Maternal immunity plays a pivotal role in swine health and production because piglets are born agammaglobulinemic and with limited cell-mediated immunity, i.e. few peripheral lymphoid cells, immature lymphoid tissues, and no effector and memory T-lymphocytes. Swine do not become fully immunologically competent until about 4 weeks of age, which means that their compromised ability to respond to infectious agents during the first month of life must be supplemented by maternal immune components: (1) circulating antibodies derived from colostrum; (2) mucosal antibodies from colostrum and milk; and (3) immune cells provided in mammary secretions. Because maternal immunity is highly effective at protecting piglets against specific pathogens, strengthening sow herd immunity against certain diseases through exposure or vaccination is a useful management tool for ameliorating clinical effects in piglets and delaying infection until the piglets’ immune system is better prepared to respond. In this review, we discuss the anatomy and physiology of lactation, the immune functions of components provided to neonatal swine in mammary secretion, the importance of maternal immunity in the prevention and control of significant pathogens.

Objective of the study was to record, by means of ultrasonographic examination, changes occurring during lactogenesis in the udder of healthy ewes and of ewes with pregnancy toxaemia. The work was carried out in 28 ewes, 16 with pregnancy toxaemia (group A) and 12 healthy controls (group B). B-mode and Doppler ultrasonographic examination of the udder of ewes was performed. During the last month of pregnancy, grey-scale intensity values of mammary parenchyma in group A were significantly greater than in group B (P = 0·007), as was also the progressive increase in grey-scale intensity values in both groups (P < 0·001). Blood mammary input was significantly greater in ewes of group B than in ewes of group A (P < 0·05), as was also the progressive increase in blood input in both groups (P < 0·001). Further, differences between the two groups were identified in pulsatility index (P = 0·007) and in mean blood velocity (P = 0·036), but only during the last fortnight of pregnancy. After lambing, grey-scale values decreased sharply compared to those in pregnancy (P < 0·01), whilst blood input, pulsatility index and mean blood velocity continued the same trend as at the last stage of pregnancy, with differences between the two groups still prevalent (P < 0·05). There was a reverse correlation between grey-scale intensity values and milk quantities (P < 0·035) and a correlation between blood input and milk quantities (P < 0·07). The progressive increase in the diameter of the external pudendal artery was significant (P < 0·001), but no significant differences were evident between the two groups (P > 0·35). Differences between group A and group B in all other haemodynamic parameters studied were not significant, neither throughout the last month of pregnancy (P > 0·25), nor during the first week of lactation (P > 0·06). However, their progressive changes during the last month of pregnancy were significant (P < 0·02).

Colostrum provides newborn piglets with energy, immunoglobulins and growth, thereby playing an essential role in piglet survival. However, colostrum yield and composition are highly variable among sows. Some of the factors involved in this variability have been identified. The aim of the study was to confirm previous findings on a large number of animals and to investigate other potential factors of variation, such as the process of farrowing and the morphological changes of the mammary epithelium that occur during the 24 h postpartum. The experiment was conducted on 16 Large White (LW) and 56 Landrace (LR) × Large White (LR × LW) crossbred sows of mixed parities and their litters. Most farrowings were induced at 113 days of gestation and all farrowings were attended. Each piglet was weighed at birth and 24 h after farrowing started (t24). Colostrum ingestion by individual piglets was estimated using piglet weight gains from birth to t24. Colostrum production by sows was estimated by summing up colostrum intakes by each piglet of the litter. Colostrum was collected at the onset of farrowing (t0) and at t24 to determine concentrations of immunoglobulins G (IgG), Na and K. Analyses of correlations and multiple regressions were performed to identify the variables involved in variation of colostrum yield and IgG concentrations. Colostrum yield was not related to litter size and weight (P > 0.1). It was negatively correlated with the number of stillborn piglets (r = −0.33, P = 0.005) and within-litter variation of piglet birth weight (r = −0.24, P = 0.04). It was not related to the Na/K ratio in the colostrum, which is an indicator of the integrity of the mammary epithelium. When sows were categorised according to their level of colostrum yield, sows that produced a low yield of colostrum had more stillborn piglets at birth than the other sows (P < 0.05) and tended to have a longer birth interval during the early process of parturition (P < 0.1). At t24, concentrations of IgG in the colostrum were positively correlated with the Na/K ratio in the colostrum (r = 0.53, P < 0.001), which indicates the concomitance of the cessation of IgG transfer to the colostrum and the changes in the morphology of the mammary epithelium. This study points out the need for future research on the role of the hormones involved in both the process of parturition and lactogenesis in the relationship between stillbirth, process of parturition and colostrum production.

The aim of the study was to establish in vitro a bovine mammary epithelial cell (MEC) clone, able to respond to mitogenic growth factors and to lactogenic hormones. Mammary tissue from a 200-d pregnant Holstein cow was used as a source of MEC, from which a clone was established through a process of limiting dilution. When plated on plastic, the cells assumed a monolayer, cobblestone, epithelial-like morphology, with close contact between cells. Inclusion of IGF-1 and EGF in the media significantly increased the number of cells 5 d after plating. All cells stained strongly for cytokeratin and moderately for vimentin at young and old passage stages, indicating the epithelial nature of this cell clone. When the cells were plated at a high density on a thin layer of a commercial extracellular matrix preparation (Matrigel), lobular, alveoli-like structures developed within approximately 5 d, with a clearly visible lumen. When cells were plated onto Matrigel in differentiation media (containing lactogenic hormones), detectable quantities of α-casein were present in the media and particularly on the lumen side of the structures. Omission of one of the lactogenic hormones (insulin, prolactin or hydrocortisone) reduced α-casein release to the limit of detection of the assay used. Lactoferrin was also produced when the cells were plated on Matrigel, again principally on the lumen side of the lobules, though this was independent of the lactogenic hormones. By passage 40, the cells had senesced, and it was not possible to induce α-casein or lactoferrin production. This study notes the establishment of a functional bovine mammary epithelial cell clone, which is responsive to mitogenic and lactogenic hormones and an extracellular matrix.