Milk yield and persistency of lactation of Saanen goats: relationships between lactation, stress and epithelial cells

• Grant number: 13/08653-3
• Support Opportunities: Regular Research Grants
• Start date: July 01, 2013
• End date: June 30, 2015
• Field of knowledge: Agronomical Sciences - Animal Husbandry - Animal Production
• Principal Investigator: João Alberto Negrão
• Grantee: João Alberto Negrão
• Host Institution: Faculdade de Zootecnia e Engenharia de Alimentos (FZEA). Universidade de São Paulo (USP). Pirassununga , SP, Brazil

Abstract

The increase in milk yield is related to number and activity of epithelial cells. Consequently, the decline in milk production after peak lactation occurs not only due to a decrease in the secretion activity of epithelial cells, but mainly as a result of a reduction in the numbers of these cells by apoptosis. It seems that greater lactation persistence might be achieved by an increase in the cell survival rate. Since stress is known to increase metabolic rate via cortisol, the stress might increase the apoptosis rate and thereby reduce lactation persistence. Furthermore, it is important to study stress susceptibility during lactation, and relationships between cortisol, GR and MR receptors in epithelial cells of the mammary gland. To this purpose, experimental goats will be study during all lactation and submit at two experiments: in vivo (Experiment I) and in vitro (Experiment II). In vivo all experimental goats will be submit to physiological stress by ACTH administration or Placebo solution. Afterwards, epithelial cells will be submit in vitro to different cortisol concentration. During all lactation, milk production (milk yield, alveolar and cisternal milk) and milk quality (microbiological, physical and chemical characteristics) will be measured. At 60, 120 e 180 days of lactation experimental goats will receive ACTH or Placebo solution, and blood samples and biopsy of the mammary tissue will be samples for analysis of cortisol, DNA, RNA, PCNA, TUNEL, MR e GR receptors. In this context, this project propose to study productive, physiological and molecular responses of Saanen goats to stress, and their influence in apoptosis of epithelial cells and lactation persistence. (AU)