotisserie; milk cocktails are in fashion.