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    Lactation curve traits of holstein cows raised at polatlı state farm
    (KAFKAS UNIVERSITY, 2009) Keskin I.; Çilek S.; Ilhan F.
    This study was done to determine lactation curves traits of Holstein cows raised at Polatli{dotless} State Farm. Gamma curve parameters (Yt = atbe-ct) of Wood were used in determination of the types of lactation curve. In this study, values of parameters a, b, c were used in determination of the shape and type of lactation curve. All parameters in typical lactation curves are positive. As one of these parameters is negative, curve is atypical lactation curve. If both b and c parameter are negative, lactation curves are concave. If b parameter is negative and c parameter is positive, lactation curve have negative slope (decreasing type). In total 2581 lactation curves were investigated in this study, 2049 lactation curves were determined as typical (79.39%), 253 lactation curves were determined as concave (9.80%). 279 lactation curves were determined as decreasing type (10.81%). For typical lactation curves, a (beginning yield), b (coefficient of rising), c (coefficient of decreasing), persistency (S), the time after parturition when the peak yield occurs (Tmax), maximum daily peak yield (Ymax) and coefficient of determination of variation (R2) were 27.5±0.18, 0.47±0.008, 0.178±0.0023, 2.7±0.001, 81±2.1, 26.7±0.15, 68.0±0.50, respectively. For concave lactation curves, values of a, b, c, Tmax, Ymax and R2 were found as 23.5±0.42, -0.37±0.016, -0.062±0.0038, 744±159, 16.5±0.42 and 47.8±1.68, respectively. For decreasing typical lactation curves, values of a, b, c, Tmax, S and R2 were found as 27.6±0.41, -0.13±0.007, 0.051±0.0023, -567±327, 2.9±0.05 and 65.8±1.33, respectively.