Expression of Human GCSF in Mammary Gland of Mice by Injection of Plasmid DNA

The vectors carrying the genes coding for the proteins of interest are of unpredictable efficiency in transgenic animals. The expression vector of mammary gland (pINGG) containing GCSF genomic DNA was injected into mouse mammary gland, and expression was detected in the milk of mice. The result showed that mammary gland injection method could provide a convenient transient system to confirm vector validity.

The Effect of Administration of Rutin on Plasma Levels of Estrogen, Prolactin, Growth Hormone and Gene Expression of Their Receptors in Mammary Glands in Ovariectomized Rats

The development of mammary glands, endocrine hormone concentrations and the gene expression of related receptors were measured in ovariectomized virgin rats after adminstration of an estrogen-like plant extract, rutin. Thirty-two ovariectomized virgin Wistar rats were randomly assigned to 4 treatments with 8 animals each： gastric infusion of 2 mL normal saline per unovariectomized rat per day （Sham）, gastric infusion of 2 mL normal saline per ovariectomized rat per day （Ova）, gastric infusion of 60 mg rutin kg-1 body weight （BW） per ovariectomized rat per day （Ova＋Rut）, or intramuscular injection of 60 ug estradiol kg-1 BW per ovariectomized rat weekly （Ova＋Est）. Samples of blood and mammary glands were harvested to determine the levels of estrogen （E2）, prolactin （PRL） and growth hormone （GH）, and the gene expression of estrogen receptors （ER）, prolactin receptors （PRLR） and growth hormone receptors （GHR） with radioimmunoassy （RIA） and RT-PCR technology, respectively. The E2 concentration in plasma and gland tissues from the rats of Ovx＋Rut or Ovx＋Est was higher than that of Ovx （P〈0.05）, but the plasma E2 concentration from the rats of Ovx＋Rut was lower than that of Sham （P〈0.05）. The order of the PRL concentration in plasma and gland tissues was Ovx〈Ovx＋Rut〈Ovx＋Est 〈Sham, and the difference in each treatment （P〈0.05）. The plasma GH concentration was lower in Ovx than in Ovx＋Rut or Ovx＋Est, and lower in Ovx＋Rut than in Sham （P〈0.05）. The GH concentration in gland tissues was lower in Ovx than in Ovx＋Rut or Ovx＋Est （P〈0.05）, and lower in Ovx＋Rut than in Sham （P〈0.05）. The gene expression of ER in gland tissues was increased in an order as Ovx〈Ovx＋Rut〈Ovx＋Est〈Sham （P〈0.05）, and PRLR, GHR showed the same trend. In conclusion, adminstration of rutin increased the E2 concentration in plasma and mammary glands, promoted pituitary PRL and GH release, up-regulated the gene expression of ER, PRLR and GHR, and stimulated mammary development in ovariectomized virgin rats.

A cell transcriptomic profile p ovides insights into adipocytes of porcine mammary gland across development

Background Studying the composition and developmental mechanisms in mammary gland is crucial for healthy growth of newborns. The mammary gland is inherently heterogeneous, and its physiological function dependents on the gene expression of multiple cell types. Most studies focused on epithelial cells, disregarding the role of neighboring adipocytes.Results Here, we constructed the largest transcriptomic dataset of porcine mammary gland cells thus far. The dataset captured 126,829 high-quality nuclei from physiological mammary glands across five developmental stages(d 90 of gestation, G90;d 0 after lactation, L0;d 20 after lactation, L20;2 d post natural involution, PI2;7 d post natural involution, PI7). Seven cell types were identified, including epithelial cells, adipocytes, endothelial cells, fibroblasts cells, immune cells, myoepithelial cells and precursor cells. Our data indicate that mammary glands at different developmental stages have distinct phenotypic and transcriptional signatures. During late gestation(G90), the differentiation and proliferation of adipocytes were inhibited. Meanwhile, partly epithelial cells were completely differentiated. Pseudo-time analysis showed that epithelial cells undergo three stages to achieve lactation, including cellular differentiation, hormone sensing, and metabolic activation. During lactation(L0 and L20), adipocytes area accounts for less than 0.5% of mammary glands. To maintain their own survival, the adipocyte exhibited a poorly differentiated state and a proliferative capacity. Epithelial cells initiate lactation upon hormonal stimulation. After fulfilling lactation mission, their undergo physiological death under high intensity lactation. Interestingly, the physiological dead cells seem to be actively cleared by immune cells via CCL21-ACKR4 pathway. This biological process may be an important mechanism for maintaining homeostasis of the mammary gland. During natural involution(PI2 and PI7), epithelial cell populations dedifferentiate into mesenchymal stem cells to maintain the lactation potential of mammary glands for the next lactation cycle.Conclusion The molecular mechanisms of dedifferentiation, proliferation and redifferentiation of adipocytes and epithelial cells were revealed from late pregnancy to natural involution. This cell transcriptomic profile constitutes an essential reference for future studies in the development and remodeling of the mammary gland at different stages.

Matrix metalloproteinases and their expression in mammary gland

The matrix metalloproteinases (MMPs) are a family of zinc-dependent endopeptidases that play a key role in both normal and pathological processes involving tissue remodeling events. The expression of these proteolytic enzymes is highly regulated by a balance between extracellular matrix (ECM) deposition and its degradation, and is controlled by growth factors, cytokines, hormones, as well as interactions with the ECM macromolecules. Furthermore, the activity of the MMPs is regulated by their natural endogenous inhibitors, which are members of the tissue inhibitor of metalloproteinases (TIMP) family. In the normal mammary gland, MMPs are expressed during ductal development, lobulo-alveolar development in pregnancy and involution after lactation. Under pathological conditions, such as tumorigenesis, the dysregulated expression of MMPs play a role in tumor initiation, progression and malignant conversion as well as facilitating invasion and motastasis of malignant cells through degradation of the ECM and basement membranes. Matrix metalloproteinases and their expression in mammary gland

The Expression of the IGF Family During Mouse Mammary Gland Development

This study was to determine the patterns and levels of IGF family members＇ expression during postnatal mammary gland development. The authors investigated the protein expression profile of the major components of the IGF axis in murine mammary glands. All the proteins examined, IGF- Ⅰ, IGF- Ⅱ, and IGF- Ⅰ receptor （IGF-Ⅰ R） were expressed at greatly different levels and displayed unique expression profiles. IGF- Ⅱ and IGF- ⅠR were always expressed at significantly higher levels than IGF- Ⅰ. IGF- Ⅰwas localized in adipocytes as well as the epithelial and stromal compartments, but just distinctly expressed where mammary cells aggregated to form ducts, in virgins. The IGF- Ⅱ was localized only on the basal layer epithelial cell membranes of ducts and alveoli, with a peak level on the initiation of lactation. The higher level of IGF- ⅠR compared with IGF- Ⅰ was also found in adipocytes as well as in the epithelial and stromal compartments, especially during pregnancy and late lactation. The IGF- Ⅰ R pathway was obviously significant for the development of the mammary parenchyma and stroma. Overall, the comparison of the expression profiles of these different proteins would strongly suggest that they were likely to have different functions throughout the mammary gland development, and it also highlighted the potential interactions and coregulation of the members of this axis. It seems that IGF- Ⅱ was the major local modulator rather than IGF- Ⅰ by an IGF- Ⅰ R-independent pathway, especially for initiation of lactation. This study has demonstrated the importance and complexity of the IGF axis during mammary gland development and provides a valuable resource for future research in this area.

Induced in vitro Expression of Human Lactoferrin in Goat Mammary Gland Epithelial Cell

[Objective]The aim of this study was to explore the technical system of induced expression in vitro of goat mammary gland epithelial cell,and evaluate expression efficiency of mammary gland specific vector and foreign protein at the cell level.[Method]Goat mammary gland epithelial cell transfected by human lactoferrin gene was inducted by culturing in DMEM/F12 medium supplemented with 5 mg/L insulin,5 mg/L prolactin and 1 mg/L hydrocortisone.Supernatant was collected per 6 hours and concentrated.Expression situation of foreign protein were detected by SDS-PAGE and Western blotting.[Result]There was target protein expression in the induced culture medium,which molecular weight was about 42 kD.[Conclusion]The method used in this study can induce goat mammary gland epithelial cell to express foreign gene,it lays a foundation for researching heterologous expression of foreign gene and producing mammary gland bioreactor.

Construction of Antibacterial Peptide CecropinB Eukaryotic Recombinant Vector and Its Expression in Dairy Goat Mammary Gland Epithelial Cells

To investigate the expression of antibacterial peptide CecropinB cDNA in dairy goat mammary gland epithelial cells,the CecropinB gene was cloned and was inserted into a eukaryotic vector pECFP-C1 to construct the recombinant plasmid pECFP-B by genetic engineering technique.Recombinant plasmid pECFP-B was transfected into dairy goat mammary gland epithelial to detect the bactericidal activity of CecropinB.The expression of CecropinB was also detected.The result of RT-PCR demonstrated CecropinB gene was expressed in transfected cells.CecropinB recombinant plasmid DNA was injected into udders and CecropinB was expressed in mammary gland,exhibiting bactericidal activity to Staphylococcus aureus in vivo experiments.

Comparative Expression Profiling of Lactogenic Hormone Receptor and It’s Signaling Molecules of Bovine Mammary Glands during lactation

Milk synthesis is known to be modulated by peptide hormones such as prolactin (PRL), growth hormone (GH), and insulin-like growth factor I (IGF-I). Previous studies suggested that PRL and IGF-I acted directly on mammary epithelial cells and were involved in lactation. Meanwhile, GH is thought to be indirectly involved in lactation by stimulating the secretion of IGF-I. It is controversial as growth hormone receptors (GHR) is expressed in the mammary epithelial cells. In order to clarify whether GH acted directly on mammary gland tissue, we investigated the prolactin receptors (PRLR), IGF-I receptors (IGF-IR), and GHR as well as the gene expression levels of the downstream signaling molecule for each receptor in the mammary gland tissue of Holstein cows during different stages of lactation. The results revealed that the mRNA expressions of PRLR and IGF-IR were highest during early lactation, and the mRNA expression of the GHR was highest during mid-lactation. We also found that the expression profiling of the signal transducer and activator of transcription 5 (STAT5) genes was similar to that of the GHR gene. On the other hand, the expression profiling of the PRLR gene was similar to that of the SHP2 gene. These results suggest that GH acts on the mammary glands directly, milk synthesis and secretion are chiefly stimulated in mid-lactation, and the timing of the action is different for PRL and IGF-I.

Stable Expression of Antibacterial Peptide CecropinB in Dairy Goat Mammary Gland Epithelial Cells

The paper aimed at constructing the eukaryotic expression vector of CecropinB and transfecting it into the goat mammary epithelial cell line. The recombinant plasmid inserted with CecropinB was transfected into the goat mammary epithelial cell by liposome Tfx^M-20. By screening with G418, the stable transfected goat mammary epithelial cell line was established and the transcription and expression of CecropinB were identified by RT-PCR and agarose diffusion experiment, respectively. Results showed that eukaryotic expression vector pECFP-B was constructed successfully. Stable transfected goat mammary epithelial cell line was established and the CecropinB protein was expressed successfully. It provides the solid foundation for further experimental studies on the function of CecropinB.

Differential Expression of Glu-Tubulin in Basal-Like Phenotype Carcinoma of the Mammary Gland

High levels of tubulin expression have been described in a variety of human malignant tumors, and glu-tubulin, in which the C-terminal tyrosine of α-tubulin is removed by tubulin carboxypeptidase. Over-expression has been reported in the malignant tumors of the mammary gland and correlated with poor prognosis immunohistochemically. Furthermore, Nielsen et al. proposed that the use of a panel of four markers (ER, HER 2, CK 5/6, and EGFR) could accurately identify basal-like phenotype carcinoma (BPC) with widely available standard pathologic tools. In our study, major prognostic factors such as patient age, tumor size, histological grade, axillary lymph node metastasis, vessel invasion, and local recurrence in BPC were not significantly different from non BP carcinoma (NBPC). However, the BPC group showed a higher ratio of distant metastasis than that of the NBPC group. In triple-negative carcinoma (TNC) cases, staining for glu-tubulin was observed in 46 cases (63.8%), which consisted of 42 of the 58 BPC patients (72.4%) and 4 of the 14 NBPC patients (28.6%). A significant association was found between the expression of glu-tubulin and BPC, but not NBPC. It seems that our findings also agree with the observation that BPC exhibits aggressive biological behavior and increases the content of glu-tubulin, which plays a greater role in migration and invasion.

The Effects of Amino Acid Nutritional Deficiency on the Expression of Protein Metabolism-Related Genes in the Mammary Gland and Muscle Tissues of Lactating Mice

The mammary gland tissue exhibits a series of responses that are different from those of muscle and other peripheral tissues under amino acid deficiency. So, this present study was designed to investigate the effects of amino acid nutritional deficiency on the expression of protein metabolism-related genes in the mammary gland and muscle tissues of lactating mice. A total of 60 postpartum, lactating Kunming white mice were selected and randomly divided into 5 groups;each group contained 12 mice. Group A was the control group. The mice in group A were maintained on a normal diet after the initiation of lactation. Group B (starved) was given normal saline via intragastric administration. Group C (energy) was given glucose solution via intragastric administration. Groups D and E received a sodium caseinate solution via intragastric administration, which provided 0.5 g protein/d and 1.5 g protein/d, respectively. The results showed the following. 1) When the mice were exposed to nutritional stress caused by dietary amino acid deficiency, the β-casein mRNA expression level was increased in the mammary gland tissue. The increase in β-casein expression was the most significant in the energy-supplemented group, followed by the starved group (P P 14k and C2 (P P P < 0.05). 5) The phosphorylation level of p70S6K was elevated in the muscle tissues collected from the treatment groups. However, the magnitude of the increase was far smaller compared to that in the mammary gland tissues.

Construction and Identification of Mammary Gland-specific Expression Vector of Bovine Tracheal Antimicrobial Peptide (TAP)

[ Objective] This study aimed to construct nmnmm_ry gland-specific expression vector of bovine tracheal antimicrobial peptide （TAP） gene. [ Method] TAP gene of dairy cattle was amplified from the mammary gland tissue by RT-PCR using a pair of primers which were designed according to bovine TAP cDNA se- quence （NM_174776） in GenBank, and then cloned into pMD19-T Simple vector for sequencing. The recombinant plasmid was digested using EcoRI and KpnI, the target gene fragment was recovered and inserted into general mammary gland-specific expression vector pBLG-EGFP harboring enhanced green fluorescent protein （ EGFP）, and transfected into bovine mammary epithelial cells （bMEC）, COS-7 cells and lactating rabbit mmmnary gland tissue by lipofectin transfection. The ex- pression of green fluorescent protein in transfected cells was detected under fluorescence microscopy, and the expression of TAP mRNA in rabbit mammary gland tis- sue was detected by semi-quantity RT-PCR. [ Result] The constructed mammary gland-specific expression vector pBLG-EGFP-TAP specifically expressed EGFP in transfected bMECs. In addition, semi-quantitative RT-PCR result showed that the expression level of TAP mRNA in rabbit mammary gland tissue was significantly enhanced after transfeeted with pBLG-EGFP-TAP. [ Conclusion] The mammary gland-specific expression vector pBLG-EGFP-TAP was successfully constructed, which provided important materials for further investigation of expression characteristics of TAP gene and prevention of bovine mastitis by using genetic engineering technology.

Identification of Differentially Expressed MicroRNAs During the Development of Chinese Murine Mammary Gland

MicroRNAs （miRNAs） are endogenous -22 nucleofide-long noncoding RNAs. In this study, to investigate miRNA expression profiles and their functions in mammary gland development, we have used microarray as well as qRT-PCR, to analyze the miRNA expression changes along the murine mammary cycle during pregnancy, particularly on transition from pregnancy to lactation. It shows that every developmental stage of the mammary gland has its own mjRNA expression pattern. Compared with virgin and involution, some miRNAs such as miR-138 and miR-431 are downregulated, whereas, some miRNAs such as miR-133 and miR-133a-133b are upregulated during pregnancy and lactation. These results indicate that miRNAs are functionally involved in mammary gland development.

Amino acids and mammary gland development:nutritional implications for milk production and neonatal growth

Milk is synthesized by mammary epithelial cells of lactating mammals. The synthetic capacity of the mammary gland depends largely on the number and efficiency of functional mammary epithelial cells. Structural development of the mammary gland occurs during fetal growth, prepubertal and post-pubertal periods, pregnancy, and lactation under the control of various hormones （particularly estrogen, growth hormone, insulin-like growth factor-I, progesterone, placental lactogen, and prolactin） in a species- and stage-dependent manner. Milk is essential for the growth, development, and health of neonates. Amino acids （AA）, present in both free and peptide-bound forms, are the most abundant organic nutrients in the milk of farm animals. Uptake of AA from the arterial blood of the lactating dam is the ultimate source of proteins （primarily 13-casein and a-lactalbumin） and bioactive nitrogenous metabolites in milk. Results of recent studies indicate extensive catabolism of branched-chain AA （leucine, isoleucine and valine） and arginine to synthesize glutamate, glutamine, alanine, aspartate, asparagine, proline, and polyamines. The formation of polypeptides from AA is regulated not only by hormones （e.g., prolactin, insulin and glucocorticoids） and the rate of blood flow across the lactating mammary gland, but also by concentrations of AA, lipids, glucose, vitamins and minerals in the maternal plasma, as well as the activation of the mechanistic （mammalian） target rapamycin signaling by certain AA （e.g., arginine, branched-chain AA, and glutamine）. Knowledge of AA utilization （including metabolism） by mammary epithelial cells will enhance our fundamental understanding of lactation biology and has important implications for improving the efficiency of livestock production worldwide.

Influence on Cellular Signal Transduction Pathway in Dairy Cow Mammary Gland Epithelial Cells by Galactopoietic Compound Isolated from Vaccariae segetalis

The galactopoietic mechanism of Vaccaria segetalis is still unknown. Understanding dibutyl phthalate （DBP） separated from Vaccaria segetalis on the expression of lactation signal transduction genes of mammary gland epithelial cells, including prlr, erα, akt1, socs2, pparγ and elf5, will be helpful to reveal the molecular mechanism. Western blot and qRT- PCR were used to study the change of prlr, erα, akt, socs2, pparγ, and elf5 expression at mRNA and protein level. Co- localization expression of prolactin receptor （PRLR） and estrogen receptor α （ERα） was observed by immunofluorescence; the expression changes of miRNAs （21, 125b, 143, and 195） and the secretion of β-casein and lactose were detected by qRT-PCR and RP-HPLC. The results showed that Vaccaria segetalis active compound had similar fuctions as estrogen and/or prolactin （PRL） in dairy cow mammary gland epithelial cells （DCMECs）, increased the expressions of prlr, erα, akt1, and elf5 genes, while repressed pparγ expressions. DBP promoted socs2 mRNA expression, but its protein expressions were repressed. Furthermore, both DBP and PRL could repress the expressions of miRNA-125b, miRNA-143 and miRNA- 195 in DCMECs. DBP could repress the expression of miRNA-21, while the influence of PRL on miRNA-21 was not certain. DBP could promote the lactation ability of DCMECs by regulating the ER and PRLR cellular signal transduction pathway.

Milk production and composition and metabolic alterations in the mammary gland of heat-stressed lactating dairy cows

This experiment was conducted to investigate the effects of heat stress(HS) on the feed intake, milk production and composition and metabolic alterations in the mammary gland of dairy cows. Twenty Holstein cows were randomly assigned to one of two treatments according to a completely randomized design. Half of the cows were allocated to the HS group in August(summer season), and the other half were assigned to the HS-free group in November(autumn season). HS reduced(P<0.01) dry matter intake(DMI), milk yield, milk protein and milk urea nitrogen(MUN) of cows compared with HSfree control, but increased(P<0.01) milk somatic cell counts(SCC). We determined the HS-induced metabolic alterations and the relevant mechanisms in dairy cows using liquid chromatography mass spectrometry combined with multivariate analyses. Thirty-four metabolites were identified as potential biomarkers for the diagnosis of HS in dairy cows. Ten of these metabolites, glucose, lactate, pyruvate, lactose, β-hydroxybutyrate, citric acid, α-ketoglutarate, urea, creatine, and orotic acid, had high sensitivity and specificity for HS diagnoses, and seven metabolites were also identified as potential biomarkers of HS in plasma, milk, and liver. These substances are involved in glycolysis, lactose, ketone, tricarboxylic acid(TCA), amino acid and nucleotide metabolism, indicating that HS mainly affects lactose, energy and nucleotide metabolism in the mammary gland of lactating dairy cows. This study suggested that HS might affect milk production and composition by affecting the feed intake and substance metabolisms in the mammary gland tissue of lactating dairy cows.

Metabolic Regulation of Mammary Gland Epithelial Cells of Dairy Cow by Galactopoietic Compound Isolated from Vaccariae segetalis

In previous experiment, we isolated a compound dibutyl phthalate （DBP） from Vaccaria segetalis which had galactopoietic function on mammary gland epithelial cells of dairy cow （DCMECs）. In this experiment, we ascertained the metabolic regulation function of DBP on DCMECs. Many genes related to lactation including Stat5, AMPK, b-casein, Glut1, SREBP-1, PEPCK, and ACC were detected by real-time PCR. Furthermore, Stat5 and AMPK were detected by Western blot and immunofluorescence co-localization, respectively. The results showed that DBP stimulates the expression of Stat5 and p-Stat5, thus activates Stat5 cell signal transduction pathway and stimulates b-casein synthesis. DBP also raises the activities of Glut1 and AMPK to stimulate glucose uptake and glycometabolism and activates the expression of AMPK downstream target genes PEPCK and ACC and expression of SREBP-1 to stimulate milk fat synthesis. In addition, the activities of HK, G-6-PDH, ICDH, ATPase, and energy charges were stimulated by DBP to increase the energy metabolism level of DCMECs. The results showed DBP stimulates energy metabolism related to galactopoietic function in DCMECs.

Recent progress of porcine milk components and mammary gland function

As the only nutritional source for newborn piglets,porcine colostrum and milk contain critical nutritional and immunological components including carbohydrates,lipids,and proteins(immunoglobulins).However,porcine milk composition is more complex than these three components.Recently,scientists identified additional and novel components of sow colostrum and milk,including exosomes,oligosaccharides,and bacteria,which possibly act as biological signals and modulate the intestinal environment and immune status in piglets and later in life.Evaluation of these nutritional and non-nutritional components in porcine milk will help better understand the nutritional and biological function of porcine colostrum and milk.Furthermore,some important functions of the porcine mammary gland have been reported in recent published literature.These preliminary studies hypothesized how glucose,amino acids,and fatty acids are transported from maternal blood to the porcine mammary gland for milk synthesis.Therefore,we summarized recent reports on sow milk composition and porcine mammary gland function in this review,with particular emphasis on macronutrient transfer and synthesis mechanisms,which might offer a possible approach for regulation of milk synthesis in the future.

Mammary gland growth and vascularity at parturition and during lactation in primiparous ewes fed differing levels of selenium and nutritional plane during gestation

Background： Objectives were to examine the effects of selenium （Se） supply and maternal nutritional plane during gestation on mammary gland growth, cellular proliferation, and vascularity at parturition and d 20 of lactation. Rambouillet primiparous ewes （n = 84） were allocated to treatments in a 2 x 3 factorial. Factors were dietary Se （adequate Se [ASe, 11.5 μg/kg BW] or high Se [HSe, 77.0 μg/kg BVV]） and nutritional plane （60% IRES], 100% [CON], or 140% [EXC]）. At parturition, lambs were removed and 42 ewes （7/treatment） were necropsied. Remaining ewes were fed a common diet meeting requirements for lactation and mechanically milked twice daily until necropsy on d 20. At both necropsy periods, mammary glands were dissected and tissues harvested. Samples were analyzed for RNA, DNA, and protein content, cell proliferation, and vascularity. Where interactions were present （P 〈 0.05）, least squares means from the highest-order interaction are presented. Results： Final body weight of ewes was least （P 〈 0.002） in RES, intermediate for CON, and greatest for EXC, regardless of stage of the ewe at necropsy （parturition or d 20 of lactation）. In ewes necropsied at parturition, mammary glands were heavier （P = 0.02） in EXC compared to RES, with CON intermediate. Concentration of RNA （rag/g） was decreased （P= 0.01） in EXC compared to CON at parturition. There was a tendency （P= 0.07） for a Se by nutrition interaction in percentage of cells proliferating where ASe-EXC ewes had greater （P_〈 0.02） number of proliferating cells then all other treatments. Mammary vascular area tended （P = 0.08） to be affected by a Se by nutrition interaction where ASe-CON had less （P= 0.007） vascular area than HSe-CON ewes. In ewes necropsied at d 20 of lactation, the number of alveoli per area was decreased （P 〈- 0.05） in RES compared to CON and EXC-fed ewes. Conclusions： Results of this study indicate that proper maternal nutritional plane during gestation is important for mammary gland development, even out to d 20 of lactation.

Effects of dietary valine supplementation during late gestation on the reproductive performance and mammary gland development of gilts

Background:Mammary gland development during late gestation in gilts is a major factor that alters the composition of colostrum and growth performance of piglets.Plasma valine is taken up and metabolized extensively by the mammary gland;however,the effects of valine on mammary gland development during late gestation are still unclear.Thirty primiparous gilts were divided into three treatment groups(n=10)and received one of the three diets starting on day 75 of gestation until the day of farrowing.The total dietary valine to lysine ratio of the three diets was 0.63(LV),0.73(MV),and 0.93(HV),respectively.Results:Dietary valine supplementation during late gestation did not affect(P>0.05)the litter size and weight at farrowing;however,the piglet weight and average daily gain at weaning were linearly increased(P<0.05)as the dietary valine increased.The highest piglet weight at weaning was observed when the gilts were provided the HV diet.Dietary valine supplementation linearly elevated(P<0.05)protein,fat and solids-not-fat and some free amino acids content in colostrum.The concentration of prolactin in plasma of gilts was linearly increased in response to valine supplementation at days 1 and 10 of lactation(P<0.05).Furthermore,with increasing dietary valine allowance,a linear increase(P<0.05)was observed in the area of the lumen of alveolus and the content of DNA,RNA,and total protein in the mammary tissues at day 1 of lactation.Moreover,the protein expression of cyclin D1,p-mTOR,p-S6,and p-4EBP1 was also linearly increased(P<0.05)in the mammary tissue at day 1 of lactation.However,no difference(P>0.05)was observed in the indices related to mammary development and the mTOR signaling pathway at day 21 of lactation.Conclusion:The results revealed that increasing the total dietary valine to lysine ratio to 0.93 during late gestation significantly enhances the piglet weight and average daily gain at weaning probably due to improved development of mammary gland.