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Conference papers

Prolactin-release inhibition and once daily milking affect mammary cell activity at a transcriptional level

Abstract : Inhibiting milking-induced prolactin (PRL) release and reducing milking frequency reduce the quantity of milk produced by dairy cows. Nevertheless, the mechanisms by which these two parameters modulate milk yield are not clear. To assess the regulation of the cell activity, by PRL and milking frequencies, five Holstein cows in early lactation received daily i.m. injection of 1 mg of Quinagolide, a suppressor of PRL release, for 9 weeks. Four control cows received the vehicle (water). During the last week of treatment, one half-gland was milked once and the other twice daily. Mammary biopsies were taken after 4 and 8 weeks of quinagolide treatment and epithelial cells were isolated from milk of both halvesudders in both groups of animals during the differential milking. Epithelial cells were prepared after milk centrifugation and by purification using an anticytoketatin antibody bound to magnetic beads. RNA was extracted from mammary biopsies and milk purified epithelial cells. Milk protein mRNA expression were analysed by quantitative real time reverse transcription PCR. Quinagolide treatment induced a faster decline in milk production (- 5.3 kg/d compared to control during the last 4 weeks of treatments, P <0.05). Differential milking resulted in an important reduction of milk production in the half-gland once daily milked (P < 0.001). In the half gland twice daily milked, the inhibitory effect of quinagolide was maintained (P < 0.05), but was lost in the half-gland once daily milked (P > 0.15). Levels of kappa casein (P<0.05) and alpha lactalbumin (P=0.06) mRNA were lower in mammary biopsies of Quinagolide-treated cows at week 4. Accordingly, the mRNA levels of kappa casein (P<0.05) and alpha lactalbumin (P=0.06) were also lower in milk purified epithelial cells from Quinagolide treated cows during the differential milking. Milking frequency also induced variations in milk protein mRNA levels in milk purified epithelial cells. Levels of kappa casein (P<0.05) and alpha lactalbumin (P<0.01) mRNA were downregulated in once daily milked udders compared to twice daily ones. In conclusion, chronic administration of the prolactin-release inhibitor Quinagolide and once daily milking reduced milk production in dairy cows by affecting mammary cell activity at a transcriptionnal level. Moreover milk purified epithelial cells seem to be a valuable source of cells to study transcriptional regulations in mammary cells.
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Submitted on : Friday, September 7, 2012 - 4:11:18 PM
Last modification on : Wednesday, April 6, 2022 - 4:08:19 PM


  • HAL Id : hal-00730140, version 1


Marion Boutinaud, Vanessa Lollivier, R.M. Bruckmaier, P. Lacasse. Prolactin-release inhibition and once daily milking affect mammary cell activity at a transcriptional level. 6th International Symposium on Milk Genomics & Human Health, Sep 2009, Paris (FR), France. ⟨hal-00730140⟩



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