Farm Trials

Three separate on-farm trials were conducted with the aim of capturing data to test how the system performs. The initial trial was carried out at a farm with a control group of 10 cows to test the weighing algorithm. The system was moved to a large farm with a rotary shed to capture three weeks of data from an entire herd in the aim to determine lameness. The final trial involved one week of data capturing and analysis of a control group of cows.

4.3.1. Trial 1 Setup

The WoP was installed in the exit race of a 20 aside herringbone milking shed operated by Massey University in Palmerston North (see Figure 4.2). The 160 strong dairy herd was made up of an

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assortment of breeds of cows including Holstein-Friesian, Holstein-Friesian / Jersey crossbreed and Jersey. 10 cows were randomly selected from the herd after milking to form a control group to test the walkover weigh algorithm. Each cow was carefully moved to stand on the platform and wait with minimal movement for at least 3 seconds before they were allowed to walk off. The static weight of each cow was then found and recorded against the EID tag number. The group of cows were then made to walk over the platform as naturally as possible by an approved stock handler at least 10 times. This task was completed as quickly as possible before the cows became agitated and sick of walking around in circles. The captured dynamic data was post-processed to find the walkover weight compared to the static weight. See Chapter 6.2 for testing results.

4.3.2. Trial 2 Setup

The WoP was shifted to a large farm located in Kairanga, Palmerston North, which milked between 200 and 800 cows everyday throughout the year. When the WoP was installed in July 2015, approximately 200 cows were being milked twice a day in the winter milking herd, with more being added each day due to calving. During calving the incidence rates of lameness are higher due to additional stresses being placed on the cows’ body (R. Laven, personal communication, March 20, 2015). The 2015 winter season was particularly wet and muddy which also increased the lameness likelihood; consequently it was a perfect time to capture data for the project. Cows walked out of the 60 bail rotary milking shed individually along a 20 m raceway to feed sheds which accommodated 200 cows per shed (four in total). Figure 4.3 shows a feed shed which has

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concrete flooring with a herd of cows eating down both sides. The majority of the herd were Holstein-Friesian or Holstein-Friesian / Jersey crossbreed, which are the two most common breeds (34% and 46% respectively) in New Zealand (DairyNZ, 2015). After half an hour of being in the feed shed the herd were moved to pasture, sometimes a walk as far as 3 km one way. The WoP was installed in the middle of the 20 m raceway under a structure with an arched tin roof. An existing chicane made of metal tubing was 2 m before the platform which helped slow down and single out the cows. A continuous rubber mat was laid over the length of the platform to hide the platform segments so that it seemed like one long platform to the cows (see Figure

4.4). The most suitable time to conduct on-farm assessments of dairy cattle gait is after milking (Flower, 2006) therefore data from the entire herd was captured at this time continuously over a three week period. The morning milking data was not captured (driving to the farm twice a day was not feasible), although the herd still walked over the platform. The cows were not pushed or disturbed while walking over the platform as the idea of this trial was to capture data as naturally as possible without any intervention.

Figure 4.4: WoP during use in raceway Figure 4.3: Herd of cows in feed shed

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The platform was calibrated each day before data was captured to make sure that the correct weight was being displayed. This simply involved the author standing on each section and making sure the static weight was constant and approximately 62 kg. Half way through the three week data gathering trial, Lisa Hine, who is a trained lameness scorer from the Massey University Large Animal Veterinarian Department, visited the farm. Eight final year vet students accompanied her to help with tag reading, writing scores and commenting on particular issues. Each cow was scored after walking over the WoP and down the raceway to the feed shed. A video camera also recorded the scoring session in case particular cows needed to be examined further. See Chapter 6.3.1 for scoring results.

4.3.3. Trial 3 Setup

Three weeks after the initial analysis of trial 2, a further week of data was captured and analysed from the herd, with the focus being on a control group of cows. The control group contained 25 cows - 10 randomly selected healthy (level 0) cows, 3 randomly selected level 1 cows and all identified lame (level 2) cows (12 in total). No level 3 cows were found in the herd during the video analysis scoring. The main reason to focus on a small group of cows instead of the entire herd was to be confident that the scored cows were ‘gold standard’ for their lameness level. Specifically, the lameness scorer was certain that the selected animals’ scores would be a good representation of the population to base the statistical calibration models around. See Chapter 6.4 for results.

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