RESUMO
The area adjacent to the milking parlor, accessible for grazing by lactating dairy cows (i.e., the grazing platform [GP]), can be limited on fragmented pasture-based dairy farms. Such farms, with a moderate overall farm stocking rate, typically have a much higher stocking rate of dairy cows on the GP. This study quantified the effects of farm fragmentation on milk and herbage production and profitability in a whole-farm systems-scale study over 3 yr (2017-2019). Four systems, each with an overall farm stocking rate of 2.5 cows/ha but with different grazing platform stocking rates (GPSR), were examined. The proportions of the overall farm area within the GP were 100%, 83%, 71%, and 63% in each of the 4 systems, respectively. Hence, the 4 systems had a GPSR of 2.5, 3.0, 3.5, and 4.0 cows/ha. The GP was used for grazing and silage (ensiled herbage) production, and the non-GP portion of each GPSR system was used solely for silage production. Concentrate supplementation per cow was the same across all GPSR systems; approximately 10% of the annual feed budget. All systems were compact spring-calving with 24 cows per system. We discovered a lower proportion of grazed herbage in the diet with higher GPSR. All silage produced on the non-GP areas was required to support higher GPSR on each of the systems. Annual herbage production and milk production per cow were not different between GPSR systems, resulting in similar milk production per hectare of the overall system area. The economic implications of different GPSR on fragmented farms were modeled in 2 scenarios: (1) quantifying the cost associated with different levels of farm area fragmentation; (2) investigating the optimum GPSR on fragmented pasture-based dairy farms, depending on variable criteria. A greater level of farm fragmentation lowered the profitability of pasture-based dairy production. Costs of production increased with higher GPSR and longer distances between GP and non-GP areas. At a fixed GP area, it was most profitable to increase GPSR up to 4 cows/ha on the GP when milk price was high, land rental price was low, and shorter distance existed between GP and non-GP areas.
RESUMO
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.
