Calving disorders of primiparous Holsteins from designed selection studies

Primiparous Holsteins from designed studies were evaluated for edema, dystocia, and retained placenta. Genetic studies were 1) selection for large body size versus small body size, and 2) milk yield selection versus control (no selection). The large body size group was mated to sires with extreme estimates of transmitting ability for tall height and deep and wide bodies. Small body size group was mated to extreme sires for transmitting short height and shallow, narrow bodies. Large and small cows significantly differed only for edema, and small cows had scores suggesting more severe udder edema than large cows. Milk selection group was mated to the four highest sires for PTA milk each year, whereas a control group was mated to 20 randomly selected AI sires that were breed average for PTA milk in 1964. Selection groups for milk yield did not differ significantly for any of the calving disorders.