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Effect of early-life plane of nutrition on the transcriptional profile of the hypothalamus in heifer calves

ABSTRACT: The objective of this study was to examine changes in hypothalamic gene expression of heifer calves offered varying planes of nutrition during early life. Angus X Holstein-Friesian heifer calves (19 ± 5 days of age, BW: 51.2 ± 7.8 kg, mean ± SD) were offered a high (HP, n=14) or moderate plane of nutrition (MP, n=15) from 3 to 21 weeks of age to achieve a target growth rate of 1.2 kg/d and 0.5 kg/d, respectively. At 21 weeks of age, all calves were euthanized and the hypothalamus of each calf recovered. RNA was extracted and hypothalamic gene expression examined using RNAseq. Compared with calves on the moderate plane of nutrition, a HP of nutrition altered the expression of 39 transcripts in the hypothalamus. Biological pathway analysis revealed these differentially expressed genes to be involved in pathways including acute phase response signalling, STAT3 pathway, and tight junction signalling. Additionally, biological functions affected by early life plane of nutrition included cell-to-cell signalling and interaction, molecular transport, small molecule biochemistry, behaviour, nervous system development and function, nucleic acid metabolism, and cellular function and maintenance.

ORGANISM(S): Bos taurus

PROVIDER: GSE153495 | GEO | 2021/07/14

REPOSITORIES: GEO

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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.

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Effect of early-life plane of nutrition on the transcriptional profile of the hypothalamus in heifer calves

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