Some Genetic Aspects of Persistency in Dairy Cattle

Only a limited number of investigations pertaining to the inheritance of persistency of milk and fat yields in dairy cattle have been reported, and there is considerable disagreement as to the causes of variance in persistency. All recognize non-genetic or environmental factors as playing an important role. Because of the heterogeneity of the data used in reported investigations, it is difficult to segregate the non-genetic from the genetic factors, a fact that has been emphasized by Johansson and Hansson (5).