The effect of pregnancy on milk yield in Bulgarian Murrah buffalo cows.

A study assigning 694 gestation periods (lactations) of 294 Bulgarian Murrah buffalo cows with recorded milk yield, bred on the farm of Agriscultural Institue - Shumen during the period 1967-2001, was initiated with the objective to estimate the effect of pregnancy - expressed as the specific effect of gestation month - on test-day milk yield. Using linear LS-analyses, it was established that the effect of pregnancy is expressed in significant dramatic reduction in daily milk yield after gestation month five, resulting in 12.9 to 14.4% deterioration per 305-day lactation. It is pronounced only in the high-yielding buffaloes and is analogical to that in high-yielding bovine cows. The effect of the first post conception months is negligible in both cases with short and long days open.