An attempt to omit the dry period over three consecutive lactations in dairy cows

Abstract

In 27 Holstein cows we attempted to omit the dry period over three consecutive lacta- tions, beginning with the first lactation (experimental cows). They were compared to 18 conven- tionally managed cows (control cows) dried off 2 months before calving. Both groups were fed ad libi- tum a complete diet based on grass silage during winter. They were at pasture between May and late October. In the first lactation, only 15 experimental cows could be milked continuously until calv- ing. Average duration of the dry period in the experimental cows was not very different in late third and fourth pregnancies compared to controls. In the second lactation, the 13 experimental cows kept for calculations (among the 15 cows milked continuously) yielded 5.6 kg/day (22%) milk less than control cows (mean for the first 36 weeks), but their milk was much richer in fat (4.0 g/kg) and in pro- teins (3.7 g/kg). The live weight of these cows increased in early lactation (24 kg in the first 2 months) whereas the live weight of control cows decreased (28 kg). Food intake level was unchanged. Blood composition was consistent with the better nutritional balance of continuously milked cows. For the nine experimental cows whose dry period duration was < 5 days in first lactation and > 40 days in second lactation, milk production and feed intake were not different from control cows in the third lactation. dairy cow / dry period omission / milk secretion / nutritional status Rsum -Tentative d'omission de la priode sche pendant trois lactations conscutives chez des vaches laitires. Chez 27 vaches Holstein, nous avons tent de supprimer la priode sche pendant trois lactations conscutives, en commenant la premire lactation. Ces vaches ont t com- pares 18 vaches conduites conventionnellement qui ont t taries 2 mois avant le vlage suivant. Les deux groupes ont t aliments volont avec un rgime complet base d'ensilage d'herbe