Onset Of Lactogenesis Research Articles

Structured antenatal milk expression education for nulliparous pregnant people: results of a pilot, randomized controlled trial in the United States

BackgroundHand-expression, collection, and storage of breast milk during pregnancy (i.e., antenatal milk expression or AME) is a safe, potentially effective practice to reduce early, undesired infant formula supplementation among women with diabetes. The feasibility and potential impact of AME on lactation outcomes in the United States (U.S.) and among non-diabetic birthing people is unknown.MethodsThe purpose of this study was to examine the feasibility of a structured AME intervention among nulliparous birthing people in the United States. We recruited 45 low-risk, nulliparous individuals at 34–366/7 weeks of gestation from a hospital-based midwife practice. Participants were randomized to AME or a control group receiving lactation education handouts. Interventions were delivered at weekly visits at 37–40 weeks of pregnancy. The AME intervention involved technique demonstration and feedback from a lactation consultant and daily independent practice. Lactation outcomes were assessed during the postpartum hospitalization, 1–2 weeks postpartum, and 3–4 months postpartum.ResultsBetween December 2016 and February 2018, 63 individuals were approached and screened for eligibility, and 45 enrolled into the study (71%). Of 22 participants assigned to AME, 18 completed at least one AME study visit. Participants reported practicing AME on at least 60% of days prior to their infant’s birth. Most were able to express milk antenatally (15/18), more than half collected and froze antenatal milk (11/18), and 39% (7/18) supplemented their infants with antenatal milk after birth. No major problems were reported with AME. Perinatal and lactation outcomes, including infant gestational age at birth, neonatal intensive care unit admissions, delayed onset of lactogenesis II, and use of infant formula were similar between AME and control groups. Among participants in both groups who were feeding any breast milk at each assessment, breastfeeding self-efficacy increased and perceptions of insufficient milk decreased over the postpartum course.ConclusionsIn a small group of nulliparous birthing people in the U.S., AME education and independent practice beginning at 37 weeks of pregnancy was feasible. In some cases, AME provided a back-up supply of milk when supplementation was indicated or desired. The relationship between AME and lactation outcomes requires further study with adequately powered samples.Trial RegistrationThis trial was retrospectively registered at ClinicalTrials.gov on May 11, 2021 under the following registration ID: NCT04929301. https://clinicaltrials.gov/ct2/show/NCT04929301.

Oxytocin, Vasopressin and Prolactin in New Breastfeeding Mothers: Relationship to Clinical Characteristics and Infant Weight Loss.

Maternal milk production requires the neuropeptide oxytocin. Individual variation in oxytocin function is a compelling target for understanding low milk production, a leading cause of breastfeeding attrition. Complicating the understanding of oxytocin pathways is that vasopressin may interact with oxytocin receptors, yet little is known about the role of vasopressin in lactation. The aims of this study were (1) to describe maternal plasma oxytocin, vasopressin, and prolactin patterns during breastfeeding following low-risk spontaneous labor and birth in healthy first-time mothers and (2) to relate hormone patterns to maternal characteristics and breastfeeding measures. Eligible women were recruited before hospital discharge. Forty-six participants enrolled and 35 attended the study visit. Participants kept a journal of breastfeeding frequency, symptoms of lactogenesis, and infant weight. Plasma samples were obtained at breastfeeding onset on Day 4-5 postpartum, and repeated after 20 min. Hormones were measured with immunoassays. Infant weight change, milk transfer, and onset of lactogenesis were also measured. Baseline oxytocin and vasopressin were inversely related to one another. Oxytocin and prolactin increased significantly across the 20-min sampling period while vasopressin decreased. Higher oxytocin was associated with higher maternal age, lower BMI, shorter active labor, physiologic labor progression, and less weight loss in the newborn. Higher vasopressin correlated with younger maternal age, higher BMI, and greater newborn weight loss. Oxytocin and vasopressin have contrasting relationships with maternal clinical characteristics and newborn weight gain in early breastfeeding infants. Further study is needed to understand how oxytocin and vasopressin influence lactation outcomes.

Human milk mycotoxin contamination: smoking exposure and breastfeeding problems

Purpose: Mammalian milk may contain pollutants as a result of the maternal exposure. The objective was to determine the presence of selected mycotoxins in human milk and to investigate the effect of maternal characteristics on breastmilk mycotoxin levels and to examine the effect of mycotoxin contamination on lactational problems.Materials and methods: Information about maternal characteristics were taken by a questionnaire and breast milk samples were collected. Levels of aflatoxins M1 (AFM1), ochratoxins A (OTA), zearalenone (ZEN), Deoxynivalenol (DON) were determined by the solid-phase direct competitive enzyme immunoassay.Results: Median levels of breast milk AFM1 and OTA was 3.07 pg/mL and 1.38 ng/mL, respectively. ZEN and DON levels were higher than 0.3 ng/mL in 59% and higher than 10 ng/mL in 37.7%. After controlling for confounding factors, mothers who experienced “delayed onset of lactogenesis” had odds 3.33 times more for the highest quartile of ZEN and mothers with cracked nipples had odds 8.36 times more for the highest quartile of DON. Multiple regression analysis revealed that smoking exposure (environmental, maternal smoking versus never) significantly affected being in the highest quartile of OTA.Conclusion: Mycotoxin can pass to breast milk and smoking exposure of the mother may influence this situation. Mycotoxin exposure may lead to lactation problems. Maternal and infant health can be protected by preventing smoking exposure.

Effects of empowerment education on lactogenesis, psychological resilience and quality of life among patients with gestational diabetes

Objective To explore the effects of family-centered empowerment education on delayed onset of lactogenesis (DOL) , psychological resilience and quality of life among patients with gestational diabetes mellitus (GDM) . Methods From August 2017 to July 2018, we selected 160 GDM patients of department of obstetrics at a ClassⅢ Grade A hospital in Beijing as subjects by convenience sampling. A total of the 160 patients were divided into control group (odd numbers) and observation group (even numbers) according to the number based on time sequence of diagnosis of GDM, 80 cases in each group. Two groups all carried out routine health education for GDM patients. On that basis, observation group implemented family-centered empowerment education started from the diagnosis of GDM from 24 to 28 weeks of gestation one time per week until the end of delivery in hospital. The intervention effects were evaluated with the incidence of DOL, Connor-Davidson Resilience Scale (CD-RISC10) , WHO Quality of Life Scale Brief Version (WHOQOL-BREF) for patients between two groups. Results There were 76 cases in observation group and 72 cases in control group completing this study. The onset time of lactogenesis of observation group was (58.21±15.78) hours earlier than that of control group with a statistical difference (t=2.231, P<0.05) . The incidence of DOL of observation group and control group was 14.47% and 34.72% respectively with a statistical difference (χ2=8.235, P<0.05) . The total score of psychological resilience and quality of life of observation group was statistically higher than those of control group 42 days after childbirth (P<0.05) . Conclusions Family-centered empowerment education can make the onset time of lactogenesis ahead, reduce the incidence of DOL, and improve psychological resilience as well as quality of life of GDM patients. Key words: Diabetes, gestational; Lactation; Resilience, psychological; Quality of life; Delayed onset; Empowerment education

Correlation between the onset time of lactation period II and lactation yield of the early stage after delivery in preterm's mothers

Objective To analyze and explore the correlation between the onset time of lactogenesis Ⅱ and lactation yield of the early stage after delivery in preterm's mothers by continuously determining the lactation yield of the early stage after delivery in hospitalized preterm's mothers and the onset time of lactogenesis Ⅱin neonatal intensive care unit (NICU) . Methods We measured lactation yield and recorded the onset time of lactogenesis Ⅱ from 100 premature labour puerpera with hospital delivery of Obstetrics Department at a class Ⅲ grade A general hospital in Shandong Province. The relative factors of delayed onset of lactogenesis Ⅱ (DOL Ⅱ) were investigated with the preterm's mothers lactation-related factors comprehensive questionnaire and the Edinburgh Postnatal Depression Scale (EPDS) . Results The mean onset time of lactogenesis Ⅱ of hospitalized preterm's mothers in NICU were (68.23±26.42) hours. The incidence of DOL Ⅱ was 36% (36/100) . The onset time of lactogenesis Ⅱwas negatively related to the lactation yield 14 days after delivery (r=-0.525--0.354, P<0.01) . The lactation yield 14 days after delivery of onset delay group of lactogenesis Ⅱ was less than that of non-delayed group (Z=-4.89--3.10, P<0.01) . The influencing factors of DOL Ⅱ included whether they were combined with pregnancy-induced hypertension syndrome (OR=4.589, P<0.01) , hours of sleep (OR=0.649, P<0.01) and the first breast-feeding (OR=1.120, P<0.01) . Conclusions The incidence of DOL Ⅱ is high in hospitalized preterm's mothers of NICU. The DOL Ⅱ affects the lactation yield of the early stage after delivery in preterm's mothers. Medical workers should pay attention to the onset time of lactogenesis Ⅱ, correct pregnancy-induced hypertension syndrome in time, increase hours of sleep of puerpera and promote the first breast-feeding early enough so as to reduce or prevent the DOL Ⅱ and to improve the lactation condition of premature labour puerpera. Key words: Premature birth; Mothers; Yield; Onset time of lactogenesis Ⅱ

Research on the relationship between the adverse events during pregnancy and the delayed onset of lactogenesis

This article summarized and analyzed the researches on the relationship between the situation of pregnancy and onset time of lactogenesis to explore the relationship between the adverse events during pregnancy and delayed onset of lactogenesis, which aims to provide direction for clinical targeted preventive measures. Key words: Adverse events during pregnancy; Lactation; Correlation

Artificial Induction of Lactation in Bovines: Scope and Limitations

Estrogen, progesterone, prolactin and glucocorticoids work synergistically at the onset of lactogenesis. Estrogen stimulates mammary ductal growth, and the combination of estrogen and progesterone regulates lobular-alveolar development of the mammary gland. This development does not occur in infertile animal or animals suffering from reproductive disorders due to relative absence of sex steroid hormones. Artificial induction of lactation can be induced in such animals by the combination of steroid hormones estrogen and progesterone. Additionally reserpine (tranquilizer- increases prolactin level) and dexamethasone (a synthetic glucocorticoid) can be used in induction protocols to increase the success rate. Artificial induction reduces the involuntary culling rate as well as the genetic losses. To save such genetically superior bovines, induction of lactation is the most appropriate technology used under Indian conditions. The treatment is more effective in well-fed animals with good body condition score and having normal teat and udder. Hormonal induction of lactation should be practice only in infertile animals; it should not be followed as a routine practice, as an alternate to normal lactation. Estrogen and progesterone in 1:2.5 ratios is effective in exotic and cross bred while 1:1 ratio is effective in indigenous cows and buffaloes for artificial induction because of short luteal phase. These methods of artificial induction of lactation yield 60 to 70% milk of previous lactation.

Rankl Impairs Lactogenic Differentiation Through Inhibition of the Prolactin/Stat5 Pathway at Midgestation

Prolactin and progesterone both orchestrate the proliferation and differentiation of the mammary gland during gestation. Differentiation of milk secreting alveoli depends on the presence of prolactin receptor, the downstream Jak2-Stat5 pathway and the transcription factor Elf5. A strict regulation of Rank signaling is essential for the differentiation of the mammary gland and in particular for alveolar commitment. Impaired alveologenesis and lactation failure are observed in both, knockout and Rank overexpressing mice; however, the underlying molecular mechanism responsible for these phenotypes remains largely unknown. Using genome-wide expression analyses and functional studies, we show here that Rankl (RL) exposure leads to impaired secretory differentiation of alveolar cells not only in MMTV-RANK but also in wild-type (WT) mammary acini. Conversely, pharmacological blockage of Rank signaling at midgestation in WT mice leads to precocious and exacerbated lactogenesis. Mechanistically, RL negatively regulates Stat5 phosphorylation and Elf5 expression at the onset of lactogenesis. Continuous RL exposure leads to the expansion of basal and bipotent cells in WT and MMTV-RANK acini. Overall, we demonstrate that enhanced Rank signaling impairs secretory differentiation during pregnancy by inhibition of the prolactin/p-Stat5 pathway.

High Fat Diet Alters Lactation Outcomes: Possible Involvement of Inflammatory and Serotonergic Pathways

Delay in the onset of lactogenesis has been shown to occur in women who are obese, however the mechanism altered within the mammary gland causing the delay remains unknown. Consumption of high fat diets (HFD) has been previously determined to result decreased litters and litter numbers in rodent models due to a decrease in fertility. We examined the effects of feeding a HFD (60% kcal from fat) diet versus a low-fat diet (LFD; 10% kcal from fat) to female Wistar rats on lactation outcomes. Feeding of HFD diet resulted in increased pup weights compared to pups from LFD fed animals for 4 d post-partum. Lactation was delayed in mothers on HFD but they began to produce copious milk volumes beginning 2 d post-partum, and milk yield was similar to LFD by day 3. Mammary glands collected from lactating animals on HFD diet, displayed a disrupted morphologies, with very few and small alveoli. Consistently, there was a significant decrease in the mRNA expression of milk protein genes, glucose transporter 1 (GLUT1) and keratin 5 (K5), a luminobasal cell marker in the mammary glands of HFD lactating animals. Expression of tryptophan hydroxylase 1 (TPH1), the rate-limiting enzyme in serotonin (5-HT) biosynthesis, and the 5-HT7 receptor (HTR7), which regulates mammary gland involution, were significantly increased in mammary glands of HFD animals. Additionally, we saw elevation of the inflammatory markers interleukin-6 (IL-6) and tumor necrosis factor-α (TNF- α). These results indicate that consumption of HFD impairs mammary parenchymal tissue and impedes its ability to synthesize and secrete milk, possibly through an increase in 5-HT production within the mammary gland leading to an inflammatory process.

Timing of Stage II Lactogenesis Is Predicted by Antenatal Metabolic Health in a Cohort of Primiparas

Time to onset of stage II lactogenesis varies widely, and delayed onset of lactogenesis (OL) is common among first-time mothers in the United States. Higher body mass index, older age, and larger infant birth weight are identified risk factors for delayed OL; all are known correlates with glucose metabolism. Our objective was to prenatally assess maternal biomarkers related to metabolic health and determine the extent to which these biomarkers predict timing of OL. We enrolled a population-based sample of expectant primiparas attending a single prenatal clinic. We obtained a blood sample 1-hour post-glucose load from an antenatal oral glucose challenge test and assayed for the following biomarkers: serum insulin, glucose, adiponectin, leptin, C-reactive protein, interleukin-6, resistin, and tumor necrosis factor-α. Our outcome measure was timing of OL, based on maternal report at 3-5 days postpartum. We used linear regression to model OL hour. Twenty-six of 29 (90%) agreed to screening, 18 delivered at term and initiated breastfeeding, and 16 have complete data. Median (minimum-maximum) postpartum body mass index was 27.4 (21.8-34.7) kg/m(2), and median time to OL was 64 (10-121) hours. The model, OL = 232 - 34.9(ln[ratio insulin/glucose]) - 1.4(adiponectin), explained 56% of the variation in OL hour (p = 0.005) and was not weakened by potential confounders. Higher serum insulin secretion relative to serum glucose after a glucose challenge and higher serum adiponectin are associated with earlier onset of OL. These findings suggest that factors associated with better glucose tolerance predict earlier OL.

Excess Weight Loss in First-Born Breastfed Newborns Relates to Maternal Intrapartum Fluid Balance

The objectives were to describe weight loss in a multiethnic population of first-born, predominantly breastfed, term infants and to identify potentially modifiable risk factors for excess weight loss (EWL). Data on prenatal breastfeeding intentions, demographic characteristics, labor and delivery interventions and outcomes, breastfeeding behaviors, formula and pacifier use, onset of lactogenesis, and nipple type and pain were collected prospectively. Logistic regression analyses identified independent predictors of EWL (≥10% of birth weight) by using a preplanned theoretical model. EWL occurred for 18% of infants who received no or minimal (≤60 mL total since birth) formula (n = 229), including 19% of exclusively breastfed infants (n = 134) and 16% of infants who received minimal formula (n = 95). In bivariate analyses, EWL was associated (P < .05) with higher maternal age, education, and income levels, hourly intrapartum fluid balance, postpartum edema, delayed lactogenesis (>72 hours), fewer infant stools, and infant birth weight. In multivariate logistic regression analysis, only 2 variables predicted EWL significantly, namely, intrapartum fluid balance (adjusted relative risk for EWL of 3.18 [95% confidence interval [CI]: 1.35-13.29] and 2.80 [95% CI: 1.17-11.68] with net intrapartum fluid balance of >200 and 100-200 mL/hour, respectively, compared with <100 mL/hour) and delayed lactogenesis (adjusted relative risk: 3.35 [95% CI: 1.74-8.10]). EWL was more common in this population than reported previously and was independently related to intrapartum fluid balance. This suggests that intrapartum fluid administration can cause fetal volume expansion and greater fluid loss after birth, although other mechanisms are possible.

Delayed onset of lactogenesis among first-time mothers is related to maternal obesity and factors associated with ineffective breastfeeding

Delayed onset of lactogenesis (OL) is most common in primiparas and increases the risk of excess neonatal weight loss, formula supplementation, and early weaning. We examined variables associated with delayed OL among first-time mothers who delivered at term and initiated breastfeeding (n = 431). We conducted in-person interviews during pregnancy and at days 0, 3, and 7 postpartum and extracted obstetric and newborn information from medical records. We defined OL as delayed if it occurred after 72 h and used chi-square analysis to examine its association with potential risk factors across 6 dimensions: 1) prenatal characteristics, 2) maternal anthropometric characteristics, 3) labor and delivery experience, 4) newborn characteristics, 5) maternal postpartum factors, and 6) infant feeding variables. We examined independent associations by using multivariable logistic regression analysis. Median OL was 68.9 h postpartum; 44% of mothers experienced delayed OL. We observed significant bivariate associations between delayed OL and variables in all 6 dimensions (P < 0.05). In a multivariate model adjusted for prenatal feeding intentions, independent risk factors for delayed OL were maternal age > or =30 y, body mass index in the overweight or obese range, birth weight >3600 g, absence of nipple discomfort between 0-3 d postpartum, and infant failing to "breastfeed well" > or =2 times in the first 24 h. Postpartum edema was significant in an alternate model excluding body mass index (P < 0.05). The risk factors for delayed OL are multidimensional. Public health and obstetric and maternity care interventions are needed to address what has become an alarmingly common problem among primiparas.

Risk factors for early lactation problems among Peruvian primiparous mothers.

The aim of this study was to determine the incidence and risk factors for early lactation problems [suboptimal infant breastfeeding behaviour (SIBB), delayed onset of lactogenesis (OL) and excessive neonatal weight loss] among mother-infant pairs in Lima, Peru. All primiparous mothers who gave birth to a healthy, single, term infant at a government hospital in a peri-urban area of Lima during the 8-month recruitment period were invited to participate in the study. Data were collected at the hospital (day 0) and during a home visit (day 3). Infant breastfeeding behaviour was evaluated using the Infant Breastfeeding Assessment Tool; SIBB was defined as < or = 10 score. OL was determined by maternal report of breast fullness changes; delayed OL was defined as perceived after 72 h. Excessive neonatal weight loss was defined as > or = 10% of birthweight by day 3. One hundred seventy-one mother-infant pairs participated in the study. SIBB prevalence was 52% on day 0 and 21% on day 3; it was associated with male infant gender (day 0), < 8 breastfeeds during the first 24 h (days 0 and 3), and gestational age < 39 weeks (day 3). Delayed OL incidence was 17% and was associated with infant Apgar score < 8. Excessive neonatal weight loss occurred in 10% of neonates and was associated with maternal overweight and Caesarean-section delivery. Early lactation problems may be influenced by modifiable factors such as delivery mode and breastfeeding frequency. Infant status at birth and maternal characteristics could indicate when breastfeeding dyads need extra support.

Screening for hypoglycemia in healthy term neonates: effects on breastfeeding

Transient hypoglycemia in the early neonatal period is a common adaptive phenomenon as the newborn changes from the fetal state of continuous transplacental glucose consumption to intermittent nutrient supply following cessation of maternal nutrition at birth. Research has demonstrated that in the term, healthy newborn, this dynamic process is self-limiting and is not considered pathologic. The American Academy of Pediatrics and the World Health Organization recommend that neonatal blood glucose screening be reserved for newborns who are at risk or symptomatic and conclude that universal hypoglycemia screening is inappropriate, unnecessary, and potentially harmful. Nevertheless, many hospital nurseries continue the clinical practice of routine early glucose screening on healthy, term newborns. This results in the misidentification of neonates captured while experiencing the normal, self-correcting physiologic blood glucose nadir who are then diagnosed with pathologic neonatal hypoglycemia. Subsequent to this misdiagnosis, further surveillance and unnecessary, aggressive treatment interventions will follow that are potentially harmful to the successful establishment of positive maternal-infant interactions and the breastfeeding experience. Research studies indicate that routine hypoglycemia screens, treatments, and interventions in the healthy infant are not evidence-based and result in a serious disruption of the initiation process and duration patterns of lactation. Using the perspective of the theory of technology dependency, this inquiry explores the potential adverse sequelae of inappropriate glucose screening in the healthy breastfeeding newborn and describes selected outcome variables including: 1) the consequences of early maternal-infant separation, 2) the influence of early formula supplementation on breastfeeding discontinuance rates, 3) the effect of separation and supplementation on the onset of lactogenesis, and 4) the impact of hospital staff and provider recommendations of formula supplementation on maternal confidence to independently nurture her baby.

Regulation of the immunoglobulin G1 receptor: effect of prolactin on in vivo expression of the bovine mammary immunoglobulin G1 receptor.

Induction of colostrogenesis in non-pregnant cows was used to evaluate the relationship between prolactin (PRL) and mammary immunoglobulin G1 (IgG1) receptor expression. Six of eleven non-pregnant, non-lactating Holstein cattle responded to a standard lactation induction protocol by development of elevated IgG1 concentrations in mammary secretions. In order to increase the diversity in PRL concentrations, two of the six cattle were treated with bromocriptine, and two others were treated with recombinant bovine PRL. Serum alpha-lactalbumin, serum PRL and mammary secretion IgG1 concentrations were measured throughout the experiment. Biopsies of mammary tissue were collected after induction of lactation, and after treatments to alter serum PRL. Immunohistochemistry was used to evaluate IgG1 receptor expression. Administration of recombinant bovine (rbPRL) was associated with increased lactogenic activity, decreased secretion IgG1 concentrations, and decreased IgG1 receptor expression. Decreased serum PRL, due to bromocriptine, was associated with decreased lactogenic activity and maintenance of IgG1 receptor expression. Results of this experiment are consistent with an effect of PRL in decreasing the expression of the bovine mammary IgG1 receptor at the onset of lactogenesis.

The effects of exogenous progesterone supplementation in late pregnancy on gestation length and colostrum yield in ewes

The importance of falling progesterone (P4) concentrations in the initiation of parturition and the onset of lactogenesis in many species has long been recognised (Thorburn, et al., 1972). O'Doherty and Crosby (1996) reported a negative linear relationship between P4 concentration at 1 hour post lambing and colostrum yield at 1 h and total yield at 18 h. The administration of progesterone failed to delay parturition when given at a daily dose of 80 mg for a week but larger doses of progesterone (160 mg/day) blocked term labour in most sheep (Bengtsson and Schofield, 1963). The objective of this experiment was to examine the effects of exogenous progesterone administration to ewes in late pregnancy on ewe serum progesterone concentrations, gestation length and colostrum yield and quality.

Salivary oestriol and progesterone concentrations in women during late pregnancy, parturition and the puerperium.

Oestriol and progesterone concentrations were measured by specific radioimmunoassays in the saliva of six women on a daily basis during the last month of pregnancy, at frequent intervals during labour and daily during the puerperium. Salivary steroid concentrations are thought to reflect the circulating concentrations of the free hormone, and hence may be more biologically relevant than the total plasma concentration, or the urinary excretion of a metabolite. There was no sign of a fall in salivary oestriol or progesterone concentrations before the onset of labour. During the first and second stages, the concentrations fluctuated widely, perhaps due to alterations in uterine blood flow. After delivery of the placenta, hormone concentrations declined abruptly. Oestriol reached undetectable levels of less than 0.1 nmol/l within a day, whereas progesterone concentrations declined somewhat more slowly, approaching follicular-phase values after 2-3 days. This slower decline in the concentration of progesterone may be due to a leaching-out of the hormone from body fat stores. The absence of any prepartum progesterone withdrawal presumably explains the characteristic postpartum delay in the onset of lactogenesis.

Hormone changes in milk at the onset of lactogenesis and parturition in Friesland sheep

SUMMARYOestrone sulphate, progesterone, total protein, Na and K concentrations in mammary secretions of Friesland sheep have been determined from 11 days before until 8 days after parturition. Mammary secretions were obtained on most days for at least 1 week before parturition in 9 of 14 ewes, and in all animals after lambing. Oestrone sulphate concentration had doubled on the morning of parturition compared with the value 24 h earlier, and this sharp rise was a useful indicator that delivery was imminent. Values continued to rise during the day of delivery, remained high for a further 24 h and then declined over the next 2 days. Progesterone, in contrast, decreased linearly between day –2 and day +2 when it reached baseline values.Total protein concentration in pre-colostral and colostral mammary secretion (10–15 g/100 ml) was higher than that in goats, and decreased to a mean value of about 6 g/100 ml by day +8 after delivery. Na declined from about 55 mM on day –10 to 36 mM on day 0, whereas K increased from 20 to 29 mM. There was a sharp rise in K/Na, but this occurred after rather than before parturition and was not a useful predictor of parturition.The onset of copious milk secretion occurred when oestrone sulphate in mammary secretions was high and progesterone was low, which is consistent with the hypothesis that the cessation of progesterone secretion is an important regulator of the onset of lactogenesis in sheep. Efficiency of milk secretion in the first 14 days of lactation was correlated, however, with the maximum oestrone sulphate concentration in colostrum on the day of parturition.

Glutathione and gamma-glutamyl cycle enzymes in rat mammary gland.

The main enzymes of the gamma-glutamyl cycle during the lactogenic cycle in rat mammary gland were studied. A significant increase was found in all of them with the onset of lactogenesis. The effect of methionine sulfoximine on reduced glutathione concentration was studied in tissue slices of lactating mammary gland. The findings suggest that this compound effects glutathione synthesis by inhibiting gamma-glutamylcysteine synthetase.

Induction of lactation in dry dairy dattle.

Abstract Lactation was successfully induced in 14 of 15 non-pregnant cows treated for 7 days with twice daily subcutaneous injections of 15 mg oestradiol-17β and 37.5 mg progesterone. The successfully induced cows were first machine-milked about 8 days after the end of treatment and, although they milked for as long as their naturally calving identical twins, produced significantly less milk, fat and lactose. Augmenting the basic regimen with Opticortenol or thyrotrophin-releasing hormone produced no advantage. Plasma and milk hormone analyses were conducted and used to study the onset of lactogenesis and possible meat and milk residues. Ten of the 15 treated cows showed frequent oestrous activity and 4 became lame. Pregnancy rates after an 8-week insemination period were 69% and 93% for treated and control cows, respectively. It is concluded that the technique is unlikely to gain wide acceptance in the form used here.