Can the dynamic of milk Ca content throughout lactation be an indicator of the effects of management system and diets on bone mobilization in dairy cows ?

Abstract : During lactations, dairy cows faces huge calcium requirements due to milk production. Because of the fast increase in those requirements at the beginning of the lactation, the organism of dairy cows can hardly adapt by increasing intake and digestive calcium absorption. The organism must mobilize calcium from its storage pool, bones, which will replenish later in lactation. Those cycles of bone mobilization and reconstitution remain impossible to quantify for important number of dairy cows and the consequences of an incomplete bone reconstitution on following lactation remain unknown. The aim of this PhD was to develop an indicator of the phenomenon of bone mobilization and reconstitution during lactation.Several factors increasing bone mobilization have been identified, such as breed, parity or diet. However, the cycles of bone mobilization and reconstitution could not be related to variation in milk Ca and P content. However, it has been showed that, an insufficient Ca supply in early lactation does not always induce a higher bone mobilization, as it has been described in the literature, but can be compensated by an increase in digestive absorption capacity. The thesis also showed the need to quantify the consequences on insufficient dietary calcium supply on dairy cows’ milk production and health throughout lactation.
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Pierre Gaignon. Can the dynamic of milk Ca content throughout lactation be an indicator of the effects of management system and diets on bone mobilization in dairy cows ?. Animal biology. Agrocampus Ouest, 2018. English. ⟨NNT : 2018NSARB316⟩. ⟨tel-02178374⟩

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