Effects of Lactation Stress on Maternal Immune Response in Dairy Cows during Early Stages of Pregnancy

Pregnancy is an immunologically distinct period because the presence of conceptus alloantigens necessitates changes in maternal immune function to prevent immunological rejection of the conceptus. These changes can be observed systemically and at the fetal–maternal interface.

The central theme of FECUND project, funded by the European Union, is to investigate early stage factors affecting reproductive success including the reasons for fertilization failure and events prior to implantation resulting in embryonic loss. Focussed “animal models” address the factors impacting on the establishment of a pregnancy, in order to assess whether dairy cow infertility is primarily a genetic or metabolic problem.

The Energy Balance model compares lactating Holstein cows vs non-lactating cows and heifers, all with similar production and fertility EBVs. Twenty-five pregnant cows and 6 heifers were managed under strictly controlled and standardised conditions, and at calving 13 of the cows entered a normal lactation while 12 were dried off. Heifers and cows were synchronised and embryos were transferred 7 days later. All animals were slaughtered at day 19 when 5 (38%) of the lactating cows were found to be pregnant, 8 (66%) dry cows and 4 (66%) heifers. Blood samples were collected at days 7, 10, 13, 16, 19 and analysed for peripheral blood mononuclear cells (PBMC: monocytes, Treg, NK, γδ cells) by flow cytometry, for PBMC gene expression and for plasma exosome-derived miRNAs and proteins. Samples are being analysed to reveal molecular and physiological variation among the three groups to reveal variations that may impact on reproductive performance.