Milk production parameters in early lactation: potential risk factors of cystic ovarian disease in Dutch dairy cows

The aim of this field study was to investigate whether the incidence of cystic ovarian disease (COD) in dairy cows was related to milk production parameters (milk yield, milk fat and protein) in early lactation with special emphasis on the negative energy balance (NEB). The diagnosis of COD was made by rectal palpation performed by veterinarians experienced in gynaecology. Data used for this field study were collected from November 1986 onwards. The dataset consisted of 6911 lactations (3891 cows) on 29 herds including 600 cases of COD (8.7%). Lactations in the COD group had higher average maximum productions of milk, energy corrected milk, milk fat and protein than lactations in the non-COD group. The average maximum milk fat:protein ratio did not significantly differ between the groups. Daily changes of the average maximum milk fat and protein percentage and of total milk fat and protein yield were calculated and divided into four groups depending on the day of first milk recording. No significant relations were found between changes in milk fat and protein percentage and total milk fat and protein yield, and the incidence of COD. It is concluded that elevated average peak milk yield, milk fat and protein yield in early lactation are risk factors for the incidence of COD, but the average milk fat:protein ratio is not. In this field study changes in milk fat percentage and milk fat yield, indicative for the presence of NEB, did not show a relation with the incidence of COD in early lactating cows. (C) 2002 Elsevier Science B.V. All rights reserved.