Lactation Curve of the Sheep from Bulgarian Dairy Synthetic Population

Abstract

The aim of the study was to analyze the lactation curve of ewes from Bulgarian Dairy Synthetic Population depending on test-day milk yield and parity. The analyzed data included 7,920 test – day records of 628 ewes from the herd of Agricultural Institute – Shumen, during the period 2009-2019. A mixed linear model was used and the analytical hypothesis included the factors: year and month of lactation, parity, type of lambing, test day (related to the lactation curve), suckling period, permanent effect of environmental changes, genetic value of the animal, random residual effects. The study established a typical, relatively flat lactation curve varying in depend and on test day and parity. Test-day milk yield is above or equal to the overall mean in the primiparous ewes, close or slightly lower at 2nd to 5th lactation and substantially lower from at 6th and 7th lactation.