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:We evaluated if a higher plane of maternal nutrition during late gestation and weaning age alters the offspringM-bM-^@M-^Ys Longissimus muscle (LM) transcriptome. A microarray analysis was performed in LM samples of early (EW) and normal weaned (NW) Angus M-CM-^W Simmental calves born from cows that were grazing endophyte-infected tall fescue/red clover pastures with no supplement (low plane of nutrition (LPN)), or supplemented with 2.3 kg of dried distillerM-bM-^@M-^Ys grains with solubles and soyhulls (70% DDGS/30% soyhulls) (medium plane of nutrition (MPN)) during the last 90 days of gestation. Biopsies were harvested at 78, 187 and 354 days of age. Bioinformatics analysis highlighted that offspring transcriptome did not respond markedly to cow plane of nutrition, resulting in only 13 differentially expressed genes. However, weaning age and a high-starch diet strongly impacted the transcriptome, especially the immediate activation of the lipogenic program in EW steers. In addition, between 78 and 187 days of age, these animals had an activation of the innate immune system due presumably to macrophage infiltration in intramuscular fat. Between 187 and 354 days of age (i.e. the fattening phase), NW steers had an activation of the lipogenic transcriptome machinery, while EW steers had a clear gene transcription inhibition. The latter appears to have occurred through the epigenetic control of histone acetylases, which were down-regulated. Higher cow plane of nutrition alone affected 35 genes in the LM of steers that underscore the presence of a mechanism of macrophage infiltration likely originating from localized oxidative stress as a result of increased levels of hypoplasia and hypertrophy in LM. A subset of 20 Angus x Simmental beef cows from the University of Illinois Dixon Springs Agriculture Center (DSAC) in Simpson, IL, were selected from a group of animals utilized in a parallel study75. Main effects evaluated were maternal plane of nutrition during late gestation and postnatal management of the offspring. Three months prior to the projected parturition date cows were assigned to treatments (low or medium plane of nutrition) in a split-plot design. Low plane of nutrition (LPN) was achieved by grazing endophyte-infected tall fescue/red clover pastures during July, August, and September with no supplement. Medium plane of nutrition cow diet (MPN) was achieved by grazing endophyte-infected tall fescue/red clover pastures supplemented with 2.3 kg of dried distillerM-bM-^@M-^Ys grains with solubles and soyhulls (70% DDGS/30% soyhulls). Angus x Simmental steer calves were randomly assigned to early or normal weaning treatments within each gestational treatment. This allowed for 10 animals for each postnatal treatment and 5 animals of each of the interactions of gestational M-CM-^W postnatal treatments. At 78 M-BM-1 2 days postpartum, early-wean offspring were weaned, transported to Urbana Beef Unit, and adapted to a high-starch diet until they had ad libitum consumption. At 187 M-BM-1 2 days postpartum, normal-wean offspring were weaned and transported to Urbana Beef Unit. All offspring were co-mingled among treatments. LM biopsies were sampled from a subset of 5 animals per gestational M-CM-^W postnatal treatment at time of early weaning (~78 days) and at time of normal weaning (~187 days), and during the last week prior to harvest (~ 354 days). After normal weaning, all offspring were placed on a common, corn grain-based high-starch finishing diet that is typical of industry management (CP% = 18.1, NDF% = 25.3, ADF% = 14.3, crude fat % = 5.1). All the offspring in the study were harvested at a commercial packing plant when they reached the selected end point target back fat thickness of 1.1 cm. Reported final body weight (BW) was calculated from hot carcass weight using a 62% dressing percentage. In the present study, we used a transcriptome-wide bovine microarray (Agilent-015354 Bovine Oligo Microarray-4x44K) that contains 21,475 unique genes and transcripts of Bos Taurus, with two probes per gene. The methods used for hybridization and scanning were according to manufacturerM-bM-^@M-^Ys protocols and Loor et al45. The microarray data were deposited in the National Center for Biotechnology Information (NCBI) Gene Expression Omnibus (GEO) database (http://www.ncbi.nlm.nih.gov/gds) with accession number GSE-XXXX. GeneSpring GX (Agilent Technologies) was used for data visualization and preliminary data mining. Subsequently, the entire microarray data set with associated statistical P-values were imported into Ingenuity Pathways Analysis M-BM-. (IPA, www.ingenuity.com) in order to examine the number of activated and inhibited differentially expressed genes (DEG). Entrez Gene IDs were used to identify individual sequences. Data from the microarray analysis were normalized for dye and microarray effects (i.e., Lowess normalization and array centering) and used for statistical analysis. The MIXED procedure of SAS (SAS Institute, Inc., Cary, NC, USA) was used for statistical analysis. Fixed effects were treatment (early weaning, normal weaning), diet (low and medium cow plane of nutrition), time (78, 187, and 354 days of age), first, second and third order interactions between diet, time and treatment, and dye (Cy3, Cy5) and random effects included steer and microarray. Raw P values were adjusted using Benjamini and HochbergM-bM-^@M-^Ys false discovery rate (FDR). Bioinformatics analysis of microarray data was performed using DIA 10 and information from the freely-available online databases Kyoto Encyclopedia of Genes and Genomes (KEGG) and Database for Annotation, Visualization, and Integrated Discovery (DAVID) v6.7 databases. A list of gene identifiers (Entrez Gene IDs) was uploaded all at once to extract and summarize functional annotations associated with groups of genes or with each individual gene. The significance value associated with biological processes and pathways is a measure of the likelihood that the distribution of DEG in these pathways and biological processes is due to chance. The significance is expressed as a P-value, which is calculated using the right-tailed Fisher's Exact Test and adjusted using FDR. Details of the DIA approach and its validation have been reported previously. The interpretation of the bioinformatics analysis was performed following the same approach as our previous study.

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Bos taurus

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