[The effect of subclinical and clinical mastitis on milk production in cattle]

Subclinical mastitis may cause a decrease in production in the infected quarters, particularly in heifers. Investigations on monozygotic twins in New Zealand showed that this decrease in production of the infected quarter is compensated by an increased production of the normal parallel quarters in secundiparous and older cows. It can be concluded from these findings that a decrease in milk production should be calculated on the basis of cow production rather than on that of quarter production. From the point of view of loss of milk production, particular attention should be paid to heifers in the prevention of mastitis.