Abstract
A long grazing season improves the profitability of pasture-based dairy production. It can entail grazing under wet soil conditions and the risk of damaging swards. Housing cows either temporarily or completely while soil moisture is high can avoid damaging swards. An experiment with 4 grazing systems was conducted over 3 yr (Sep. 1, 2013, to Aug. 31, 2016). The purpose was to evaluate whether soil moisture measurements are an effective decision support to assess the risk of treading damage and effects on pasture productivity and dairy cow performance during wet soil conditions. Access time to pasture between February and December of each grazing season was dependent on volumetric soil moisture content (VSMC, m3/m3) measured each morning: Control = cows were housed at VSMC >0.5 and otherwise allowed 22 h/d access to pasture; S<7 = cows were housed on days with VSMC >0.7 and otherwise allowed 22 h/d access to pasture; S7-6 = cows were housed at VSMC >0.7 and allowed 8 h/d access to pasture at VSMC between 0.7 and 0.6 and 22 h/d access at VSMC ≤0.6; S7-5 = cows were housed at VSMC >0.7 and allowed 8 h/d access to pasture at VSMC between 0.7 and 0.5 and 22 h/d access at VSMC ≤0.5. Cows with 8-h access per day received no other feeding when housed. All herds were compact spring-calving, with a mean calving date of Feb. 19. Mean stocking rate was 2.57 cows/ha. Measurements of VSMC provided an objective indicator for the risk of treading damage. Less time spent at pasture under wet soil conditions lowered treading damage but had no effect on annual pasture production (mean 14.8 t of organic matter/ha). Annual milk solids production per cow was lowest for the control herd (485 kg) and not different between the other systems (503 kg). Reducing treading damage to swards did not improve productivity or profitability of the grazing systems. Nevertheless, measuring soil moisture was a useful decision support for assessing the risk of treading damage when turning cows out to pasture.
Highlights
A long grazing season improves the profitability of pasture-based dairy production (Läpple et al, 2012; Hanrahan et al, 2018)
A,bMean values in the same row with different superscripts differ between grazing systems (P < 0.05). 1S0.7 and otherwise allowed 22 h/d access to pasture; S7–6 = cows were housed at VSMC >0.7 and allowed 8 h/d access to pasture at VSMC between 0.7 and 0.6 and 22 h/d access at VSMC ≤0.6; S7–5 = cows were housed at VSMC >0.7 and allowed 8 h/d access to pasture at VSMC between 0.7 and 0.5 and 22 h/d access at VSMC ≤0.5; control = cows were housed at VSMC >0.5 and otherwise allowed 22 h/d access to pasture. 2On overall farm area. *P < 0.05, ***P < 0.001, NSP > 0.05
Restricting access time to pasture based on VSMC effectively lowered the severity of treading damage, and, measurements of VSMC provided an objective indicator of the risk of treading damage in this study
Summary
A long grazing season improves the profitability of pasture-based dairy production (Läpple et al, 2012; Hanrahan et al, 2018). Grazing dairy cows, during the winter, spring, and autumn, can damage both the sward and upper soil layers, which can lower pasture production (Pietola et al, 2005; Drewry et al, 2008; Phelan et al, 2013; Tuñon et al, 2014). Treading damage by the hooves of grazing animals, which is a plastic deformation of the soil surface, is most likely to occur under wet soil conditions (Drewry et al, 2008; Phelan et al, 2013). At higher latitudes of the temperate zones, soil moisture content is typically highest during the winter, spring, and autumn due to seasonally higher rainfall combined with low evapotranspiration. To achieve a long grazing season, it is often necessary to turn cows out to pasture under less-than-optimal soil moisture conditions
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