Invited Review: New Perspectives on the Roles of Nutrition and Metabolic Priorities in the Subfertility of High-Producing Dairy Cows¹

Proposed “ideal body condition score profile” for dairy cows to minimize the effect of energy balance on reproductive failure. Body condition score is presented for the 5–, 8–, and 10–point scales.

The feedback-regulated systems that control the reproductive axis (shaded area A) and the somatotropic axis (shaded area B) interact at several levels and thus link nutritional and metabolic inputs into the reproductive process. Note that for the reproductive axis, FSH is omitted because it does not appear to limit dairy cow fertility. In addition, for the sake of clarity, the thyroid and adrenocortical axes have been omitted: they are both regulated by their own feedback loops in the brain-pituitary system, both are intimately linked with lactation, both respond to metabolic inputs, and both affect the reproductive and somatotropic systems, so they introduce inputs from stressors such as high ambient temperature, disease, and the antagonistic interactions associated with establishment of social dominance. With respect to sex-steroid feedback, positive feedback for induction of the preovulatory surge has been omitted.