Comparison of lactation curve using different models for holstein dairy cows

Msc. Thesis COMPARISON OF LACTATION CURVE USING DIFFERENT MODELS FOR HOLSTEIN DAIRY COWS Barış TOPAL Tekirdağ Namık Kemal University Graduate School of Natural and Applied Sciences Department of Animal Science Supervisor: Prof. Dr. Eser Kemal GÜRCAN In present study, lactation biometry was compared by seven different models (quadratic, logarithmic linear, logarithmic quadratic, linear hyperbolic, invers polynomial, Wilmink, Wood) of Holstein breed in Tekirdag. Monthly control milk yield cow's data's were grouped by lactation order and calving season. In this study, was found 305 milk yield according to lactation order; lowest as first lactation (8208,42 kg) and highest as fourth lactation (9864,44 kg). According to Wood model Tmax, Ymax ve S values calculated between 59,83-81,40 days, 42,43±1,47 kg for third Lactation and 8,35±0,17 for first lactation, respectively. According to Wilmink and Wood models were showed atypic lactation as %3 and %4 respectively. In this study was found R2 values for Wood, Wilmink, invers polynomial, linear hyperbolic, logarithmic quadratic, logarithmic linear and quadratic as models respectively, 0,77±0,02; 0,71±0,01; 0,68±0,01; 0,73±0,01; 0,81±0,008; 0,78±0,02 and 0,73±0,02. Wood model is the best goodness of fit model as having the highest R2 values as 0,81±0,08 in 3. lactation. Finally; logarithmic qoadratic was found as suitable in general groups. Key words: Biometry of Lactation, Wood, Logarithmic Quadratic, Wilmink Model