Reproductive hormone use and its association with herd-level factors on Dutch dairy farms
Summary
We studied the use of the 3 commonly used reproductive hormones, namely prostaglandins, GnRH, and
progesterone, and associated herd-level factors on 760 Dutch dairy farms from 5 veterinary clinics. From 2017
to 2019 we collected data on the sales of reproductive hormones, converted this data into the number of reproductive hormone doses conducted, and expressed this as the annual number of reproductive hormone
doses per 100 adult dairy cows. Additional herd-level information was available for 2019. Due to the excess
of zeros in the data set (i.e., a substantial number of farms did not use any hormones), we used a zeroinflated
negative binomial model to identify related herd-level factors for the use of reproductive hormones.
In the entire study period of 2017 to 2019, 5.8% of the dairy farms did not use any reproductive hormones,
with the proportion of nonusers varying between 0.0 and 10.3% per veterinary clinic. This proportion was
around 13.5% on an annual basis. Prostaglandins were the most frequently used reproductive hormone in
Dutch dairy cows (62.9%), followed by GnRH (33.1%) and progesterone (4.0%). Furthermore, participating in
a veterinary herd health management program had a significant effect on reproductive hormone use. These
farms used more reproductive hormones than farms that did not participate in a herd health management
program and were less represented in the group of nonuser farms. Technologies, such as pedometers and
automatic milking systems, also had an effect on reproductive hormone use. The presence of pedometers
or activity monitors did not reduce the use of the reproductive hormones but was associated with a greater
frequency of users. Farms with an automatic milking system used more reproductive hormones than farms
with a conventional milking system. With this study, we have made a first step in achieving transparency in the Dutch dairy industry by providing an objective overview of reproductive hormone use on Dutch dairy farms and identifying associations with some herd-level factors.