Factors Influencing the Shape of Lactation Curve and Persistency of Holstein Friesian Cows in High Altitude of Eastern Turkey

Data on 371 lactation records pertaining to Holstein Friesian cows reared in high altitude and harsh climatic conditions of Eastern Turkey were analyzed to study the effects of different non-genetic factors on the shape of lactation curve and persistency measures. Calving season affected significantly (P<0.01) a, b, c as well as Tomax, PII/PI and CV from measures of persistency, while days in milk (DIM) at peak yield, peak yield (Y_max) and S were not influenced by calving season. Calving year also affected (P<0.05) DIM at peak yield and a, b, c, S, PII/PI and CV (P<0.01). The significant and positive phenotypic correlation of peak yield with 305 DIM yield suggested that Y_max could be used as a selection criterion to improve milk yield of Holstein Friesian cows reared in high altitude of Eastern Turkey.