The mammary gland is the organ in which biosynthesis and secretion of milk take place. These immunoglobulins are delivered to the neonate via sucking and afford passively acquired immunity. Immunoglobulins are key components that are necessary for the survival of the kid. It also presents some interesting components from a biological viewpoint, such as protective substances (immunoglobulins, lactoferrin and lysozymes) and growth factors (vitamins and amino acids) among others. Colostrum is characterized by high fat as well as protein and mineral contents compared with mature milk. Colostrum that is secreted initially by mammary gland after parturition differs markedly from mature milk. It occurs in the time of a particular physiological and functional stage of mammary gland development which is significantly distinct from the gland’s primary role of milk production. The initial secretion of mammary gland near or at the time of parturition is defined as colostrum.
The pregnancy that induce the changes of endocrine can stimulate the proliferation of mammary epithelial cells which will prepare for feracious milk production (Lactogenesis II) during Lactogenesis I.
The changes that happen during lactation, pregnancy and involution have been defined as Lactogenesis I (differentiation, growth and colostrogenesis), Lactogenesis II (feracious milk production) and involution (degradation to a nonlactating state).
The mammary glands of adult female goats have the ability to go through continual developmental series which are regulated by the endocrine system. The biological features of these miRNAs may help to clarify the molecular mechanisms of lactation and the development of caprine mammary gland. Our finding suggested that the profiles of miRNAs were related to the physiological functions of mammary gland in the colostrum and peak lactation periods. Chr5_3880_mature regulated mammary gland development and lactation through Serine/threonine-protein phosphatase (PPP1CA), which was in the oxytocin signalling pathway. In addition, the miRNA-target-network showed that the bta-miR-574 could influence the development of mammary gland and lactation by leptin receptor (LEPR), which was in the adipocytokine signalling pathway. Pathway analysis suggested that oestrogen, endocrine, adipocytokine, oxytocin and MAPK signalling pathways act on the development of mammary gland and milk secretion importantly. Their expression patterns were the same with Solexa sequencing results. The expressions of 10 randomly selected miRNAs was analyzed through stem-loop real-time quantitative PCR (RT-qPCR).
This study identified 131 differentially expressed miRNAs ( P 1 or log 2 colostrum NE/peak lactation NE 1 or log 2 colostrum NE/peak lactation NE < −1). A lot of high-throughput sequencing (HTS) research on miRNAs has been executed in the caprine mammary gland at different lactation periods (common milk lactation and dry period), but little is known about differentially expressed miRNAs in the caprine mammary gland of colostrum and peak lactation periods. MicroRNAs (miRNAs) have a great influence on various physiological functions.