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Mammary gland transcriptome study in heifers

ABSTRACT: A better understanding of impacts of nutrition during pre- weaning and post- weaning period is needed in order to design feeding strategies that optimize lifetime productivity. Therefore, the objectives of the present study were three-fold: to evaluate nutrition-induced changes of 1) growth from birth to first calving in heifers, 2) its impact on first-lactation milk yield and composition and 3) evaluate nutrition-induced changes in gene expression of mammary gland in Parda de Montaña heifers. Sixteen Parda de Montaña heifers, were randomly but equally assigned at birth to one of four management strategies, in a 2 x 2 factorial experiment. In the pre-weaning period (0-6 months of age), all the heifers suckled their dams twice daily for 30 minutes. Half of the heifers (n=8) were supplemented a starter concentrate (CON) while the other half only had access to their dam’s milk (NOCON). In the post-weaning period (6-15 months), half of the heifers of each pre-weaning feeding treatment received alfalfa hay ad libitum plus concentrates, with a different forage to concentrate ratio (F:C), 67:33 (67F:33C) or 87:13 (87F:13C). Plasma metabolites and hormones concentration at weaning was determined, and cows and their calves weigh was recorded once/week throughout the first lactation, and their ADG was calculated. Milk composition and quantity was determined during the first 4 months of lactation. Mammary tissue samples were taken by biopsy at weaning at the end of first lactation. RNA mammary gland samples (n=16, 8 samples from each treatment) were analyzed by using Bovine Gene 1.1 ST Array Strip. The results of the present study showed that heifers that received concentrate during pre- weaning period had greater BW at weaning when compared to NOCON heifers. Concentrate supplementation during the pre-weaning period increased heifers’ weight gains in the pre-weaning period (P < 0.001) but decreased weight gains in the post-weaning period (P < 0.01) and during pregnancy (P < 0.05). In addition, CON cows had lower milk production throughout the 4 months of the first lactation when compared with NOCON (P < 0.01). Moreover CON cows had decreased milk crude protein, crude fat, lactose, extract and casein content in their first lactation. In addition, cows that received concentrate during pre- weaning period showed greater SCC at the third and fourth month of lactation. Different gene expression patterns were found between CON and NOCON animals. Overall, concentrate supplementation at pre- weaning resulted in up –regulation of genes related with immune response and chemokine activity, suggesting that these animals might be in a compromised immune status, probably being at greater risk to develop mastitis in the later periods.

ORGANISM(S): Bos taurus

PROVIDER: GSE78173 | GEO | 2017/07/12

SECONDARY ACCESSION(S): PRJNA312823

REPOSITORIES: GEO

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Project description:Methods: During the last trimester of the gestation, 12 heifers were immunized using intramuscular injection with heat-killed E. coli P4 emulsified in Montanide ISA 61VG® oil adjuvant (SEPPIC), as recommended by the manufacturer. Two months later, half of the heifers (IM group, n=6) got a second injection as a booster. Others received 50 µg of protein concentrate prepared from E. coli P4 supernate in two quarters (IMM group, n=6). Cows of the control group (CONT, n=6) were injected intramuscularly with adjuvant only at the same dates. Cows were then challenged on average at 49 days in milk in one healthy quarter by infusion of a E. coli P4 bacterial suspension (10e3 bacteria). Blood was collected before experiment, and seven days after the first and the second injection (immunization phase), and then at 0, 12 and 40 hours after infection (challenge phase). Results : Whole blood transcriptome through RNA-seq identifies the main biological functions altered during an E. coli mastitis. Systemic and mammary routes of E. coli immunization elicit different gene expression profiles that correlated with the levels of protection Conclusions: Intramuscular immunization is correlated with a high systemic Th1 response that is not as protective as the local route of immunization. During the last trimester of the gestation, 12 heifers were immunized using intramuscular injection with heat-killed E. coli P4 emulsified in Montanide ISA 61VG® oil adjuvant (SEPPIC), as recommended by the manufacturer. Two months later, half of the heifers (IM group, n=6) got a second injection as a booster. Others received 50 µg of protein concentrate prepared from E. coli P4 supernate in two quarters (IMM group, n=6). Cows of the control group (CONT, n=6) were injected intramuscularly with adjuvant only at the same dates. Cows were then challenged on average at 49 days in milk in one healthy quarter by infusion of a E. coli P4 bacterial suspension (10e3 bacteria). Blood was collected before experiment, and seven days after the first and the second injection (immunization phase), and then at 0, 12 and 40 hours after infection (challenge phase).

Project description:Background: To reduce costs of rearing replacement heifers, researchers have focused on decreasing age at breeding and first calving, and to increase returns upon initiation of lactation the focus has been on increasing mammary development prior to onset of first lactation. Enhanced plane of nutrition pre-weaning may benefit the entire replacement heifer operation by promoting mammary gland development and greater future production. Methods: Twelve Holstein heifer calves (<1 wk old) were reared on 1 of 2 dietary treatments (n = 6/group) for 8 wk: a control group fed a restricted milk replacer at 0.45 kg/d (R, 20% crude protein, 20% fat), or an accelerated group fed an enhanced milk replacer at 1.13 kg/d (EH, 28% crude protein, 25% fat). At weaning (8 wk), calves were euthanized and sub-samples of mammary parenchyma (PAR) and mammary fat pad (MFP) were harvested upon removal from the body. Total RNA from both tissues was extracted and sequenced using the Illumina HiSeq2500 platform. The Dynamic Impact Approach (DIA) and Ingenuity Pathway Analysis (IPA) were used for pathway analysis and functions, gene networks, and cross-talk analyses of the two tissues. Results: When comparing EH vs R 1,561 genes (↑895, and ↓666) and 970 genes (↑506, and ↓464) were found differentially expressed in PAR and MFP, respectively. DIA and IPA results highlight a greater proliferation and differentiation activity in both PAR and MFP, supported by an increased metabolic activity. When calves were fed EH, the PAR displayed transcriptional signs of greater overall organ development, with higher ductal growth and branching, together with a supportive blood vessel and nerve network. These activities were mediated by intracellular cascades, such as AKT, SHH, MAPKs, and Wnt, probably activated by hormones, growth factors, and endogenous molecules. The analysis also revealed strong communication between MFP and PAR, with the first enhancing the development of PAR through secreted growth factors and the recruitment of immune cells. Conclusion: The transcriptomics and bioinformatics approach highlighted the mechanisms that mediate the mammary gland response to a higher plane of nutrition in the pre-weaning period.

Project description:Cows exposed to short day photoperiod (SD, 8L:16D) during the 60-day non-lactating period prior to parturition produce more milk in their subsequent lactation compared to cows exposed to long day photoperiod (LD,16L:8D). Although this response is well-established in dairy cows, the underlying mechanisms are not understood. We hypothesized that differential gene expression in cows exposed to SD or LD photoperiods during the dry period could be used to identify the functional basis for the subsequent increase in milk production during lactation. Pregnant, multiparous cows were maintained on a SD or LD photoperiod for 60-days prior to parturition. Mammary biopsies were obtained on days -24 and -9 relative to parturition and Affymetrix GeneChip® Bovine Genome Arrays were used to quantify gene expression. Sixty-four genes were differentially expressed (p ≤ 0.05 and fold-change ≥ |1.5|) between SD and LD treatments. Many of these genes were associated with cell growth and proliferation, or immune function. Ingenuity Pathway Analysis predicted upstream regulators to include TNF, TGFβ1, interferon γ and several interleukins. In addition, expression of 125 genes was significantly different between day -24 and day -9; those genes were associated with milk component metabolism and immune function. The interaction of photoperiod and time affected 32 genes associated with insulin-like growth factor (IGF-I) signaling. Genes differentially expressed in response to photoperiod were associated with mammary development and immune function consistent with the enhancement of milk yield in the ensuing lactation. Our results provide insight into the mechanisms by which photoperiod affects the mammary gland and subsequently lactation. Data were analyzed for the effect of photoperiod treatment (LD minus SD), time relative to parturition (day -24 minus day -9) and the interaction of photoperiod treatment and time ((LD minus SD day -9) minus (LD minus SD day -24))

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Mammary gland transcriptome study in heifers

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