The mammary gland in small ruminants: major morphological and functional events underlying milk production – a review

Abstract

The importance of small ruminants to the dairy industry has increased in recent years, especially in developing countries, where it has a high economic and social impact. Interestingly and despite the fact that the mammary gland is the specialised milk production organ, very few authors studied the modifications occurring in the mammary gland through the lactation period in production animals, particularly in the small ruminants, sheep (Ovis aries) and goat (Capra hircus). Nevertheless, understanding the different mammary gland patterns throughout lactation is essential to improve dairy production. In addition, associating these patterns with different milking frequencies, lactation number or different diets is also of high importance, directly affecting the dairy industry. The mammary gland is commonly composed of parenchyma and stroma, which includes the ductal system, with individual proportions of each changing during the different periods and yields in a lactation cycle. Indeed, during late gestation, as well as during early to mid-lactation, mammary gland expansion occurs, with an increase in the number of epithelial cells and lumen area, which leads to increment of the parenchyma tissue, as well as a reduction of stroma, corresponding macroscopically to the increase in mammary gland volume. Throughout late lactation, the mammary gland volume decreases owing to the regression of the secretory structure. In general, common mammary gland patterns have been shown for both goats and sheep throughout the several lactation stages, although the number of studies is limited. The main objective of this manuscript is to review the colostrogenesis and lactogenesis processes as well as to highlight the mammary gland morphological patterns underlying milk production during the lactation cycle for small ruminants, and to describe potential differences between goats and sheep, hence contributing to a better description of mammary gland development during lactation for these two poorly studied species.

Relationship between production conditions and milk gross composition in ewe’s and goat’s organic and conventional farms in central Greece

“…More specifically, lactose and protein contents were found to be higher in milk from other than native breeds. This may be related to mammary gland differences among breeds, such as anatomic particularities and different morphological patterns (Cadar et al 2012;Lerias et al 2014). Manual milking was associated with lower lactose content in ewe's milk.…”

The effect of colostrum period management on BW and immune system in lambs: from birth to weaning

“…In fact, colostrum contains a complex mixture of proteins that actively participate in the protection of the neonate (passive immune transfer (PIT)) against pathogens and other postpartum environmental challenges (Bendixen et al, 2011). Moreover, colostrum has diverse components such as fat, lactose, vitamins or minerals that have high nutritional importance (Ontsouka et al, 2003;Lérias et al, 2014;Hernández-Castellano et al, 2014b).…”

“…In fact, colostrum contains a complex mixture of proteins that actively participate in the protection of the neonate (passive immune transfer (PIT)) against pathogens and other postpartum environmental challenges (Bendixen et al, 2011). Moreover, colostrum has diverse components such as fat, lactose, vitamins or minerals that have high nutritional importance (Ontsouka et al, 2003;Lérias et al, 2014;Hernández-Castellano et al, 2014b).In particular, colostrum plays an important role in newborn lambs, because they are born hypogammaglobulinemic, † E-mail: noemi.castro@ulpgc.es Animal (2015), 9:10, pp 1672-1679 © The Animal Consortium 2015 doi:10.1017/S175173111500110X animal 1672 due to the complexity of the synepitheliochorial ruminant placenta, which does not allow sufficient transfer of immunoglobulins from the dam to the fetus (Hernández-Castellano et al, 2014a). In addition, it has been described that lambs not fed colostrum in the first hours of life are more susceptible to diseases and mortality (Ahmad et al, 2000;da Nobrega et al, 2005;Nowak and Poindron, 2006).…”

Use of proteomics in the study of microbial diseases of small ruminants

“…Currently, the terminology '-omics' refers to technologies, which explore roles of various molecules that make up the cells of an organism, their actions, as well as the relationships between them (Lérias et al, 2014). All these technologies are termed 'biomics', as they enable study of organisms at different levels (Athanasiadou and Huntley, 2008).…”