Correcting fresh grass allowance for rejected patches due to excreta in intensive grazing systems for dairy cows

Abstract

Dairy farms with intensive grazing systems combine grazing with supplemental feeding, which can be challenging because an incorrect balance between fresh grass allowance and feed supplementation results in inefficient use of the pasture, lower feed efficiency, and potential decreases in animal production. When estimating fresh grass allowance, we currently do not correct for the formation of rejected patches (RP) surrounding excreta, which can lead to overestimation of the potential fresh grass intake and hampers optimal grazing. In this study, therefore, we aim to quantify the formation of RP in intensive grazing systems and improve the quantification of fresh grass allowance. To do so, we studied 2 grazing systems (i.e., compartmented continuous grazing and strip grazing) that differ in key grazing characteristics, such as pre- and post-grazing heights and period of regrowth. The experiment was performed from April to October in 2016 and 2017 with 60 dairy cows at a fixed stocking rate of 7.5 cows/ha. Average pre-grazing grass height was measured with a rising plate meter. To quantify the formation of RP after grazing, individual grass height measurements were conducted after grazing and classified as RP or not, based on visual assessment. Our analysis showed that the average percentage of grassland covered with RP increased from around 22% at the end of May to around 43% at the end of July/beginning of August, and these percentages do not differ across grazing systems. The percentage of grassland covered with RP should be subtracted from the total grazed area to better estimate true fresh grass allowance.