The effect of magnesium oxide supplementation on the fertility of dairy cows grazing fertilized pastures (Short communication)

The Cedara dairy herd of 100 lactating Friesian cows was randomly subdivided into three treatments. A mineral supplement comprising a standard salt + dicalcium phoshate mixture (Treatment 1), the standard + 5% of a commercial trace-mineral premix (Treatment 2) and the standard mix + 10% MgO (Treatment 3) was fed at l30g/cow/day. Inter-calving periods were significantly (P<0,05) reduced from 394 days in Treatment 1 to 373 in Treatment 3 while the services to conception were reduced from 1,94 to 1,54 by magnesium supplementation.