This manuscript is the second part of a twin review paper. The title of the companion manuscript is: Reduced Fertility in High-yielding Dairy Cows: Are the Oocyte and Embryo in Danger? Part I: The Importance of Negative Energy Balance and Altered Corpus Luteum Function to the Reduction of Oocyte and Embryo Quality in High-yielding Dairy Cows.
Reduced Fertility in High-yielding Dairy Cows: Are the Oocyte and Embryo in Danger? Part II Mechanisms Linking Nutrition and Reduced Oocyte and Embryo Quality in High-yielding Dairy Cows*
Article first published online: 31 MAR 2008
© 2008 The Authors. Journal compilation © 2008 Blackwell Verlag
Reproduction in Domestic Animals
Volume 43, Issue 5, pages 623–632, October 2008
How to Cite
Leroy, J., Van Soom, A., Opsomer, G., Goovaerts, I. and Bols, P. (2008), Reduced Fertility in High-yielding Dairy Cows: Are the Oocyte and Embryo in Danger? Part II Mechanisms Linking Nutrition and Reduced Oocyte and Embryo Quality in High-yielding Dairy Cows. Reproduction in Domestic Animals, 43: 623–632. doi: 10.1111/j.1439-0531.2007.00961.x
- Issue published online: 19 SEP 2008
- Article first published online: 31 MAR 2008
- Submitted: 14 Jun 2007
Dairy cow fertility has been declining during since the mid-80s and this has given rise to numerous scientific studies in which important parts of the pathogenesis are elucidated. Reduced oocyte and embryo quality are acknowledged as major factors in the widely described low conception rates and in the high prevalence of early embryonic mortality. Apart from the importance of the negative energy balance (NEB) and the associated endocrine and metabolic consequences, there is a growing attention towards the effect of the milk yield promoting diets which are rich in energy and protein. Starch-rich diets can improve the energy status and thus the ovarian activity in the early postpartum period but the oocyte and embryo quality can suffer from such insulinogenic diets. Supplementation of dietary fat has a similar dual effect with a beneficial stimulation of the ovarian steroid production while the oocyte and the embryo display an altered energy metabolism and excessive lipid accumulation. High-protein diets can elevate the ammonia and urea concentrations in the blood, leading to changed intrafollicular, oviductal and uterine environments. Oocytes and embryos are highly sensitive to such changes in their microenvironment, possibly leading to a disturbed maturation, fertilization or early cleavage. Several nutrition-linked mechanisms, through which oocyte and/or embryo quality can be affected in modern dairy cows, well after the period of NEB, are proposed and comprehensively reviewed in the present report.