Onset Of Lactation Research Articles

Estimates of Genetic Parameters for Daily Somatic Cell Count of Australian Dairy Cattle

Genetic parameters for daily somatic cell counts (SCC) of the first three parities were estimated for Australian Dairy Cattle. Most of the data analyses were carried out with a sire random regression model. The estimates were compared with those from conventional ten-trait analyses and animal models. In the first-parity estimates of heritabilities (h2) were low (0.04 to 0.05) at the beginning of the lactation and higher (0.11 to 0.13) at the end. The average h2 estimated from random regression sire model, random regression animal model and conventional multitrait sire model were 0.09, 0.09, and 0.08, respectively, in the first lactation. The average h2 were 0.09 and 0.11 in the second and third parities, respectively. Genetic correlations between daily loge SCC within parity were high for adjacent tests (nearly 1) and low (as low as 0.30) between the beginning and the end of the lactation. Generally, the genetic correlations between parities depend on how far apart they are and on whether they are on the same day in any two parities. Across parities, on average, genetic correlations between parities 1 and 3 were the lowest and those between 1 and 2 intermediate, while those between 2 and 3 were the highest. The estimated environmental correlations were lower than the genetic correlations, but the trends were generally similar. Differences in genetic parameter estimates due to model were small, except for some genetic correlations. The high residual error variances, the low h2, and the inconsistency in genetic correlations that were observed particularly at the beginning of the first lactation suggest that loge SCC early in the first lactation may be related to a spike in SCC as result of infection and (or) onset of lactation while SCC later in lactation represents a sustained response to infection. Accounting for the variation in heritabilities and correlations should improve the accuracy of genetic evaluations for SCC based on test day records.

Epidemiological evidence of effects of EDC on ruminant reproduction

Fifty percent of Dutch dairy farmers use surface water as the main source of drinking water for their cows during the grazing season. In many locations this surface water is in direct contact with a sewerage overflow. Belfroid and coworkers (1999) have demonstrated that this sewerage overflow surface water contains EDC, in particular xeno-oestrogens. The concentration of conjugated ethinyl-oestradiol, for example, in sewerage water was 0.02 mg/l. During the last decade the fertility of dairy cows has decreased dramatically. There is an increased incidence of cystic ovaries, an increase in the interval from calving to first insemination, an increase in the number of inseminations per pregnancy and more abortions have been recorded. These observations raise the possibility that EDC’s adversely affect reproduction in dairy cows. Meijer et al. (1999) compared the production and fertility of cows on 397 farms that used normal surface water with the production and fertility of cows on 60 farms that used water in direct contact with sewerage overflow. The results showed clearly that cows drinking water that was in direct contact with sewerage overflow produced less milk and had a greater age at first calving. Moreover they exhibited a tendency towards a longer interval between calving and first succesful insemination and tended to have a higher rate of abortions. Boerjan et al. (2001) have recently addressed the issues of concentrations of xeno-estrogens present in soil, in plants, in water and in cow tissues, milk and blood, in order to assess the potential risk to ruminants of xeno-estrogen exposure through soil and water ingestion. Although data are sparse and concentrations of EDC in feed and water of ruminant animals are low, under certain circumstances such as sewerage overflow and sludge-fertilized pasture, they concluded that rates of ingestion of certain xeno-oestrogens may exceed levels at which there is no effect. Since most EDC’s are lipophilic and become concentrated in adipose tissue, the mobilisation of fat during onset of lactation and pregnancy can expose animals to much higher concentrations of xeno-estrogens than are present normally in the environment. Important questions are: 1)how much of the EDC’s stored in fat cells will enter the blood under certain circumstances2)how much of the EDC’s in soil, water and plants will pass the rumen and enter also the blood and3)how potent are the different EDC’s i.e. what is the dose response relationship? In order to answer the last question an in vivo animal-model is urgently needed.We have developed an animal-model, based on the genital tract of an ovariectomized cow; the height and organisation of the endometrial lumen-epithelium, the rate of oedema in the stratum compactum and the electrical resistance of the cervical mucus are sensitive measures of oestrogenic activity.

Does ethnicity predict lactation? A study of four ethnic communities.

Human lactation is influenced by a variety of interrelated factors. The purpose of the study was to see whether the racial/ethnic factor is predictive of the onset of lactation and of the volume of breast milk. We planned a prospective study enrolling 269 women who were classified into four ethnic groups: Group 1 Arabs, Group 2 Africans, Group 3 Eastern Europeans, Group 4 Italians. Data regarding the women's habits, medical history and pregnancy were collected. After delivery we recorded the onset of lactogenesis and volume of milk output up until the fifth post-delivery day. A Cox model was fitted in order to assess the independent role that ethnicity has on the time to lactation; a general linear model was used to relate ethnicity to the overall amount of milk produced. Mean age was 27 years and was similar in all groups; half of the women were primiparae. All babies were exclusively breast-fed. Median time to lactation was 36 hours (20-36) and the median daily amount of milk produced was 173.5 ml (119-215). The earliest onset of lactation and the highest milk output was registered among Arab and Eastern European women. On Cox regression analysis ethnicity appeared to be an independent predictor of earlier lactogenesis: breast milk output occurred significantly earlier in the immigrant population than it did in the Italian population. No difference was observed among the immigrants. The multiple regression model showed that ethnicity independently predicts the overall amount of milk production: the Immigrant population produced a significantly higher milk output than the Italian population. No differences were observed within the immigrant groups. Ethnicity has been shown to be associated with the characteristics of breast-feeding. Further research is needed to understand the underlying mechanism.

The expression of the IGF family and GH receptor in the bovine mammary gland.

To study the involvement of the IGFs in mammary development and lactation of the cow, the temporal expressions of IGF-I and -II, its receptor type 1 (IGFR-1), IGF-binding proteins (IGFBPs)-1 to -6 and GH receptor (GHR) mRNA were examined. This was carried out for different stages of mammogenesis, lactogenesis, galactopoiesis and involution in the bovine mammary gland of 26 animals. Furthermore, IGF-I was localised by immunohistochemistry. The highest mRNA concentrations for IGF-I were detected in the mammary tissue of late pregnant heifers (days 255-272) and significantly lower expression was detected during lactogenesis and galactopoiesis. Immunohistochemistry of IGF-I revealed only a weak staining in the epithelium of the ducts during mammogenesis. The epithelium of the alveoli were negative during mammogenesis, lactogenesis and galactopoiesis but displayed distinct IGF-I activity during involution. In the stroma a distinct staining of the cytoplasm of adipocytes and of vascular smooth muscle cells was observed. A certain percentage of fibroblasts (usually 20-30%) were also immunopositive. In contrast, highest expression for IGFR-1 was detected during galactopoiesis and involution. The lowest mRNA concentration for IGFR-1 was found during pregnancy (days 194-213). In general, the expression of IGF-II was not regulated during mammogenesis and lactation, but decreased during involution. The mRNA for the six binding proteins was detected in the bovine mammary gland. The dominant binding proteins were IGFBP-3 and -5. The highest expression of IGFBP-3 was observed during mid-pregnancy and the lowest during late lactation, involution and in non-pregnant heifers. The mRNA for IGFBP-5 increased during late mammogenesis and lactogenesis followed by a decrease thereafter. In general, the mRNA concentrations for IGFBP-2, -4 and -6 were barely detectable during all stages. In contrast, the expression for IGFBP-1 was upregulated in the mammary gland of virgin heifers and increased around the onset of lactation. mRNA for GHR was found during all stages examined without outstanding fluctuations. In conclusion, locally produced IGF-I and -II may mediate mammogenesis. The high mammary IGFR-1 mRNA during lactation suggests a role for peripheral IGF-I in maintenance of lactation. The role of IGFBPs in the mammary gland needs further evaluation.

Maternal Perception of the Onset of Lactation Is a Valid, Public Health Indicator of Lactogenesis Stage II

Test weighing is the "gold standard" for documenting lactogenesis stage II. However, this method is impractical for use in population studies. Maternal perception of the timing of the onset of lactation may be a useful proxy for lactogenesis stage II. This study seeks to validate maternal perception of the onset of lactation as a marker of lactogenesis stage II. Women (n = 60) were recruited after cesarean delivery. Beginning at 24 h postpartum (pp), the onset of lactation was assessed 3 times daily by both test weighing and maternal perception. Delayed onset of lactation was defined as follows: 1) milk transfer < 9.2 g/feeding at 60 h pp and 2) maternal perception >/= 72 h pp. Misclassification analyses were conducted. Multivariate logistic regression, bivariate analyses and Cox survival analyses were used to evaluate the determinants and consequences of delayed onset of lactation, using both definitions. The sensitivity and specificity of delayed maternal perception as an indicator of delayed lactogenesis were 71.4 and 79.3%, respectively. Four risk factors for low milk transfer were significant (P: < 0.05) or nearly significant (P: </= 0.08) predictors of delayed perception of the onset of lactation. The effects of low milk transfer and delayed maternal perception on breast-feeding duration were similarly modified by intended breast-feeding duration. The magnitude and directionality of the ss coefficients for the milk transfer and perception variables were consistent. On the basis of these results, we conclude that maternal perception of the onset of lactation is a valid public health indicator of lactogenesis stage II.

Colostrum effects on the gastrointestinal tract, and on nutritional, endocrine and metabolic parameters in neonatal calves

Newborn calves are characterised by marked cardio-respiratory, metabolic and endocrine changes which continue during ensuing weeks and months. Thus, although the somatotrophic axis is basically functioning in neonatal calves, it is not yet mature. The speed of the adaptations of the various traits differs widely. The ability to digest colostrum and milk requires specific structures and functions of the gastrointestinal tract. Colostrum composition exhibits major changes after the onset of lactation. Colostrum intake is important for passive immunity, but also for the provision of carbohydrates, lipids, proteins, minerals and vitamins. In addition, colostrum contains hormones, growth factors, cytokines, enzymes, polyamines and nucleotides, which in the neonatal calf can exert biological effects. Thus, insulin-like growth factor I, which in colostrum is present in high amounts, may enhance gastrointestinal tract development and function of neonatal calves. Colostrum should be ingested as soon as possible after birth for efficient and sufficient absorption not only of immunoglobulins, but apparently also of (essential and non-essential) fatty acids and fat-soluble vitamins (β-carotene, retinol and α-tocopherol). The pattern of essential amino acids and the glutamine/glutamate ratio in blood plasma also greatly depend on whether and when colostrum is fed. In addition, there are considerable effects on hormones (especially on concentrations of insulin, glucagon, insulin-like growth factor-I, including its binding proteins, and cortisol) that are dependent on time and amount of colostrum fed.

Activation of NF-kappaB p50/p65 is regulated in the developing mammary gland and inhibits STAT5-mediated beta-casein gene expression.

The NF-kappaB family of transcription factors regulates diverse cellular functions such as immune response and cell growth and development, and has been reported to be constitutively active in a variety of mammary carcinoma cell lines. However, its role in normal mammary gland development has not been addressed. In our study, we detected developmentally regulated NF-kappaB activity in the mammary gland of mice. During pregnancy, DNA binding activity of NF-kappaB p50/p65 increased until day 16 postcoitum and decreased with the onset of lactation, most likely due to reduced p50 and p65 protein levels in the nucleus. Cotransfection experiments performed with 293 cells revealed an inhibition of the prolactin receptor/JAK2/STAT5 pathway by NF-kappaB. In HC11 cells, NF-kappaB p50/p65 activity was inversely correlated with prolactin-induced STAT5 tyrosine phosphorylation, expression of endogenous beta-casein gene, and of a transfected beta-casein gene promoter reporter construct. This indicates a negative cross talk between NF-kappaB and the prolactin receptor/JAK2/STAT5 activation pathway, which occurs at the level of STAT5 tyrosine phosphorylation. Our results provide evidence for a role of NF-kappaB in normal mammary gland development, and indicate its function as a negative regulator of beta-casein gene expression during pregnancy by interfering with STAT5 tyrosine phosphorylation.

Changes in mRNA Expression for Gluconeogenic Enzymes in Liver of Dairy Cattle During the Transition to Lactation

The objective of this study was to profile phosphoenolpyruvate carboxykinase (PEPCK) and pyruvate carboxylase (PC) mRNA expression in the liver of dairy cattle during the peripartum transition and determine changes in abundance of these mRNA in response to protein fed during the prepartum period. Thirty-eight multiparous Holstein cows were fed diets containing either 12% crude protein (CP) and 26% rumen undegradable protein (RUP), 16% CP and 26% RUP, 16% CP and 33% RUP, or 16% CP and 40% RUP on a dry-matter basis beginning 28 d before expected calving. After calving, all cows were fed a common diet through 56 d in milk (DIM). Northern analysis of RNA from liver biopsy samples obtained on days −28, −14, +1, +28, and +56 relative to calving indicated that PC and PEPCK mRNA expression were responsive to onset of lactation but not to prepartum protein or RUP concentration. Abundance of PEPCK mRNA was similar at −28, −14, and +1 DIM but was elevated by +28 and +56 DIM relative to precalving levels. Liver PC mRNA abundance was elevated on +1 DIM, remained elevated through 28 DIM, and declined to precalving levels by 56 DIM. The activity of PC enzyme was correlated (r2 = 0.89) with PC mRNA abundance. The data demonstrate increased abundance of PC mRNA during the early transition period followed by increased abundance of PEPCK mRNA during the postpartum period and suggest increased potential metabolism of lactate, pyruvate, and amino acids that contribute to the liver pyruvate pool.

A Homologous Radioimmunoassay for Quantification of Insulin-Like Growth Factor-Binding Protein-2 in Blood from Cattle

Insulin-like growth factor-I and -II (IGF-I, IGF-II) circulate in biological fluids bound to six different IGF-binding proteins that regulate IGF bioactivity. The IGF-binding protein-2 is regulated by growth hormones, and its concentration depends on nutrition and physiological state. Specific antibodies directed against bovine IGF-binding protein-2 were produced, and IGF-binding protein-2 levels in bovine blood samples were quantified by radioimmunoassay. Parallel displacement curves showed strong cross-reactivity with bovine and ovine plasma, were low with porcine plasma, and no cross-reactivity with rat or chicken plasma. Addition of IGF-I or -II to a control pool of bovine plasma did not significantly alter control IGF-binding protein-2 values in a radioimmunoassay. Six nycthemeral periods, determined for three young bulls bled on two occasions, showed that IGF-binding protein-2 plasma levels were stable throughout the day; two or three samples were sufficient to characterize the animal. Cows treated with recombinant bovine somatotropin (bST) had significantly lower serum levels of IGF-binding protein-2 than did control cows. Furthermore, IGF-binding protein-2 levels were dramatically increased at the onset of lactation. This radioimmunoassay for bovine IGF-binding protein-2, which enables quantitative assessment of IGF-binding protein-2 concentration in cattle, confirmed that IGF-binding protein-2 concentrations are depressed by administration of bST, enhanced after calving, and showed absence of diurnal variation.

The onset of lactation: implications for breast-feeding promotion programs.

This paper discusses the implications of the onset of lactation (OL) for breast-feeding (BF) promotion programs. It is noted that a delay in OL may lead to an early introduction of infant formula and an early termination of BF even after controlling for maternal original BF intentions. This is evinced by multivariate analyses performed on samples from different countries which consistently indicate that a delayed OL is a risk factor for poor BF outcomes. A longitudinal study conducted in urban Mexico found that OL was inversely associated with the likelihood of BF at 2 months post-partum (pp). In Honduras a cross-sectional survey among women with children 2 years old or younger indicated that OL > 72 hours pp was positively associated with the use of milk-based prelacteal feeds which was in turn associated with a lower likelihood of BF. A longitudinal study conducted in Hartford Connecticut USA found that the median BF duration among women with OL or = 72 hours pp. These data suggest that the longer it takes for women to perceive OL the more likely it is that they will become stressed and begin using breast milk substitutes. This may further delay OL leading to an early termination of BF. Future studies should emphasize the relationship between biological and psychosocial stress with OL and subsequent infant feeding outcomes.

Mammary gland immunology around parturition. Influence of stress, nutrition and genetics.

Adequate immune functions are essential for the defence against udder infections. Detailed knowledge about the immune response and important defence factors is essential in order to find new ways for the prevention and treatment of udder infections leading to mastitis. Work should be concentrated on ways of minimising the negative influence on immune functions and/or ways of stimulating these functions, especially during periods of immune suppression. A depression of important immune functions has been reported around parturition and there is a higher prevalence of clinical mastitis and other diseases during this period. Immunosuppression is often associated with high levels of glucocorticoids in blood, a common finding around parturition and during stressful conditions. A number of stressors are present around calving, e.g. parturition, onset of lactation and changes in feeding and management regimes. Adequate management including feeding strategies and routines are important for the immune functions. Metabolic stress as well as deficiencies in vitamins and minerals around parturition and during the first month of lactation can have a negative influence on the immune functions and thereby increase the risks for udder infections and mastitis. There seem to be a genetic variability in certain immune functions among periparturient cows. This might indicate a possibility to find markers for genetic selection of individuals with a well-developed immune system without negative effects on milk productivity.

Immunological aspects of pregnancy-associated glycoproteins.

The incidence of severe cases of acute E. coli mastitis in dairy cows is highest during early lactation. This phenomenon has been associated with a decreased function and decreased numbers of circulating polymorphonuclear neutrophil leukocytes (PMN). The cause of this impaired function and decreased number is poorly understood. Stress, hormonal and metabolic alterations around parturition and the onset of lactation may play a role in this phenomenon. Several molecules, such as cortisol and beta-hydroxybutyrate have been found to alter the oxidative burst activity of circulating PMN around parturition. Pregnancy-Associated Glycoprotein (bPAG) could also be involved. The theory of immunosuppression by bPAG was investigated because analogous glycoproteins produced by the placenta of other species exert local immunosuppression in order to maintain the histoincompatible feto-maternal unit. The production and subsequent release into the maternal circulation of bPAG is ensured by the binucleate cells from the trophoblast and starts already at implantation. However, peak levels are only reached 1 week before parturition. Due to the long half-life time of this molecule, high levels are found in plasma until 2 weeks after calving. The co-occurrence of the impairment of PMN oxidative burst activity in the early postpartum period and a peak in plasma bPAG concentrations might support the hypothesis of an immunosuppressive effect of PAG. Moreover, an inhibitory effect of bPAG on the proliferation of bovine bone marrow progenitor cells has been found recently in our laboratory. bPAG occurs in colostrum, but its effect on milk cells has not been clarified. It is concluded that interaction between the physiology of reproduction and lactation on the one side and immune function on the other side in dairy cattle requires further research.

Milk Ceruloplasmin and Its Expression by Mammary Gland and Liver in Pigs

Concentrations of ceruloplasmin and copper in milk and blood plasma, the nature of milk ceruloplasmin, and the effects of lactation and gestation on these parameters, as well as the expression of ceruloplasmin mRNA by the mammary gland, were examined in pigs. As seen previously in humans, ceruloplasmin and copper concentrations in sow milk were much higher a few days after birth than 1 month later, averaging 26.5 and 6.6 mg ceruloplasmin/L (by immunoassay) and 1.67 and 0.34 mg total Cu/L, on days 3 and 33 postpartum, respectively. Values for ceruloplasmin oxidase activity (measured with p-phenylene diamine) were 7.8 and 1.3 nmol/min/L, respectively. Daily milk ceruloplasmin production went from 61 to 22 mg/day and daily copper output from 38 to 12 mg/day. In contrast, there was little or no variation in serum ceruloplasmin concentration during lactation or gestation, although total plasma copper was high at the end of gestation. Milk ceruloplasmin was of the same apparent size as serum ceruloplasmin, as determined by SDS–PAGE and immunoblotting, and ceruloplasmin mRNAs of liver and mammary gland were indistinguishable by Northern analysis and RT-PCR of the various exons. Expression of total RNA and ceruloplasmin mRNA, as detected in biopsies of mammary gland, increased markedly upon onset of lactation and then declined during the next month in conjunction with a drop in milk ceruloplasmin production. The results indicate that milk ceruloplasmin, while being the same protein as in plasma, is not derived from the plasma but is produced by the mammary gland.

Does delayed perception of the onset of lactation shorten breastfeeding duration?

This longitudinal study evaluated the impact of the timing of maternal perception of the onset of lactation on breastfeeding duration. Breastfeeding mothers who delivered a full-term infant were interviewed daily from day 1 postpartum until the onset of lactation. Women were recontacted to determine the duration of any breastfeeding at 6.7 months postpartum, and if necessary, at 16.2 months postpartum. Cox survival multivariate analyses indicated that among women planning to breastfeed for at least 6 months, those with onset of lactation < 72 hours postpartum were likely to breastfeed longer than their counterparts with a delayed onset of lactation. Median breastfeeding durations were 11.7 months and 3.4 months, respectively (p < 0.00001). Among women who intended to breastfeed for less than 6 months, the timing of the onset of lactation did not influence breastfeeding duration. All analyses controlled for body build, delivery method, employment status, education, parity, and maternal age. These findings suggest that a delayed onset of lactation is likely to be associated with a shorter breastfeeding duration. This relationship, however, was modified by the mother's intended breastfeeding duration.

Hypocalcemia induced by intravenous administration of disodium ethylenediaminotetraacetate and its effects on excretion of calcium in urine of cows fed a high chloride diet.

Evidence supports the theory that a diet that is rich in nonmetabolizable anions fed to dairy cows during the dry period reduces the risk of hypocalcemic paresis puerperalis. When cows are fed a diet that is rich in anions instead of cations, more Ca is absorbed in the intestine and excreted in urine. We hypothesized that, in cows fed a diet that was rich in anions, the increased flow of Ca through the body could be drained to support the maintenance of plasma Ca concentration around parturition. The hypothesis was tested by binding plasma Ca through intravenous administration of Na2-EDTA and measuring excretion of Ca in urine. In a 2-period x 14-d crossover study, six, nonpregnant, nonlactating, multiparous cows were fed either a diet that was rich in cations (dietary cation-anion difference = +332 meq/kg of dry matter) or rich in anions (dietary cation-anion difference = -230 meq/kg of dry matter). On the last day of each feeding period, Na2-EDTA was infused intravenously until the amount of plasma Ca that was not bound to EDTA reached approximately 1 mmol/L. The amount of EDTA that could be infused was significantly greater when the cows were fed the diet that was rich in anions. During the infusion of Na2-EDTA the rate of Ca excretion in urine dropped to almost 0 when the diet that was rich in anions was fed. After feeding the diet that was rich in cations, excretion of Ca in urine was negligible and was not reduced further by Na2-EDTA infusion. Thus, in cows fed a diet that was rich in anions, the Ca intended for excretion with urine can be used when plasma Ca is under stress as would occur at the onset of lactation. However, the amount of Ca derived from plasma, interstitial fluid, and the skeleton during Na2-EDTA infusion was quantitatively much more important to the supply of Ca than was the reduction in excretion of Ca in urine. Most likely, this relationship would also be true when the production of colostrum begins.

Identification of Risk Factors for Delayed Onset of Lactation

Objective To identify infant feeding, socioeconomic, demographic, and delivery-related factors that affect women's self-reported timing of the onset of lactation. Design Longitudinal survey of women from day 1 postpartum until self-reported onset of lactation. Subjects were interviewed in person on day 1 postpartum, then surveyed daily by telephone regarding infant feeding method, breast symptoms, and perception of whether the onset of lactation had occurred. Medical records were reviewed. Subjects/setting Data were collected from 192 women after they gave birth to a healthy, term singleton. Statistical analyses performed χ 2 Analyses were used to identify variables associated with delayed onset of lactation (onset of lactation ≥72 hours postpartum). Multivariate logistic regression was used to identify the independent association of each significant variable with delayed onset of lactation. Results Risk factors for delayed onset of lactation included white/Hispanic ethnicity, heavy/obese body build, delivery of offspring by unscheduled cesarean delivery, vaginal delivery with prolonged stage 2 labor, infant birth weight less than 8 lb, and exclusive formula-feeding before the onset of lactation. Applications/conclusions Women who are at risk for delayed onset of lactation need additional breast-feeding support during the first week postpartum. During their hospitalization, these women should be instructed about the normal lactation process and the possibility that onset of lactation may occur later than 72 hours postpartum. Frequent nursing should be recommended, as delayed onset of lactation was associated with the lack of infant suckling. JAm Diet Assoc. 1999;99:450-454.

Changing nursing practice through research utilization: Consistent support for breastfeeding mothers

This research utilization project was designed to increase staff nurse support for four early postpartum breastfeeding practices: initiation in the delivery room, high frequency feedings, unlimited suckling time, and no supplementation. Research links these practices with lower neonatal bilirubin values and an earlier onset of lactation. An organizational approach to research utilization was taken to encourage nurses to support mothers in the desired breastfeeding practices. A before and after design was used to evaluate the extent to which the intended patient outcomes were achieved with the practice changes. The percent of infants having bilirubin tests decreased significantly. No significant differences were observed in mean bilirubin levels, incidence of hyperbilirubinemia, or lactation onset. The project promoted state-of-the-science nursing care and helped our nurses become more adept in using research to guide practice.

Energy Intake and Glycemia in Lactating Women with Type 1 Diabetes

Objective To describe glycemia and insulin administration in lactating women with type 1 diabetes and compare their energy intake, lactation onset, and postpartum weight to lactating women without diabetes. Design A prospective observational study conducted at 2, 3, 6, 14, 42, and 84 days postpartum. Insulin dosage and glucose levels after fasting and at 80 and 110 minutes after eating (by measuring capillary blood glucose concentrations and glycated hemoglobin [HbA 1c] values) are described for women with type 1 diabetes. Dietary intake, weight, and lactation onset for women with type 1 diabetes are compared with those without the disease. Subjects/setting Fourteen lactating women with type 1 diabetes and 25 women without diabetes (control subjects) were recruited from private obstetrician offices and high-risk prenatal clinics at 3 major medical centers. Statistical analyses A repeated-measures 2-factor analysis of variance was used to determine group, time, and interaction effects between women with type 1 diabetes and the control group at 2, 3, 7, 14, 42, and 84 days postpartum. Results Seven women with type 1 diabetes breast-fed through 84 days postpartum, although they perceived later onset of milk and had fasting and postprandial hyperglycemia. Their HbA 1c levels increased by 20%, confirming relative hyperglycemia. After adjustment for prepregnancy weight, women with type 1 diabetes consumed 7 kcal fewer per kilogram per day than control subjects. Average insulin dose was returned to prepregnancy levels of 45.3±3.6 U/d (least square means±standard error of the mean) by 1 week. Application Achieving desired metabolic control during the establishment of lactation is difficult. A better understanding of energy and insulin needs and their relationship to lactation in women with type 1 diabetes is needed. J Am Diet Assoc. 1998; 98: 642–648.

Effects of cabergoline on reproduction in three families of Australian marsupials.

The effects of the prolactin inhibiting drug, cabergoline, on pregnant and lactating marsupials were investigated in four species from three diverse families: the tammar wallaby, Macropus eugenii, the quokka, Setonix brachyurus, the brushtail possum, Trichosurus vulpecula, and the fat-tailed dunnart, Sminthopsis crassicaudata. In tammar wallabies, 20 micrograms cabergoline kg-1 injected intramuscularly 1 day before expected birth did not alter the timing of parturition but neonates died within a day of birth, suggesting that the onset of lactation was compromised. During early lactation in tammars (56-69 days post partum), an intramuscular injection transiently retarded growth of the young, although they subsequently survived. This treatment induced reactivation of the quiescent corpus luteum and the blastocyst from diapause, so a new birth occurred 26-27 days later, despite the continued sucking of the young in the pouch. Intramuscular injection during late lactation (166-199 days post partum) apparently suppressed milk secretion since pouch young lost up to 20% of their bodyweight or died within 7 days of treatment. Oral administration of cabergoline had no effect on the growth of the young or on the quiescent corpus luteum and diapausing blastocyst. Quokkas showed similar responses to tammars after treatment in late lactation. Possums and dunnarts were less sensitive to injected cabergoline than the two macropodid species, and possums showed no response to oral administration. The lack of response of these marsupial species to oral cabergoline treatment suggests that accidental ingestion of baits, containing 20 micrograms cabergoline kg-1, used to control introduced eutherian pests such as the red fox, Vulpes vulpes, or the feral cat, Felis cattus, should not affect the reproduction of native marsupials.

Cross-fostering study of methyl mercury retention, demethylation and excretion in the neonatal hamster.

The cross-fostering technique was used in order to compare methyl mercury (MeHg) metabolism in hamsters following prenatal (in utero) and neonatal (lactational) exposure. Pregnant Syrian golden hamsters were administered radiolabeled MeHg on day 12 of gestation. The offspring was nursed by foster mothers unexposed to MeHg, while the pups from the unexposed animals were nursed by the MeHg-administered animals. Under these conditions, each pup in the litter received a dose of MeHg in utero corresponding to 0.9% of the maternal dose. The average amount of mercury found in the pups exposed via milk corresponded to 4.5% of the total body burden of the foster dam at the onset of lactation. This was about half the amount received by the pups exposed in utero. The total body burden of mercury, and the amount of mercury in the liver, brain and kidney of the pups exposed in utero began to decrease at seven days of age. The rate of decrease differed among the tissues and was lowest in the kidney. The amount of mercury in pups exposed via milk reached a peak level when the pups were 10-15 days old. The total body burden of mercury showed a slow decrease while the liver, brain and kidney levels decreased rapidly. In both groups of animals, up to 80% of the total body burden of mercury was found in the pelt. These data show that milk may be a significant exposure route for mercury and that neonatal hamsters are unable to demethylate MeHg and excrete mercury in urine and faeces.