Innovative Technology and Sustainable Development of Organic - 1.

4.2.4 GPS logging of defecation and urination
A hand-held GPS navigator (Garmin®, eTrex Venture) with an estimated accuracy of 5 m was used on
two separate days for all three treatments, to register all urinations and all defecations. This was done
by observation during the whole of the grazing periods of 4, 6.5 and 9 h for each treatment for 2 days.
All loggings were shown in real time and were classified as being urine or manure. Additionally, on
three separate days for each treatment, every 10 min for a period of 5 min, the number of defecations
and urinations were registered. Each paddock was virtually divided into 10 equal areas, numbered from
1 to 10, to register the spatial distribution. The quadrate containing the drinking trough and entrance
was numbered as 1. The spatial distribution of manure and urine was scored in relation to the
quadrates.
4.2.5 GPS logging of cow traffic and calculations
During the trial, three different cows were equipped with a neck collar, TU400 GPS Tracker (Blue Sky,
Telemetry®), from which the data were downloaded and used to generate and calculate the cows’
route, distance walked and velocity. To test whether the movement behaviour was different between
the grazing treatments P4, P6.5 and P9, the frequency at which the cow exceeded the velocities 0.5 m
s −1 and 1.0 m s −1 was estimated and compared for the three treatments. The cows wearing the collar
were carefully chosen as being average in milk yield and observed behaviour. The accuracy was
documented within 5 m for each logging point. The tracker was programmed to log every minute and
to give a position when sufficient satellites (at least five) could be contacted. If this could not be
established, the observation was recorded as ‘no position’. On days when more than 10 consecutive
minutes had ‘no position’, the data were discarded. The registering days for defecation and urination
(registered with GPS Garmin®), were scheduled to coincide with the collar registrations in the same
field. As the weather is known to influence cows’ grazing behaviour and urination/defecation
frequency, climate data (precipitation, minimum temperature, maximum temperature and average
temperature) were registered and implemented. The calculations of average velocity and frequency of
walking velocity exceeding 0.5 and 1.0 m s −1 were made on the basis of 4 days of registration.
4.2.6 N balance and slurry production
The nitrogen (N) balance was calculated per cow per day, and was based on the assumption that:
Nexcreted = Nfeed – (Nmilk + Nweight gain)
where
Nexcreted = Nurine + Nmanure
Nfeed = Nherbage + Nsupplement
Nmilk = milk crude protein produced in g day −1 /6.36
Nweight gain = weight gain in g day −1 26/1000
�
Nherbage and Nsupplement = crude protein intake in g day −1 /6.25
All formulas and calculation factors are from Poulsen and Kristensen (1998).
Protein intake and output were calculated on the basis of the analysis results of herbage, barn
supplementary feed, and milk, combined with estimated herbage intake by grazing, and measured
supplement intake in the barn, milk production and daily weight gain, which are presented in
Thesis Frank W. Oudshoorn 63