Energy balance, immune function and fertility in the postpartum dairy cow

Infertility remains the main cause requiring disposal of dairy cows. The reasons behind it are multifactorial. Individual cow factors relating to the body condition and health of the animals around calving influence their ability to conceive and remain pregnant. As cows experience a period of nutrient limitation after calving there is a switch towards the increasing use of fatty acids as an energy source in order to conserve limited supplies of glucose. This is promoted by endocrine signalling pathways. IGF1 and leptin concentrations fall and growth hormone (GH) secretion promote lipolysis. At the same time high circulating non-esterified fatty acids (NEFA) concentrations promote insulin resistance in many tissues. The postpartum uterus is exposed to many bacterial pathogens. Its ability to mount an adequate immune defence and repair itself quickly is compromised by the energy deficiency and possible concurrent viral infections such as Bovine Viral Diarrhoea (BVD). This can lead to the development of sub-clinical endometritis, an inflammatory state that perturbs embryo survival leading to prolonged intervals to conception with many cows failing to conceive at all.