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Mammary cell activity and turnover in dairy cows treated with the prolactin-release inhibitor quinagolide and milked once daily.
- Source :
-
Journal of Dairy Science . Jan2012, Vol. 95 Issue 1, p177-187. 11p. 2 Charts, 2 Graphs. - Publication Year :
- 2012
-
Abstract
- To assess the regulation of mammary cell activity, survival, and proliferation by prolactin (PRL), 5 Holstein cows in early lactation received daily i.m. injections of 1 mg of quinagolide, a suppressor of PRL release, for 9 wk, whereas 4 control cows received the vehicle (water) only. During the last week of treatment, one udder half was milked once a day (1x) and the other twice a day (2x). Mammary biopsies were harvested 1 wk before and 4 and 8 wk after the start of quinagolide treatment. The quinagolide injections reduced milk yield and resulted in lower levels of κ-casein and a-lactalbumin mRNA in the mammary biopsies at wk 4 compared with the control cows. In the mammary tissue of the quinagolide-treated cows at wk 8 of treatment, cell proliferation (as determined by proliferating cell nuclear antigen labeling) was lower and apoptosis (as determined by the terminal deoxynucleotidyl transferase-mediated dUTP nick-end labeling assay) was higher than in the mammary tissue of the control cows. During differential milking, mammary epithelial cells (MEC) were extracted from the milk by centrifugation and purified by immunocytochemical binding to allow variations in the levels of mammary transcripts to be observed. After 9 wk of treatment, levels of a-lactalbumin and κ-casein mRNA were lower in the MEC isolated from milk of the quinagolide-treated cows. This effect was associated with lower PRL receptor mRNA levels and a tendency toward lower viability in the milk-isolated MEC from the 2x-milked glands. The decrease from 2x milking to 1x milking also downregulated a-lactalbumin and κ-casein transcripts in the milk-isolated MEC. Viability was higher for the MEC collected from the 1x-milked udder halves compared with the 2x-milked halves. In conclusion, the reduction in milk yield after chronic administration of the PRL-release inhibitor quinagolide is associated with a reduction in mammary cell activity, survival, and proliferation in lactating dairy cows. Reduced milking frequency was also associated with a decrease in MEC activity. [ABSTRACT FROM AUTHOR]
- Subjects :
- *PROLACTIN
*HOLSTEIN-Friesian cattle
*LACTATION in cattle
*COWS
*MILK yield
Subjects
Details
- Language :
- English
- ISSN :
- 00220302
- Volume :
- 95
- Issue :
- 1
- Database :
- Academic Search Index
- Journal :
- Journal of Dairy Science
- Publication Type :
- Academic Journal
- Accession number :
- 71040220
- Full Text :
- https://doi.org/10.3168/jds.2011-4461