The first results of the long-term milk study at Dairy Campus within the 'Customized Lactation' project show that extending the voluntary waiting time after calving to insemination (VWP) from 50 to 125 or even 200 days resulted in an equal milk production per day between calving time for the heifers.
In cows, extending the voluntary waiting period after calving to insemination to 125
days also had no effect on the production per day, compared to a VWP of 50 days. Extending the VWP in cows to 200 days reduced production per day.
At the Dairy Campus, 150 cows were assigned to a VWP of 50, 125 or 200 days and then followed during the entire lactation and the start of the subsequent lactation.
The aim of this study was to identify the consequences of consciously extending the VWP for animal health and production efficiency.
Daily production equal
Results of the study show that the day production in heifers with an extended lactation did not differ between voluntary waiting periods. This means that insemination could be delayed for up to 200 days after calving without affecting production per day, when this is averaged over the entire period between two calving moments. However, when heifers are inseminated later, they take longer to become second calf cows. Since second calf cows are generally more productive than heifers, extending the calving interval for heifers can still lead to milk loss at flock level.
Previously pregnant with a VWP of 200 days
Cows with a VWP of 200 days became pregnant earlier after the end of the VWP than cows with a VWP of 125 or 50 days. The better fertility for cows with a VWP of 200 days can possibly be explained by a higher proportion of "normal" (regular) heats around the end of the VWP, and a lower milk production around the end of the VWP. Cows with a VWP of 125 days also had a higher proportion of regular cycles and lower milk production at the end of the VWP compared to the cows with a VWP of 50 days, but this was not related to a better fertilization rate or fewer open days after the end of the VWP.
At the end of lactation, in the last 6 weeks before drying, the production after a VWP of 125 days or 200 days was lower compared to the production after a VWP of 50
days. A lower production during drying off can lower the risk of new udder infections in the drying period and improves animal welfare during drying off by lowering the udder pressure.
Suitability for extended lactation
It is expected that some cows will be more suitable for extended lactation than other cows. Currently, the data from this experiment are being used to identify traits predicting cow health and milk production at an extended voluntary insemination waiting period. Results of this sub-study are expected in early 2021.
The 'Customized Lactation' project is funded by ZuivelNL and the Ministry of
Agriculture, Nature Management and Food Quality. CRV contributes to the
practical translation and delivery of data. In addition, parallel to the trial on Dairy Campus, there is also a network of livestock farmers who are engaged
in "Sustainable milking".