As mammals, rats possess mammary glands that produce milk for their offspring. These structures are a component of the female rat’s reproductive system, providing the necessary sustenance for the initial stages of a young rat’s life. The presence and function of these glands are a defining characteristic of the species.
Anatomy of Rat Mammary Glands
Rats typically have twelve mammary glands, arranged in six distinct pairs. These pairs are distributed along the ventral side of the body, extending from the chest area to the groin. Specifically, there is one pair in the cervical (neck) region, two in the thoracic (chest) region, one in the abdominal region, and two in the inguinal (groin) region.
The glands are composed of a branching system of ducts that terminate in secretory structures called alveoli. Each gland has a single lactiferous duct that opens into a nipple, a contrast to species like humans who have multiple ducts per nipple. While both male and female rats are born with mammary tissue, the glands only fully develop and become functional in females. In male rats, the mammary glands remain rudimentary, and they do not develop nipples.
Lactation and Nursing in Rats
The process of lactation, or milk production, is initiated and sustained by hormones. Following birth, the pituitary gland secretes prolactin, which signals the glands to produce milk, and oxytocin, which facilitates its ejection during nursing. The physical stimulation from suckling pups also encourages the continued release of these hormones, ensuring a consistent milk supply.
For the first few weeks of life, rat pups rely entirely on their mother’s milk. The initial secretion is colostrum, a substance rich in nutrients and maternal antibodies. Since newborn rats cannot produce their own antibodies, this colostrum provides them with passive immunity against pathogens. Within a few days, it transitions to mature milk, which supports the rapid growth of the pups until they are weaned.
Mammary Gland Health Concerns
Mammary tumors are a frequent health issue in rats, particularly in unspayed females. These growths appear as soft, movable lumps under the skin anywhere along the mammary tissue, but are commonly found in the armpit, abdomen, and groin areas. While they can occur in younger animals, the incidence is higher in rats over 18 months of age. The development of these tumors is linked to hormones, diet, and genetic predisposition.
The majority of these tumors are benign fibroadenomas, which are encapsulated and do not spread. Malignant tumors, known as adenocarcinomas, are less common but are firmer and more invasive. Even benign tumors can cause serious problems as they grow, sometimes reaching sizes that impede movement, grooming, and eating. Large masses can also become ulcerated, infected, or bleed, leading to anemia.
Due to the high incidence, regular health checks to feel for new lumps are recommended for pet rats. A veterinary consultation is necessary for diagnosis if a mass is detected. Treatment involves surgical removal, and early detection improves the outcome. Spaying female rats at a young age has been shown to reduce the frequency of these tumors.