Effects of increasing the dietary contents of metabolizable energy and protein during the peripartum period on mammary gland development in Sistani goats

The experiment was designed to consider effects of different amounts of metabolizable energy and protein on mammary gland development, mRNA abundance of genes related to vascular function and angiogenesis of Sistani goats. A total of 32 pregnant Sistani goats were selected on day 100 of gestation and allocated randomly to four treatments: (1) basal diet that meets metabolizable energy (ME) and protein (MP) requirements of goats during late gestation, as recommended by the National Research Council = NRC (2007) (C). (2) A diet with 10% higher levels of ME than recommendations (E). (3) A diet with 10% higher levels of MP than recommendations (P), and (4) a co-addition diet with 10% higher levels of both ME and MP than recommendations (EP). The four diets were fed from 100 days prepartum to 30 days after parturition. Mammary biopsies were obtained 24 h after parturition. Feed intake (g/day), colostrum (kg/day) and milk (kg/month) productions increased when extra E and P were provided together prepartum and early postpartum (P < 0.05). Relative mRNA abundances of vascular endothelial growth factor (VEGF, 4.68-fold), tyrosine kinase tie2 receptor (RTK, 4.61-fold), vascular endothelial growth factor receptor 1 (VEGFR1, 5.15-fold), angiopoietin I (ANGPT1, 4.86-fold), cyclooxygenase I (COX1, 4.5-fold), prostacyclin synthase (PTGIS, 5.66-fold), thromboxane A2 synthase (TBXAS, 98-fold) increased significantly in the mammary gland with the co-addition of E and P. Histological results documented that alveolar area (epithelium + luminal space, µm2), average number of epithelial cells per alveolus, and relative area occupied by overall epithelial cells (per slide) were increased significantly, when co-addition of E and P were fed in late gestation. In summary, increasing the dietary supply of ME and MP peripartum resulted in greater milk production, stimulated mammary gland alveolar development and affected the mRNA abundance of genes associated with both angiogenesis and milk secretion in Sistani goats.