The efficacy of a standoff pad wintering system to capture urine and mitigate nitrate leaching whilst maintaining acceptable levels of animal performance

Abstract

Wintering of dairy cows on high yielding forage crops is a key contributor towards total farm nitrate leaching loses. High stocking density’s, and subsequent excretion of nitrogen- loaded urine, onto bare, saturated soils results in high nitrate leaching rates. Incorporation of standoff facilities into traditional in situ wintering systems has been suggested as a viable approach to mitigating nitrate leaching., but limited quantitative data exists for percentage of urine captured, and the performance of non-lactating dairy cows wintered under such systems. Two winter systems were compared between June and July 2017 at the Ashley Dene Research and Development Station (ADRDS). Both systems fed fodderbeet (7 KgDM/cow/day fodderbeet, 4 Kg DM/cow/day silage) but in the control system, cows spent 23 hours/day grazing fodderbeet in situ, with a one hour supplement allocation period on a concrete feedpad while the comparison was a standoff pad system, were cows were restricted to a 6 hour fodderbeet allocation period (plus one hour on the feedpad), and spent 17 hours/day on a variety of stand of pad surfaces (stones, sand, woodchip and carpet). To quantify variation in urine deposition between the two systems, PEETER urine sensors were attached to cows and used to measure urination frequency and volume. Urination behavior from eight cows were successfully measured for a period of 24 hours. To compare the suitability of the farms systems from a production perspective, fodderbeet and supplement utilization, cow liveweight, and body condition score were also measured throughout the trial. Results show there was no difference in dry matter utilization (94.2 + ±3.4%), and liveweight gain (580±6.7 gCow/day) between systems. Apparent energy consumption (123 MJME/cow/day) suggested that body condition score gain targets of 0.5 units would be achievable over a 60 day wintering period. Urination behavior was unaffected by wintering system, with average urination event volumes, urination event frequency’s, and total daily urine volumes of (1.8±1.03l/event), (8.37± 4.34 events/day) and (15.12±5.5l/cow/day) were recorded. The percentage of total urine captured under the standoff pad system (82±8.66%) suggest that the expected quantity captured is reflective of the duration of a stand off period. When compared to a 24 hour in situ system, the capture of 82% of urine reduced estimated urine coverage from 54.6% to 9.6% of total paddock area. Based on established leaching values under fodderbeet in stony, Canterbury soil types, this reduction in paddock urine coverage resulted in an estimated reduction in winter nitrate leaching of 31.4 Kg N/ha or 61.6%. It was therefore concluded that stand off pad systems can be effectively used to mitigate winter nitrate leaching whilst maintaining acceptable levels of cow performance.