Production of bovine alpha-lactalbumin in the milk of transgenic pigs

High production of milk and its components are necessary to allow maximal g rowth of developing pigs. In this study, transgenic pigs were produced cont aining the alpha-lactalbumin gene, whose product is a potential limiting co mponent in the production of milk. Two lines of transgenic pigs were produc ed to analyze the effects that overproduction of the milk protein alpha-lac talbumin may have on milk production and piglet growth. Transgenic pigs wer e produced through microinjection of the bovine alpha-lactalbumin gene. The gene construct contained 2.0 kb of 5' flanking region, the 2.0 kb coding r egion, and 329 bp of 3' flanking region. Sows hemizygous for the transgene produced as much as .9 g of bovine alpha-lactalbumin per liter of pig milk. The production of the bovine protein caused approximately a 50 % increase in the total alpha-lactalbumin concentration of pig milk throughout a lacta tion. The concentration of bovine alpha-lactalbumin was highest on d 0 and 5 of lactation and decreased as lactation progressed. The ratio of bovine t o porcine alpha-lactalbumin changed during the sow's lactation. This ratio was 4.3 to 1 on d 0 of lactation, but by d 20 of lactation the ratio was .4 3 to 1. This suggested that the bovine transgene and the endogenous porcine gene are under slightly different control mechanisms. The higher level of total alpha-lactalbumin present on d 0 of lactation was correlated with hig her lactose percentage on d 0 in transgenic sows (3.8%), compared with cont rols (2.6%) (P < .01). Although there was also a trend for higher lactose p ercentage in transgenic sows on d 5 and 10 of lactation, no significant dif ferences were observed. These data suggest that alpha-lactalbumin is limiti ng early in lactation of swine. Furthermore, higher concentrations of alpha -lactalbumin early in lactation may boost milk output.