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Vertebrate reproductive science and technology
RESEARCH ARTICLE

Subclinical mastitis disrupts oocyte cytoplasmic maturation in association with reduced developmental competence and impaired gene expression in preimplantation bovine embryos

Z. Roth A C , S. Asaf A , O. Furman A , Y. Lavon A , D. Kalo A , D. Wolfenson A and G. Leitner B
+ Author Affiliations
- Author Affiliations

A Department of Animal Sciences, Faculty of Agriculture, Food and Environment, The Hebrew University, Rehovot 7610000, Israel.

B Mastitis Laboratory, The Veterinary Institute, Bet Dagan 50250, Israel.

C Corresponding author. Email: roth@agri.huji.ac.il

Reproduction, Fertility and Development 28(11) 1653-1662 https://doi.org/10.1071/RD14431
Submitted: 8 November 2014  Accepted: 19 March 2015   Published: 20 April 2015

Abstract

Subclinical chronic mastitis was induced to examine the effects on oocyte developmental competence. Uninfected Holstein cows were intramammary administrated with serial (every 48 h for 20 days) low doses of toxin of Staphylococcus aureus origin (Gram-positive; G+), endotoxin of Escherichia coli origin (Gram-negative; G–) or sterile saline (control). Follicular fluid of toxin- and saline-treated cows was aspirated from preovulatory follicles and used as maturation medium. Oocytes harvested from ovaries collected at the abattoir were matured and then fertilised and cultured for 8 days. The percentage of oocytes undergoing nuclear maturation, determined by meiotic nuclear stages, did not differ between groups. Cytoplasmic maturation, determined by cortical granule distribution, was affected by both toxins (P < 0.05). The percentage of oocytes cleaving to 2- and 4-cell embryos and of embryos developing to the blastocyst stage was lower in both toxin-treated groups than in the control group (P < 0.05). There was no significant difference in the total cell number in Day 8 blastocysts among the groups; however, the apoptotic index was higher in both toxin-treated groups compared with control (P < 0.05). The relative abundance of prostaglandin-endoperoxide synthase 2 (prostaglandin G/H synthase and cyclo-oxygenase; PTGS2) mRNA increased, whereas that of growth differentiation factor 9 (GDF9) decreased in matured oocytes. In addition, PTGS2 expression increased and POU class 5 homeobox 1 (POU5F1) expression decreased in 4-cell embryos developed from both G+ and G– oocytes. Thus, regardless of toxin type, subclinical mastitis disrupts oocyte cytoplasmic maturation and alters gene expression in association with reduced developmental competence.

Additional keywords: dairy cows, fertility, mammary gland.


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