#Text and pictures: Pari Baker

Dairy heifers are a sizable financial investment for producers and therefore should enter first lactation healthy in order to yield good return on investment. Most mammary growth and development occur during a dairy heifer’s first gestation and this initial development determines the number of secretory mammary epithelial cells in the lactating gland. The heifer mammary gland prior to first gestation is primarily composed of the mammary fat pad and contains minimal mammary epithelium. With the initiation of pregnancy, this previously existing mammary fat pad is replaced by secretory mammary epithelium. Unfortunately, coupled at this time is the increased prevalence of intramammary infections (IMI) as a result of pathogenic bacteria entering the mammary gland via the teat canal and establishing an infection. Such IMI are expected to shortchange future mammary maturation and ultimately reduce the number and/or functional capacity of secretory mammary epithelial cells. However, how these IMI affect mammary gland growth and development in rapidly growing and developing mammary glands has not been investigated. Therefore, Dr. Pari Baker explored the effects of intramammary infections on mammary gland growth and development in nulligravid heifers.