Effect of protein intake during gestation on mammary development of primiparous sows

The effect of protein intake during gestation on mammary development was ev aluated using 17 Landrace x Yorkshire gilts. On d 25 of gestation, gilts we re allocated to dietary treatments consisting of levels of protein to achie ve lysine intakes of approximately 4, 8, or 16 g/d. Diets provided similar amounts of ME (6.5 Mcal/d) and all other nutrients. On d 105 of gestation, gilts were bled through venipuncture to collect blood samples for analyses of blood metabolites (glucose, NEFA, blood urea nitrogen [BUN]), and metabo lic hormones (insulin and IGF-I). Gilts were slaughtered between d 105 and 110 of gestation for complete collection of mammary glands. All mammary gla nds were carefully removed and separated from each other along the midline. One side was weighed, immediately frozen in liquid nitrogen, and stored at -70 degrees C until further processing. Frozen glands were sliced, and par enchymal tissue was separated and pooled across glands within sow, homogeni zed, and analyzed for DNA, RNA, and protein concentrations as indices of ma mmary development. Results showed no effect (P > .10) of level of lysine in take on amount of mammary parenchymal tissue or on concentration or total a mount of DNA, RNA, and protein. This experiment did not detect differences between treatments in mammary development as measured by nucleic acids and protein. Therefore, there was no effect of the amount of protein intake by gilts on mammary development. Regression analyses failed to detect any rela tionships between measures of mammary development and levels of metabolites or metabolic hormones.