Beef cows and ewes grazing native pastures are exposed to cycles of
undernutrition that reflect the
seasonal variations of
biomass production. In grazing
dairy cows, the physiological
undernutrition during early
lactation due to increased demands for
lactation and low dry matter intake is exacerbated by the need to get sufficient intake from
pasture and the extra grazing energy
costs.
Undernutrition has profound impacts on
reproduction by affecting multiple reproductive processes at different levels of the reproductive axis. The objective of this
paper is to
review the influence of
undernutrition on reproductive events of the
adult female ruminant, with emphasis on both
grassland and mixed
rain-fed grazing
farming systems. The comparative
endocrinology and reproductive
biology among ewes,
beef and
dairy cows may provide a comprehensive
knowledge of the metabolic and reproductive adaptation to feed restriction.
Understanding the critical underlying physiological mechanisms by which
nutrition affects reproduction is the base of focus
feeding strategy to improve the reproductive performance of the
female ruminant.(AU)