In lactating or weaned sows, inflammation of a single mammary gland is common. Such uniglandular inflammations are more often noticed in old sows.
The microorganisms involved are the same as those in acute multiglandular mastitis (see Acute Multiglandular Mastitis in Sows). Sometimes only one or two mammary glands are affected; the cause should be identified. Traumatic lesions or inaccessibility of teats to piglets are common. Piglets suckling inguinal mammary glands of old sows are often unable to reach the teat during the phase of milk ejection. Usually, piglets have selected a specific gland by 24 hr after birth. A piglet suckling a teat affected by acute uniglandular mastitis will show growth retardation, while littermates remain healthy. Milk secretion may be restricted by acquired problems of mammary conformation (as in old sows), traumatic lesions, and other teat abnormalities. Teat lesions may have developed during the previous lactation, the previous weaning-to-estrus interval, or the previous gestation.
The integrity of the mammary gland should be checked before each farrowing. Except for cases associated with inaccessible teats, risk factors involved in the development of blind teats should be identified. Traumatic teat lesions can be the consequence of injuries induced by piglets or other sows, or by slipping on slatted floors, etc. Unfortunately, these primary lesions often go unnoticed until several weeks or months have passed. Size homogeneity within a litter should also be monitored. Any discrepancy or growth retardation in a piglet compared with its littermate could be indicative of mastitis in a mammary gland.