Showing papers on "Lactation published in 2013"

Elevated non-esterified fatty acids and β-hydroxybutyrate and their association with transition dairy cow performance.

Abstract: Dairy cows pass through a period of negative energy balance as they transition from late gestation to early lactation. Poor adaptation through this period, expressed as excessively elevated concentrations of non-esterified fatty acids (NEFAs) pre- or post-partum and elevated concentrations of β-hydroxybutyrate post-partum, increases an individual animal's risk of post-partum disease, removal from the herd, reproductive difficulty, and reduced milk production. Field studies have shown that subclinical ketosis often affects 40% of cows in a herd although the incidence can be as high as 80%. Peak incidence occurs at 5 days in milk, and cows that develop subclinical ketosis in the first week of lactation have a higher risk of negative effects and reduced milk production than cows that develop subclinical ketosis in the second week of lactation. Herds with more than a 15-20% prevalence of excessively elevated concentrations of NEFAs and β-hydroxybutyrate in early lactation have higher rates of negative subsequent events, poorer reproduction, and lower milk yield than herds with a lower prevalence of negative energy balance. This paper reviews (1) strategies for testing of energy-related metabolites, (2) consequences of poor adaptation to negative energy balance (for individual animals and for herds), (3) treatment approaches for affected cows, and (4) economic considerations for testing and treating cows with poor adaptation to negative energy balance.

Anatomy of the human mammary gland: Current status of knowledge

Abstract: Mammary glands are unique to mammals, with the specific function of synthesizing, secreting, and delivering milk to the newborn. Given this function, it is only during a pregnancy/lactation cycle that the gland reaches a mature developmental state via hormonal influences at the cellular level that effect drastic modifications in the micro- and macro-anatomy of the gland, resulting in remodeling of the gland into a milk-secretory organ. Pubertal and post-pubertal development of the breast in females aids in preparing it to assume a functional state during pregnancy and lactation. Remarkably, this organ has the capacity to regress to a resting state upon cessation of lactation, and then undergo the same cycle of expansion and regression again in subsequent pregnancies during reproductive life. This plasticity suggests tight hormonal regulation, which is paramount for the normal function of the gland. This review presents the current status of knowledge of the normal macro- and micro-anatomy of the human mammary gland and the distinct changes it undergoes during the key developmental stages that characterize it, from embryonic life through to post-menopausal age. In addition, it discusses recent advances in our understanding of the normal function of the breast during lactation, with special reference to breastmilk, its composition, and how it can be utilized as a tool to advance knowledge on normal and aberrant breast development and function. Finally, anatomical and molecular traits associated with aberrant expansion of the breast are discussed to set the basis for future comparisons that may illuminate the origin of breast cancer.

RNA Sequencing of the Human Milk Fat Layer Transcriptome Reveals Distinct Gene Expression Profiles at Three Stages of Lactation

Abstract: Aware of the important benefits of human milk, most U.S. women initiate breastfeeding but difficulties with milk supply lead some to quit earlier than intended. Yet, the contribution of maternal physiology to lactation difficulties remains poorly understood. Human milk fat globules, by enveloping cell contents during their secretion into milk, are a rich source of mammary cell RNA. Here, we pair this non-invasive mRNA source with RNA-sequencing to probe the milk fat layer transcriptome during three stages of lactation: colostral, transitional, and mature milk production. The resulting transcriptomes paint an exquisite portrait of human lactation. The resulting transcriptional profiles cluster not by postpartum day, but by milk Na:K ratio, indicating that women sampled during similar postpartum time frames could be at markedly different stages of gene expression. Each stage of lactation is characterized by a dynamic range (105-fold) in transcript abundances not previously observed with microarray technology. We discovered that transcripts for isoferritins and cathepsins are strikingly abundant during colostrum production, highlighting the potential importance of these proteins for neonatal health. Two transcripts, encoding β-casein (CSN2) and α-lactalbumin (LALBA), make up 45% of the total pool of mRNA in mature lactation. Genes significantly expressed across all stages of lactation are associated with making, modifying, transporting, and packaging milk proteins. Stage-specific transcripts are associated with immune defense during the colostral stage, up-regulation of the machinery needed for milk protein synthesis during the transitional stage, and the production of lipids during mature lactation. We observed strong modulation of key genes involved in lactose synthesis and insulin signaling. In particular, protein tyrosine phosphatase, receptor type, F (PTPRF) may serve as a biomarker linking insulin resistance with insufficient milk supply. This study provides the methodology and reference data set to enable future targeted research on the physiological contributors of sub-optimal lactation in humans.

Lactation Biology Symposium: The effect of nutrient intake from milk or milk replacer of preweaned dairy calves on lactation milk yield as adults: a meta-analysis of current data.

Abstract: Data from calf studies conducted over the past 20 yr has shown that preweaning nutrient intake, from milk or milk replacer, can have profound effects on development of the calf that enhance first lactation and lifetime productivity. Many of the studies show positive but not significant effects of preweaning nutrition on long-term productivity, primarily due to a lack of power, usually due to inadequate animal numbers per treatment. Meta-analyses were conducted using Comprehensive Meta-Analysis (CMA) software (version 2.2.064; Biostat, Englewood, NJ; Borenstein et al., 2005) to evaluate the effects of preweaning nutrient intake and preweaning ADG on first lactation milk production from studies where milk yield and preweaning treatment data were adequately described. Currently, 12 studies have been reported, describing milk yield of calves that had been fed various levels of preweaning nutrients, from both milk and milk replacer, and 11 evaluated the effect of preweaning ADG on long-term productivity. The estimated effect size for treatment (level of milk or milk replacer intake) and ADG were calculated. Using a random effects model, the overall milk yield response based on treatment was 435 ± 117 kg/lactation (P < 0.001), demonstrating that among the data sets milk yield in the first lactation was increased by increasing nutrient intake from milk or milk replacer in preweaned calves. Meta-regression of the effect of ADG resulted in the following equation: milk yield = -106 kg + 1,551.4 kg × ADG (kg/d; P = 0.01) indicating that for every kilogram of preweaning ADG, first lactation milk yield increased by 1,550 kg. Furthermore, the meta-analysis yielded an odds ratio of 2.09 (P = 0.001) indicating that calves fed for greater preweaning ADG were 2 times more likely to have greater milk yield in the first lactation. Finally, the 2001 Dairy NRC calf model was used to estimate the difference, within study, of intake over maintenance from milk replacer, using either the actual data or the published ADG; the difference in intake over maintenance was used as a predictor in a meta-regression and resulted in the following equation: milk yield = -60 kg + 1,100 kg × estimated difference in intake over maintenance (P = 0.02). The data demonstrate that nutrient intake from milk or milk replacer during the preweaning period positively impacted long-term productivity of dairy calves and provides new management opportunities to improve milk yield of dairy cattle. These data appear to indicate that there are significant developmental functions being programmed in the neonatal calf that require further investigation.

Cells in Human Milk State of the Science

Abstract: Reflecting millions of years of adaptation and optimization, milk is unique to the species that produces it and for the young of which it is intended, with large variations in both lactation strategies and milk composition existing among different mammalian species. Despite this, milk has the consistent function of providing nourishment, protection, and developmental programming to the young, with short- and long-term effects. Among its components that confer these functions, breast milk contains maternal cells, from leukocytes to epithelial cells of various developmental stages that include stem cells, progenitor cells, lactocytes, and myoepithelial cells. Although in the first 150 years since their discovery, breast milk cells were mostly studied for their morphological traits, technological advances in the last decade have allowed characterization of breast milk cell types at the protein and messenger RNA levels. This is now paving the way for investigation of the functions of these cells in the breastfed infant and the use of breast milk as a tool to understand the normal biology of the breast and its pathologies. This review summarizes the current knowledge of breast milk cellular heterogeneity and discusses future prospects and potential applications.

High levels of anti-inflammatory and pro-resolving lipid mediators lipoxins and resolvins and declining docosahexaenoic acid levels in human milk during the first month of lactation

Abstract: The fatty acid mixture of human milk is ideal for the newborn but little is known about its composition in the first few weeks of lactation. Of special interest are the levels of long-chain PUFAs (LCPUFAs), since these are essential for the newborn’s development. Additionally, the LCPUFAs arachidonic acid (AA), eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) are precursors for lipid mediators which regulate inflammation. We determined the composition of 94 human milk samples from 30 mothers over the first month of lactation for fatty acids using GC-MS and quantified lipid mediators using HPLC-MS/MS. Over the four weeks period, DHA levels decreased, while levels of γC18:3 and αC18:3 steadily increased. Intriguingly, we found high concentrations of lipid mediators and their hydroxy fatty acid precursors in human milk, including pro-inflammatory leukotriene B4 (LTB4) and anti-inflammatory and pro-resolving lipoxin A4 (LXA4), resolvin D1 (RvD1) and resolvin E1 (RvE1). Lipid mediator levels were stable with the exception of two direct precursors. Elevated levels of DHA right after birth might represent higher requirements of the newborn and the high content of anti-inflammatory and pro-resolving lipid mediators and their precursors may indicate their role in neonatal immunity and may be one of the reasons for the advantage of human milk over infant formula.

Transfer of Silver Nanoparticles through the Placenta and Breast Milk during in vivo Experiments on Rats.

Abstract: Silver nanoparticles (NPs), widely used in the manufacture of various types of consumer products and for medical applications, belong to novel types of materials that pose potential risks to human health. The potential negative effects of the influence of these NPs on reproduction are insufficiently researched. A quantitative assessment of the transfer of metallic silver nanoparticles through the placenta and breast milk was carried out during an in vivo experiment. We used 34.9 ± 14.8 nm in size silver NPs that were stabilized by low-molecularweight polyvinylpyrrolidone and labeled with the (110m)Ag radioactive isotope using thermal neutron irradiation in a nuclear reactor. [(110m)Ag]-labeled NPs preparations were administered intragastrically via a gavage needle to pregnant (20(th) day of gestation) or lactating (14-16th day of lactation) female rats at a dose of 1.69-2.21 mg/kg of body weight upon conversion into silver. The accumulation of NPs in rat fetuses and infant rats consuming their mother's breast milk was evaluated using a low-background semiconductor gamma-ray spectrometer 24 and 48 hours following labeling, respectively. In all cases, we observed a penetration of the [(110m)Ag]-labeled NPs through the placenta and ther entry into the mother's milk in amounts exceeding by 100-1,000 times the sensitivity of the utilized analytical method. The average level of accumulation of NPs in fetuses was 0.085-0.147% of the administered dose, which was comparable to the accumulation of the label in the liver, blood, and muscle carcass of adult animals and exceeded the penetration of NPs across the hematoencephalic barrier into the brain of females by a factor of 10-100. In lactating females, the total accumulation of [(110m)Ag]-labeled NPs into the milk exceeded 1.94 ± 0.29% of the administered dose over a 48 h period of lactation; not less than 25% of this amount was absorbed into the gastrointestinal tract of infant rats. Thus, this was the first time experimental evidence of the transfer of NPs from mother to offspring through the placenta and breast milk was obtained.

Microbial contamination of human milk purchased via the Internet.

Abstract: OBJECTIVE: To quantify microbial contamination of human milk purchased via the Internet as an indicator of disease risk to recipient infants. METHODS: Cross-sectional sample of human milk purchased via a popular US milk-sharing Web site (2012). Individuals advertising milk were contacted to arrange purchase, and milk was shipped to a rented mailbox in Ohio. The Internet milk samples ( n = 101) were compared with unpasteurized samples of milk donated to a milk bank ( n = 20). RESULTS: Most (74%) Internet milk samples were colonized with Gram-negative bacteria or had >10 4 colony-forming units/mL total aerobic count. They exhibited higher mean total aerobic, total Gram-negative, coliform, and Staphylococcus sp counts than milk bank samples. Growth of most species was positively associated with days in transit (total aerobic count [log 10 colony-forming units/mL] β = 0.71 [95% confidence interval: 0.38–1.05]), and negatively associated with number of months since the milk was expressed (β = −0.36 [95% confidence interval: −0.55 to −0.16]), per simple linear regression. No samples were HIV type 1 RNA-positive; 21% of Internet samples were cytomegalovirus DNA-positive. CONCLUSIONS: Human milk purchased via the Internet exhibited high overall bacterial growth and frequent contamination with pathogenic bacteria, reflecting poor collection, storage, or shipping practices. Infants consuming this milk are at risk for negative outcomes, particularly if born preterm or are medically compromised. Increased use of lactation support services may begin to address the milk supply gap for women who want to feed their child human milk but cannot meet his or her needs.

Effects of high fiber intake during late pregnancy on sow physiology, colostrum production, and piglet performance

Abstract: Dietary fiber given during pregnancy may influence sow endocrinology and increase piglet BW gain during early lactation. The aim of the current study was to determine whether dietary fiber given to sows during late pregnancy induces endocrine changes that could modulate sow colostrum production and, thus, piglet performance. From d 106 of pregnancy until parturition, 29 Landrace×Large White nulliparous sows were fed gestation diets containing 23.4 [high fiber (HF); n=15] or 13.3% total dietary fiber [low fiber (LF); n=14]. In the HF diet, wheat and barley were partly replaced by soybean hulls, wheat bran, sunflower meal (undecorticated), and sugar beet pulp. After parturition, sows were fed a standard lactation diet. Colostrum production was estimated during 24 h, starting at the onset of parturition (T0) and ending at 24 h after parturition (T24) based on piglet weight gains. Jugular blood samples were collected from sows on d 101 of pregnancy, daily from d 111 of gestation to d 3 of lactation, and then on d 7 and 21 of lactation (d 0 being the day of parturition). Postprandial kinetics of plasma glucose and insulin concentrations were determined on d 112 of pregnancy. The feeding treatment did not influence sow colostrum yield (3.9±0.2 kg) or piglet weight gain during the first day postpartum to d 21 of lactation. Colostrum intake of low birth weight piglets (<900 g) was greater in litters from HF sows than from LF sows (216±24 vs. 137±22 g; P=0.02). Preweaning mortality was lower in HF than LF litters (6.2 vs. 14.7%; P=0.01). Circulating concentrations of progesterone, prolactin, estradiol-17β, and cortisol were not influenced by the treatment. Sows fed the HF diet had greater postprandial insulin concentrations than LF sows (P=0.02) whereas the postprandial glucose peak was similar. At T24, colostrum produced by HF sows contained 29% more lipid than colostrum produced by LF sows (P=0.04). Immunoglobulin A concentrations in colostrum were lower at T0 and T24 (P=0.02) in HF than LF sows (at T0: 8.6±1.1 vs. 11.9±1.1 mg/mL; at T24: 2.5±0.7 vs. 4.8±0.7 mg/mL). In conclusion, dietary fiber in late pregnancy affected sow colostrum composition but not colostrum yield, increased colostrum intake of low birth weight piglets, and decreased preweaning mortality, but these effects were not related to changes in peripartum concentrations of the main hormones involved in lactogenesis.

Role of oxytocin signaling in the regulation of body weight

Abstract: Obesity and its associated metabolic disorders are growing health concerns in the US and worldwide. In the US alone, more than two-thirds of the adult population is classified as either overweight or obese [1], highlighting the need to develop new, effective treatments for these conditions. Whereas the hormone oxytocin is well known for its peripheral effects on uterine contraction during parturition and milk ejection during lactation, release of oxytocin from somatodendrites and axonal terminals within the central nervous system (CNS) is implicated in both the formation of prosocial behaviors and in the control of energy balance. Recent findings demonstrate that chronic administration of oxytocin reduces food intake and body weight in diet-induced obese (DIO) and genetically obese rodents with impaired or defective leptin signaling. Importantly, chronic systemic administration of oxytocin out to 6 weeks recapitulates the effects of central administration on body weight loss in DIO rodents at doses that do not result in the development of tolerance. Furthermore, these effects are coupled with induction of Fos (a marker of neuronal activation) in hindbrain areas (e.g. dorsal vagal complex (DVC)) linked to the control of meal size and forebrain areas (e.g. hypothalamus, amygdala) linked to the regulation of food intake and body weight. This review assesses the potential central and peripheral targets by which oxytocin may inhibit body weight gain, its regulation by anorexigenic and orexigenic signals, and its potential use as a therapy that can circumvent leptin resistance and reverse the behavioral and metabolic abnormalities associated with DIO and genetically obese models.

Perinatal manipulation of α-linolenic acid intake induces epigenetic changes in maternal and offspring livers

Abstract: Previous studies indicated that the intake of α-linolenic acid (ALA) can alter the concentration of both ω-6 and ω-3 fatty acids in both mother and offspring, with consequences on postnatal brain development. This study describes the association between maternal ALA availability during gestation and lactation, and alterations in the Fads2 DNA methylation in both maternal and offspring livers, at the end of lactation period. Both Fads2 promoter and intron 1 DNA methylation were increased in the groups receiving postnatal flaxseed oil containing 50% ALA (mothers or pups), while bivariate analysis indicated a significant association of the Fads2 epigenetic status in the liver between each mother and its offspring. In addition, Fads2 expression was negatively correlated with promoter methylation at the individual level in maternal livers (P<0.05). This study also indicated that the interplay between ALA availability during gestation and lactation can differentially alter the expression of desaturases and elongases involved in ω-6 and ω-3 metabolic pathways. In summary, when considering the perinatal dietary ALA requirements in mice, both gestation and lactation periods should be considered as having distinct roles in modulating the metabolism of ω-6 and ω-3 fatty acids in maternal mouse livers.

Effects of a controlled heat stress during late gestation, lactation, and after weaning on thermoregulation, metabolism, and reproduction of primiparous sows.

Abstract: Heat stress (HS) causes seasonal infertility in sows and decreases reproductive efficiency. The objective was to examine thermoregulation, metabolic responses, and reproduction in sows exposed to HS or thermoneutral (TN) conditions during different phases of a production cycle (gestation, lactation, and breeding). Fifty-eight first-parity Landrace (n = 26) or Landrace × Large White F1 (n = 32) sows were rotated through environmental chambers for 57 d beginning in late gestation. The ambient temperature sequences included either TN (18°C to 20°C) or HS (24°C to 30°C) for each production phase with the following treatment groups: TN-TN-TN (n = 15), TN-HS-TN (n = 14), HS-TN-HS (n = 14), and HS-HS-HS (n = 15) for gestation-farrowing-breeding (20, 24, and 13 d, respectively). Regardless of the temperature treatment, rectal temperatures were greater (P < 0.001) during lactation (39.36°C ± 0.01°C) than during the gestation (38.27°C ± 0.01°C) or the breeding period (38.77°C ± 0.01°C). The increase in rectal temperature (P < 0.001) and respiration rate (P < 0.001) in response to the HS was greatest during lactation. There was an effect of day (P < 0.001) on serum IGF-1 and insulin concentrations because both insulin and IGF-1 increased after farrowing. Compared with HS sows, the TN sows had greater feed intake (P < 0.001) and greater serum concentrations of insulin (early lactation; P < 0.05) and IGF-1 (late lactation; P < 0.05) when they were lactating. The effects of HS on sow BW, back fat, and loin eye area were generally not significant. Average BW of individual piglets at weaning was approximately 0.5 kg lighter for the sows in the HS farrowing room (P < 0.05). Weaning-to-estrus interval, percentage sows inseminated after weaning, subsequent farrowing rate, and subsequent total born were not affected by treatment. In summary, regardless of ambient temperature, sows undergo pronounced and sustained changes in rectal temperature when they transition through gestation, lactation, weaning, and rebreeding. The effects of HS on rectal temperature, respiration rate, feed intake, and metabolic hormones were greatest during lactation. The controlled HS that we imposed affected piglet weaning weight, but rebreeding and subsequent farrowing performance were not affected.

Milk oligosaccharide sialyl(α2,3)lactose activates intestinal CD11c+ cells through TLR4

Abstract: Breast milk oligosaccharides shape the intestinal environment by affecting mucosal immunity and bacterial colonization. To clarify the role of milk oligosaccharide sialyl(α2,3)lactose (3SL) in intestinal physiology and disease, we investigated colitis development in Il10(-/-) mice exposed to normal or 3SL-deficient milk during lactation. Onset and progression of intestinal inflammation were delayed in Il10(-/-) mice deficient for the α2,3 sialyltransferase 4 (ST3GAL4) responsible for 3SL biosynthesis. The proinflammatory role of 3SL was confirmed by showing that oral supplementation of newborn Il10(-/-);St3gal4(-/-) mice with 3SL increased colitis severity. Conversely, fostering of newborn Il10(-/-) mice to lactating St3gal4(-/-) mothers reduced colitis severity. 3SL directly stimulated mesenteric lymph node CD11c(+) dendritic cells and induced production of cytokines required for expansion of TH1 and TH17 T cells. The stimulatory effect of 3SL was attenuated in Tlr4-deficient CD11c(+) cells, demonstrating that 3SL induces inflammation through Toll-like receptor 4 (TLR4) signaling. Thus, 3SL directly modulates mucosal immunity, which increases susceptibility to colitis.

Effect of somatic cell count and mastitis pathogens on milk composition in Gyr cows

Abstract: Gyr cows are well adapted to tropical conditions, resistant to some tropical diseases and have satisfactory milk production. However, Gyr dairy herds have a high prevalence of subclinical mastitis, which negatively affects their milk yield and composition. The objectives of this study were (i) to evaluate the effects of seasonality, mammary quarter location (rear x front), mastitis-causing pathogen species, and somatic cell count (SCC) on milk composition in Gyr cows with mammary quarters as the experimental units and (ii) to evaluate the effects of seasonality and somatic cell count (SCC) on milk composition in Gyr cows with cows as the experimental units. A total of 221 lactating Gyr cows from three commercial dairy farms were selected for this study. Individual foremilk quarter samples and composite milk samples were collected once a month over one year from all lactating cows for analysis of SCC, milk composition, and bacteriological culture. Subclinical mastitis reduced lactose, nonfat solids and total solids content, but no difference was found in the protein and fat content between infected and uninfected quarters. Seasonality influenced milk composition both in mammary quarters and composite milk samples. Nevertheless, there was no effect of mammary quarter position on milk composition. Mastitis-causing pathogens affected protein, lactose, nonfat solids, and total solids content, but not milk fat content. Somatic cell count levels affected milk composition in both mammary quarters and composite samples of milk. Intramammary infections in Gyr cows alter milk composition; however, the degree of change depends on the mastitis-causing pathogen. Somatic cell count is negatively associated with reduced lactose and nonfat solids content in milk. Seasonality significantly affects milk composition, in which the concentration of lactose, fat, protein, nonfat solids and total solids differs between dry and wet seasons in Gyr cows.

Carry-Over of Aflatoxin B1 to Aflatoxin M1 in High Yielding Israeli Cows in Mid- and Late-Lactation

Abstract: The potent hepatotoxin and carcinogen aflatoxin B1 (AFB1) is a common mycotoxin contaminant of grains used in animal feeds. Aflatoxin M1 (AFM1) is the major metabolite of AFB1 in mammals, being partially excreted into milk, and is a possible human carcinogen. The maximum permitted concentration of AFM1 in cows' milk is 0.05 μg/kg in Israel and the European Union. Since milk yield and the carry-over of AFB1 in the feed to AFM1 in the milk are highly correlated, it was considered important to determine the AFM1 carry-over in Israeli-Holstein dairy cows, distinguished by world record high milk production. Twelve such cows were used to determine AFM1 carry-over following daily oral administration of feed containing ~86 μg AFB1 for 7 days. The mean carry-over rate at steady-state (Days 3-7) was 5.8% and 2.5% in mid-lactation and late-lactation groups, respectively. The carry-over appears to increase exponentially with milk yield and could be described by the equation: carry-over% = 0.5154 e(0.0521 × milk yield), with r(2) = 0.6224. If these data truly reflect the carry-over in the national Israeli dairy herd, the maximum level of AFB1 in feed should not exceed 1.4 μg/kg, a value 3.6 times lower than the maximum residue level currently applied in Israel.

Lactation Biology Symposium: role of colostrum and colostrum components on glucose metabolism in neonatal calves.

Abstract: In neonatal calves, nutrient intake shifts from continuous glucose supply via the placenta to discontinuous colostrum and milk intake with lactose and fat as main energy sources. Calves are often born hypoglycemic and have to establish endogenous glucose production (eGP) and gluconeogenesis, because lactose intake by colostrum and milk does not meet glucose demands. Besides establishing a passive immunity, colostrum intake stimulates maturation and function of the neonatal gastrointestinal tract (GIT). Nutrients and nonnutritive factors, such as hormones and growth factors, which are present in high amounts in colostrum of first milking after parturition, affect intestinal growth and function and enhance the absorptive capacity of the GIT. Likely as a consequence of that, colostrum feeding improves the glucose status in neonatal calves by increasing glucose absorption, which results in elevated postprandial plasma glucose concentrations. Hepatic glycogen concentrations rise much greater when colostrum instead of a milk-based colostrum replacer (formula with same nutrient composition as colostrum but almost no biologically active substances, such as hormones and growth factors) is fed. In contrast, first-pass glucose uptake in the splanchnic tissue tended to be greater in calves fed formula. The greater plasma glucose rise and improved energy status in neonatal calves after colostrum intake lead to greater insulin secretion and accelerated stimulation of anabolic processes indicated by enhanced maturation of the postnatal somatotropic axis in neonatal calves. Hormones involved in stimulation of eGP, such as glucagon and cortisol, depend on neonatal diet, but their effects on eGP stimulation seem to be impaired. Although colostrum feeding affects systemic insulin, IGF-I, and leptin concentrations, evidence for systemic action of colostral insulin, IGF-I, and leptin in neonatal calves is weak. Studies so far indicate no absorption of insulin, IGF-I, and leptin from colostrum in neonatal calves, unlike in rodents where systemic effects of colostral leptin are demonstrated. Therefore, glucose availability in neonatal calves is promoted by perinatal maturation of eGP and colostrum intake. There may be long-lasting effects of an improved colostrum supply and glucose status on postnatal growth and development, and colostrum supply may contribute to neonatal programming of performance (milk and growth) in later life, but data proving this concept are missing.

MiR-103 controls milk fat accumulation in goat (Capra hircus) mammary gland during lactation.

Abstract: Milk is the primary source of nutrition for young mammals including humans. The nutritional value of milk is mainly attributable to fats and proteins fractions. In comparison to cow milk, goat milk contains greater amounts of total fat, including much higher levels of the beneficial unsaturated fatty acids. MicroRNAs (miRNAs), a well-defined group of small RNAs containing about 22 nucleotides (nt), participate in various metabolic processes across species. However, little is known regarding the role of miRNAs in regulating goat milk composition. In the present study, we performed high-throughput sequencing to identify mammary gland-enriched miRNAs in lactating goats. We identified 30 highly expressed miRNAs in the mammary gland, including miR-103. Further studies revealed that miR-103 expression correlates with the lactation. Further functional analysis showed that over-expression of miR-103 in mammary gland epithelial cells increases transcription of genes associated with milk fat synthesis, resulting in an up-regulation of fat droplet formation, triglyceride accumulation, and the proportion of unsaturated fatty acids. This study provides new insight into the functions of miR-103, as well as the molecular mechanisms that regulate milk fat synthesis.

Compound Heterozygous Mutations in SLC30A2/ZnT2 Results in Low Milk Zinc Concentrations: A Novel Mechanism for Zinc Deficiency in a Breast-Fed Infant

Abstract: Zinc concentrations in breast milk are considerably higher than those of the maternal serum, to meet the infant's requirements for normal growth and development. Thus, effective mechanisms ensuring secretion of large amounts of zinc into the milk operate in mammary epithelial cells during lactation. ZnT2 was recently found to play an essential role in the secretion of zinc into milk. Heterozygous mutations of human ZnT2 (hZnT2), including H54R and G87R, in mothers result in low (>75% reduction) secretion of zinc into the breast milk, and infants fed on the milk develop transient neonatal zinc deficiency. We identified two novel missense mutations in the SLC30A2/ZnT2 gene in a Japanese mother with low milk zinc concentrations (>90% reduction) whose infant developed severe zinc deficiency; a T to C transition (c.454T>C) at exon 4, which substitutes a tryptophan residue with an arginine residue (W152R), and a C to T transition (c.887C>T) at exon 7, which substitutes a serine residue with a leucine residue (S296L). Biochemical characterization using zinc-sensitive DT40 cells indicated that the W152R mutation abolished the abilities to transport zinc and to form a dimer complex, indicating a loss-of-function mutation. The S296L mutation retained both abilities but was extremely destabilized. The two mutations were found on different alleles, indicating that the genotype of the mother with low milk zinc was compound heterozygous. These results show novel compound heterozygous mutations in the SLC30A2/ZnT2 gene causing zinc deficiency in a breast-fed infant.

Plasticity of hypothalamic dopamine neurons during lactation results in dissociation of electrical activity and release.

Abstract: Tuberoinfundibular dopamine (TIDA) neurons are the central regulators of prolactin (PRL) secretion. Their extensive functional plasticity allows a change from low PRL secretion in the non-pregnant state to the condition of hyperprolactinemia that characterizes lactation. To allow this rise in PRL, TIDA neurons are thought to become unresponsive to PRL at lactation and functionally silenced. Here we show that, contrary to expectations, the electrical properties of the system were not modified during lactation and that the neurons remained electrically responsive to a PRL stimulus, with PRL inducing an acute increase in their firing rate during lactation that was identical to that seen in non-pregnant mice. Furthermore, we show a long-term organization of TIDA neuron electrical activity with an harmonization of their firing rates, which remains intact during lactation. However, PRL-induced secretion of dopamine (DA) at the median eminence was strongly blunted during lactation, at least in part attributable to lack of phosphorylation of tyrosine hydroxylase, the key enzyme involved in DA synthesis. We therefore conclude that lactation, rather than involving electrical silencing of TIDA neurons, represents a condition of decoupling between electrical activity at the cell body and DA secretion at the median eminence.

Effects of shortening the dry period of dairy cows on milk production, energy balance, health, and fertility: a systematic review.

Abstract: A dry period of 6-8 weeks for dairy cows is generally thought to maximise milk production in the next lactation. However, the value of such a long dry period is increasingly questioned. In particular, shortening the dry period shifts milk production from the critical period after calving to the weeks before calving. This shift in milk production could improve the energy balance (EB), health and fertility of dairy cows. The objective of this study was to systematically review the current knowledge on dry period length in relation to milk production, EB, fertility, and health of cows and calves. A meta-analysis was performed for variables where at least five studies were available. Overall, both shortening and omitting the dry period reduces milk production, increases milk protein percentage and tends to reduce the risk of ketosis in the next lactation. Individual studies reported an improvement of EB after a short or no dry period, compared with a conventional dry period. Shortening or omitting the dry period did not affect milk fat percentage and shortening the dry period did not alter the odds ratio for mastitis, metritis, or fertility measures in the next lactation. So, current evidence for an improvement of health and fertility of dairy cows is marginal and may be partly explained by the limited number of studies which have evaluated health and fertility in relation to dry period length, the limited number of animals in those studies and the variable responses reported.