Amazing Grazing; N use efficiency of 60 individual dairy cows under intensive grazing

摘要

The Dutch dairy sector aims to improve nitrogen (N) use efficiency (NUE_N) of intensive dairy farms while supporting grazing. To gain insight into the NUEN of intensive dairy farms, we need insight into the NUEN at cow level. We performed a 2 x 2 factorial grazing trial with 60 Holstein Friesian cows (7.5 cows ha~(-1)), in which we compared NUE_N of individual cows under two grazing systems, i.e. compartmented continuous grazing (CCG) and strip grazing (SG) and two levels of dietary rumen-degradableprotein balance (OEB), i.e. low and high (a difference of500 g OEB cow~(-1) day~(-1)). Grass and supplementary intakes and faecal and milk outputs were quantified and analysed for N content, during two weeks in July and September 2016. Results showed a higher NUE_N for cows in CCG (39%) compared to cows in SG (36%) in July, due to a lower grass (N) intake in CCG. Low OEB showed a higher NUE_N (40%) compared to high OEB (34%). Our results are key to exploring strategies to improve NUE_N of farms that apply innovative grazing systems.