Relations between standardized ileal digestible lysine (protein) intake in late-gestating primiparous sows, mRNA abundance of candidate genes in mammary tissue, and subsequent milk yield and composition

Twenty-nine late-gestating primiparous sows were used to assess the relationship between mRNA abundance of select genes in mammary parenchymal tissue under differing standardized ileal digestible (SID) lysine (protein) intakes and subsequent milk component yields. Sows were fed either 70, 100, or 130% of estimated SID lysine requirements from gestation day 90 and mammary biopsies were collected on day 110. The 70% treatment led to lower mRNA abundances of BCL2 (vs 100%; P < 0.05) and SLC7A7 and SLC7A9 (vs 130%; P < 0.05). Regardless of diet, mRNA abundances of SLC7A1 and CCND1 were positively correlated with colostrum dry matter and SLC3A2, SLC7A1, and ACACA were positively correlated with colostrum fat contents (P < 0.05). The mRNA abundance of SLC1A1 was negatively correlated with daily milk lactose yield, while SLC7A6 and CSN2 were positively correlated with milk yield, and dry matter, crude protein and lactose yields (P < 0.05). The mRNA abundance of LALBA was positively correlated with milk yield and lactose yield (P < 0.05). Therefore, SID lysine (protein) intake in late gestation minimally influenced mammary parenchymal mRNA abundances of select candidate genes, while subsequent yields of milk and milk components were related to milk protein and amino acid transporter genes.