Energy metabolism in the periparturient dairy cow
|GrÚtar Hrafn Hararson, Ingvartsen Klaus L°nne||B═, Lbh═, L.r., S.r.||2005||ReykjavÝk|
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Production diseases i.e. diseases associated with improper nutrition or management are common and very costly in Iceland. The diseases listed in this include: the fat liver syndrome, ketosis, laminitis, mastitis, milk fever, retained placenta, metritis and infertility. The diseases occur mainly around calving. They are all interrelated and form the so-called periparturient disease complex.
The production year of cow can be split up into three phases according to metabolic state of the animal (Holtenius 1994). Two to three weeks before calving a phase of catabolism starts where emphasis is put on the preparation for parturition and the initiation of lactation. This phase will last 8-12 weeks into the lactation depending on the feeding and management strategies and the genetic potential of the animal. A period of equilibrium follows the phase of catabolism where the partition of nutrients neither favours lactation nor increased weight gain. The last period of the production year is a phase of anabolism where the emphasis is put on increased weight gain as a long-term preparation for the next lactation.
The phase of catabolism is the only period causing strain on the cow. In this period for example the energy requirements increase by more than 300% in high yielding cows. These tremendous changes call for a coordination of the biological processes in different tissues resulting in metabolic changes (see table 1) that try to ensure that the cow’s genetic potential for milk yield is exploited but at the same time maintaining physiological homeostasis. When the regulatory mechanism fails one gets physiological imbalance leading to high risk of disease.