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Use of milk cells to examine the effect of breeding practises on lactose synthesis at the RNA level in dairy cows.

Abstract : Once daily milking (ODM) and dietary restriction decrease milk yield in dairy cows by cellular mechanisms that remain unclear , especially with regards to the synthesis of lactose, the main osmotic agent of milk. In this study, we proposed to use the mammary epithelial cells (MEC) isolated from milk, as a non invasive method to characterise the transmembrane transport of glucose (the main precursor of lactose) and the synthesis of lactose. Variations in mRNA levels of Glut1, Sgtl1 (transport of glucose) and of a-Lactalbumin and Galactosyltransferase were determined. Five multiparous multiparius Prim’ Holstein cows in their 5-6th lactation month were subjected to a reversal design in which the cows were milked once or twice daily while fed a diet providing 98 or 70% of needs determined before the trial. On day 7 of each experimental week, cells were isolated from fresh milk by centrifugation and MEC were separated from milk cells using magnetic beads associated with an anti Cytokeratin 8 antibody. Total RNA was extracted from MEC using Trizol Reagent and a realtime reverse transcription (RT) –PCR was performed. Data were analysed by Anova. These methods of cells and RNA preparations yielded sufficient RNA of good quality to analyse mRNA quantification by RT – PCR. In this study, ODM provokes significant decrease in milk yield (–5.1 kg/d) associated to a decrease in the mRNA levels of a-Lactalbumin (-68%) and the two glucose transmembrane transporters Glut1 (-24%) and Sglt1 (-48%) with no change in Galactosyltransferase mRNA level. Dietary restriction caused a decrease in milk yield (-2.9 kg/d) associated to a decrease in the glucose transporters mRNA levels (- 55 % for both Glut1 and Sglt1) without any change in a-Lactalbumin and Galactosyltransferase mRNA levels. Theses results show that ODM and dietary restriction act differently on the MEC for the decrease in milk production. Both treatments leads to a decrease in the lactose synthesis (data not shown) involving the decrease in glucose supply probably due to the decrease in the gene transcription of glucose transmembrane transporters. Only ODM seems to act on the activity of the lactose synthase enzyme by the regulation of the co-enzyme a-Lactalbumin at a transcriptional level. Thus, the use of mammary epithelial cells obtained from milk gives interesting and comprehensive results to examine the effect of breeding practises at the transcriptional level of genes involved in milk synthesis in dairy cows.
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https://hal.inrae.fr/hal-02819115
Contributor : Migration Prodinra <>
Submitted on : Saturday, June 6, 2020 - 4:32:05 PM
Last modification on : Friday, April 23, 2021 - 10:44:01 AM

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  • HAL Id : hal-02819115, version 1
  • PRODINRA : 475555

Citation

Mohamed Hedi Ben Chedly, Marion Boutinaud, Jocelyne Guinard-Flament, Eloise Delamaire. Use of milk cells to examine the effect of breeding practises on lactose synthesis at the RNA level in dairy cows.. 3rd Symposium on Milk Genomics and Human Health, 2006, Bruxelles, Belgium. ⟨hal-02819115⟩

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