Factors affecting mammary development in gilts

Abstract

Mammary growth in prepubertal gilts is limited until ∼3 months of age. The rate of mammary tissue and DNA accretion then increases 4–5-fold. In pregnant gilts, there is limited mammary growth in the first and second trimester of gestation, whereas in the third trimester mammary growth is extensive and seems to continue until term. The number of milk-producing cells in the mammary glands of sows at the beginning of lactation is a determinant factor for milk production; yet, little is known about its regulation. Mammogenesis is controlled by a complex interaction of various hormones. During gestation, estrogens are known to be required for mammary development and relaxin is also needed to stimulate total mammary gland growth. A recent study has shown that prolactin is essential for mammogenesis in pregnant gilts. Indeed, inhibition of prolactin with bromocriptine decreased parenchymal tissue weight as well as DNA, RNA and protein contents. Data on the effect of nutrition on mammary development and subsequent milk production are sparse and inconclusive, especially with regard to prepubertal gilts. During gestation, high energy may have detrimental effects on mammary development and subsequent milk production, while the amount of dietary protein has limited effects on mammary development but may increase subsequent milk production. Genetics is also involved in mammogenesis since mammary gland development differs between Upton-Meishan and Large White gilts. This difference may be related to changes in prolactin-regulated genes.