Transgenic Over-Expression of Bovine α-Lactalbumin and Human Insulin-Like Growth Factor-I in Porcine Mammary Gland

Abstract

The first week postpartum is the period of greatest loss for US swine producers, with most morbidity and mortality attributed to malnutrition and scours. Despite the benefit to be gained by improving lactation performance, little progress has been made in this area through conventional means. Transgenic technology provides an important tool for addressing the problem of low milk production and its detrimental impact on swine production. Transgenic swine over-expressing bovine α-lactalbumin (α-LA) and human IGF-I were developed. α-Lactalbumin was selected for its role in lactose synthesis and regulating milk volume. IGF-I regulates mammary development and piglet intestinal development. The IGF-I construct consisted of the IGF-I gene inserted directly behind the α-LA signal peptide coding sequence to allow secretion of IGF-I into milk. Outcomes assessed were milk composition and yield and piglet growth and intestinal development. First parity α-LA gilts (n=8) had higher milk lactose content in early lactation and 20 to 50% greater milk yield on d 3, 6, and 9 of lactation than nontransgenic gilts (n=10). Weight gain of piglets suckling α-LA gilts was greater from d 7 and 21 postpartum than control piglets. Colostral IGF-I was ∼10-fold higher in first-parity IGF-I transgenic gilts (n=5) than non-transgenic gilts (n=4), and elevated milk IGF-I is maintained throughout lactation at ∼0.6mg/L. Milk yield tended to be greater in IGF-I transgenic swine in early lactation. Thus, transgenic over-expression of milk proteins and growth factors may provide a means to improve swine lactation performance.