Effects of diseases on test day milk yield and body weight of dairy cows from Danish research herds.

The pre- and postdisease interrelationships of energy corrected test day milk yield and body weight of dairy cows caused by mastitis, three reproductive disorders (retained placenta, metritis, cystic ovaries), and seven metabolic disorders (milk fever, ketosis, decreased rumen motility, enteritis, left displaced abomasum, right displaced abomasum, and off feed) were quantified by using mixed models analysis with repeated measures of continuous data. The data were weekly recordings from 4414 lactations collected in three Danish research herds. High milk yield was a risk factor for ketosis and enteritis. Heavier primiparous cows were more likely to contract mastitis. Milk yield was decreased for a disease-specific period for all study diseases except cystic ovaries and right displaced abomasum. Metabolic disorders had a detrimental effect on body weight. The highest weight loss (69 kg) was associated with left displaced abomasum. The persistence of the weight loss differed considerably among study diseases. Almost all weight loss occurred up to and including the initial week after diagnosis, which emphasized the detrimental effect of the subclinical stage. However, weekly measured body weight seemed superior to weekly energy corrected test day milk yield for disease detection only for decreased rumen motility and left displaced abomasum. This study demonstrates the importance of the predisease level for accurate estimation of the loss of milk yield and body weight from disease.