Correlation analysis of milk production traits across three generations of Simmental cows
The relationship between milk production traits over whole lactations was evaluated across three generations of Simmental cows (between daughters, dams and granddams) by a corelation analysis with whole lactation traits in the daughter generation being used as the dependent variables (x<sub>1</sub>), and those in the dam and granddam generations being used as the independent variables (x<sub>2</sub> and x<sub>3</sub>). The results were obtained from a sample of 1170 daughters and as many dams and granddams. The correlation of whole lactation milk production traits between daughters, dams and granddams, as calculated by simple, partial and multiple correlation coefficients was very weak or non-existent. All of the calculated simple and partial correlation coefficients were positive and mostly statistically very significant (P<0.01). The calculated coefficients of multiple correlation (R1.23) between lactation length, milk fat content, milk yield, milk fat yield and 4% FCM yield with the expression of the traits in the daughters being used as the dependent variable and that in the dams and granddams as the independent variable were statistically very significant (P<0.01), amounting to 0.091, 0.251, 0.180, 0.133 and 0.153, respectively.
Key words: Simmental breed, production traits, generation, coefficient of partial correlation, coefficient of multiple correlation.