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Important Sources of Variation in Milk Flavor¹

Department of Animal Science

E. W. Bird, W. S. Rosenberger and F. E. Nelson²

Department of Dairy and Food Industry, Iowa State University, Ames

ABSTRACT

Milk flavor scores and the incidences of several flavors were analyzed to determine the relative importance of environmental and genetic sources of variation.

Several environmental factors were important. The stage of lactation had significant effects on flavor score and on feed and salty flavor incidences. Also, it accounted for 8% of the variation in oxidized and metallic flavor occurrence. The first 45 days of lactation was the most susceptible stage for development of undesirable flavors.

The year-season of sampling contributed significantly to all flavor characteristics and caused more than one-third of the variance in flavor score and cowy flavor. The importance of year-season effects was attributed to the confounding of year-seasons with differences in summer and winter management practices.

Only small differences were introduced by the cow's age at calving and the judges who tasted the milk. The repeatability of a cow's mean flavor score was .75 when the milk was scored monthly over a ten-month lactation by four judges. An analysis for genetic effects showed that genetic improvement of milk flavor would require a rigorous selection program which would probably reduce the progress in improving milk yield. Hence, we suggest that the effort to improve milk flavor characteristics be devoted to correcting environmental conditions causing inferior flavors.

¹ Journal Paper no. J-5611 of the Iowa Agricultural and Home Economics Experiment Station, Ames, Iowa. Project no. 1514 and 1053. The latter is a part of the North Central Dairy Cattle Breeding Project NC-2.

² Present address: Department of Dairy Science, University of Arizona.