Nucleic Acid, Metabolic and Histological Changes in Gilt Mammary Tissue during Pregnancy and Lactogenesis

Abstract

Changes in mammary gland histology, dry weights, nucleic acids and in vitro rates of substrate oxidation in incorporation into lipid were measured in mammary biopsies of three gilts each on d 30, 45, 60, 75, 90, 105 and 112 of pregnancy, and d 1 and 4 of lactation. Histological changes noted were progressive duct growth early in pregnancy followed by rapid lobulo-alveolar development between d 75 and 90 to complete mammogenesis. Colostrum and lipid were evident by d 105 with marked distension of alveolar lumina on d 112. Complete differentiation of the secretory process was apparent on the day of parturition. Concentrtion of dry, fat-free tissue (DFFT) and DNA changed little before d 60 but increased fourfold between d 75 and 90. No further increases in DFFT or DNA were noted. RNA concentrations paralleled DNA through d 90, after which they steadily increased. Rates of acetate and glucose oxidation increased transiently during midpregnancy then declined and remained low until initiation of lactogenesis. Substrate incorporation into lipid increased slightly at midpregnancy and again at d 105, after which it increased markedly. Collectively, results indicate that mammogenesis is complete by d 90, after which lactogenesis is initiated in a two-stage process. Metabolic rates expressed on a DNA basis indicated considerable rates of oxidation, but not of lipogenesis by proliferating mammary tissue. Preferential metabolism of acetate vs glucose near parturition suggests coordination of metabolism between the mammary gland and other maternal tissues.

Changes in back fat thickness during late gestation predict colostrum yield in sows

“…As we did not collect more data between D85 and D109 of gestation, we can only propose some hypotheses that might explain this association. The period between D85 and D109 of gestation is considered to be important for mammogenesis (Kensinger et al, 1982;Ji et al, 2006), which was suppressed by keeping sows in an anabolic state during this period (Weldon et al, 1991). Our study population was mainly catabolic between D85 and D109 of gestation and there is no information available to date whether this benefits gestational mammogenesis.…”

Suckling effects in sows: importance for mammary development and productivity

“…The rate of accretion of mammary tissue and DNA increases thereafter four-to six-fold (Sorensen et al, 2002) so that by the time the gilt is mated, mammary glands are still very small but contain an extensive duct system with various budlike outgrowths (Turner, 1952). In pregnant gilts, quantitative development of the mammary glands is slow in the first two-thirds of gestation, while almost all accumulation of mammary tissue and DNA takes place in the last third (Hacker and Hill, 1972;Kensinger et al, 1982;Sorensen et al, 2002). During this period of rapid mammary development, mammary glands undergo major histological changes as the adipose and stromal tissues are replaced by lobuloalveolar tissue to become the milk secretory apparatus (Hacker and Hill, 1972;Kensinger et al, 1982;Ji et al, 2006).…”

“…During this period of rapid mammary development, mammary glands undergo major histological changes as the adipose and stromal tissues are replaced by lobuloalveolar tissue to become the milk secretory apparatus (Hacker and Hill, 1972;Kensinger et al, 1982;Ji et al, 2006). Between days 90 and 105, abundant secretion accumulates in the mammary alveoli, indicating the onset of the lactogenic process (Kensinger et al, 1982). Interestingly, location of the gland on the udder affects its development during gestation.…”

“…In pregnant gilts, quantitative development of the mammary glands is slow in the first two-thirds of gestation, while almost all accumulation of mammary tissue and DNA takes place in the last third (Hacker and Hill, 1972;Kensinger et al, 1982;Sorensen et al, 2002). During this period of rapid mammary development, mammary glands undergo major histological changes as the adipose and stromal tissues are replaced by lobuloalveolar tissue to become the milk secretory apparatus (Hacker and Hill, 1972;Kensinger et al, 1982;Ji et al, 2006). Between days 90 and 105, abundant secretion accumulates in the mammary alveoli, indicating the onset of the lactogenic process (Kensinger et al, 1982).…”

Pregnancy recognition signals in mammals: the roles of interferons and estrogens

“…However, PRL and P4 affect secretory activity of uterine GE and placental transport of nutrients in pigs (see Goldstein et al, 1976;Knight et al, 1977;Bazer et al, 1981;Young et al, 1990). In terms of mammogenesis and lactogenesis in pigs, E2, P4, PRL and possibly RLX affect mammogenesis between days 20 and 30, Stage I lactogenesis (around day 90) and Stage II lactogenesis (day 110) of the 114 day period of gestation (Kensinger et al, 1980).…”