The long-term weekly grab sampling strategy takes a grab sample every week and is therefore better equipped to capture the increase in NH3 emissions during a fattening period. However, as with the single grab sampling strategy, samples for the long-term weekly grab sampling strategy were only taken during daytime (between 9 a.m. and 5 p.m.). Nevertheless, for all days and both datasets, all of the 1000 simulated long-term weekly grab sampling strategies estimated an EF that is within 15% of the true EF. This good precision for the long-term weekly grab sampling strategy originates from the fact that the increase in NH3 emissions during a fattening period is well captured. This indicates also that taking grab samples on a regular basis (on a specific day and/or once every week) during daytime can be sufficient to obtain an estimate of the EF that is within 15% of the true value.