Submitted to: Joint Abstracts of the American Dairy Science and Society of Animal Science
Publication Type: Abstract Only
Publication Acceptance Date: 2/20/2005
Publication Date: 7/1/2005
Citation: Annen, E.L., Gentry, P.C., Sprissler, R., Hadsell, D.L., Capuco, A.V., Collier, R.J. 2005. Efffects of continuous milking (cm)and bovine somatotropin(bst) on mammary gene expression in primiparous cows [abstract]. J. Dairy Science. 83(1):364-365. Interpretive Summary:
Technical Abstract: Primiparous cows (n=8) were used in a half udder model in which one half was dry 60 d (CTL) and the other half was CM. Cows were assigned to + (n=4) or ' bST (n=4) treatment. Tissue was sampled at 20 and 8 d prepartum (PP) and 1, 7, and 20 d postpartum (PT). Mammary epithelial cell (MEC) proliferation was increased PP compared to PT timepoints, but was 50% lower in CM tissue vs. CTL tissue at d -8. MEC apoptosis was elevated through d 7 PP in CTL tissue, but only to d 1 in PP CM tissue. Milk yield was reduced 53% in CM halves. MEC turnover and PP milk yield was not altered by bST. Real-time RT-PCR analysis of genes regulating cell turnover or milk synthesis included: adenosine 5'-triphosphate binding cassette gene-2 (ABCG2, stem cell marker), '-lactalbumin ('-lac, lactose synthesis) bax (apoptosis), bcl2 (survival), CCAT/enhancer binding protein-ß (CEBP-ß, mammary growth); insulin-like growth factor binding protein 5 (IGFBP5, apoptosis); kinase inhibitor protein p27 (p27, cell cycle arrest). RNA pools were created for PP and PT timepoints for each udder half. Expression of 18S (housekeeping gene) was not changed (P > 0.10) by dry period length (DP) or bST. We failed to detect an effect of bST on expression of any of the genes evaluated. PP '-lac expression was increased 27-fold in CM tissue compared to CTL. During the PT period, '-lac expression was similar between CM and CTL tissue. ABCG2, p27, bax, and IGFBP5 were not affected (P > 0.1) by DP treatment (CTL vs. CM) or gestation status (PP vs. PT). Cyclin D1 and CEBP-ß expression were greater (P < 0.03) during the PP period than PT period, but were not affected by DP length. Expression of bcl2 was increased (P < 0.05) 2.6-fold in PP tissue compared to PT tissue. Results indicate that late-gestation mammary development may be regulated by CEBP-ß, cyclin D1, and bcl2. Differences in milk yield and morphology between CM and CTL tissue were not represented in expression of genes evaluated in this study.