The results of the survey data were summarised by question. Some of the results could be interpreted directly, for example, whether or not the rats were widespread or localised. However, some questions required further manipulation, or recoding of the data.
Survey performance
The term ‘Non-respondent’ was used for two different instances; either for someone who did not return the survey, or for someone who returned the survey, but did not answer a particular question. If any particular question was missed in a returned survey, that piggery was recorded as a ‘Non-respondent’ for that question only, and this piggery was not included when assessing the results for that question. As a consequence, the total number of piggeries represented for each question may vary slightly. Respondents were used to assess the return rate of the survey. Non-respondents for each question were assessed to see how well the survey was answered by farmers.
Herd characteristics
The number of pigs on the farm was asked for, followed by a brief assessment of the housing types used for each production category. The term “conventional sheds” was used to refer to traditional housing, which typically involves keeping pigs inside buildings in pens, either singularly or in small groups. A different, more recent trend in pork production has been to raise pigs in “eco-barns”. Eco-barns are low-cost shelters in which the pigs can wander freely within the confines of the shed. Lastly, this section included a question on the approximate age of piggery buildings.
Feedstuffs and sources
This section asked general questions on what types and sources of feed were used on the piggery and how they were stored. The use of the term “compound feed” was used in reference to a commercially prepared, pre-mixed feed. This type of feed may, or may not have been heat treated or pelleted and was designed as the complete diet for a
specific production group. The survey enquired about the feeding of by-products, and if so, what type was fed. The term “by-product” included any food that was produced as a consequence of food or other production, where the main product being produced by the process was not pig feed.
Farm environment
Numbers of staff were assessed in relation to total pig numbers on the farm. The average value of pigs/staff ratio was calculated once extreme outliers were removed. When assessing the time until disposal for dead pigs, piglets, and afterbirth, some respondents replied “same day”. This response was recorded as eight hours, as time until disposal was assessed as the maximum time that dead porcine tissue was left in the vicinity of the piggery. This section also questioned what animal species other than pigs were found on or within close proximity of the piggery, and what types of land-use may be found around the piggery.
Rodent activity
Rodents are considered to be directly involved in the transmission of T. spiralis on piggeries. Questions in this section of the survey were designed to assess the levels of rodent activity on piggeries. Rodent activity on the piggery was assessed using three questions each for rats and mice. The six questions regarded how often evidence of live rodents, dead rodents or rodent droppings were seen in the piggery. Farmer responses per question had to be aggregated in order to summarise the outputs from the questions into a single rating, one for rats and one for mice, for each piggery. Evidence of rodents was given a grade by respondents out of three possible options, either ‘Regularly’, ‘Occasionally’ or ‘Never’ seen on the piggery. These grades were allocated a 2, 1, or 0, respectively, by the investigator.
The activity rating from each question was calculated to give an overall outcome value of high, medium, or low activity. Activity was calculated by weighting each grade by question. The response value for live rodents was multiplied by six, dead rats by three, and droppings by one (see Table 3.1). An overall value of less than six was considered to be low activity. Values recorded from six to 11 were considered to indicate medium activity. Values greater than 11 represented high rodent activity. Activity level was scored separately for rats and mice.
Chapter 3 – Piggery survey
Table 3.1 The system used to uniquely identify high, medium, or low activity.
Farmer responsea
Question : How often do you see… b Regularly (2) Occasionally (1) Never (0)
Live rats on your farm? (6) 12 6 0 Dead rats on your farm? (3) 6 3 0 Rat droppings and holes? (1) 2 1 0
a
Value given to each observation level is in brackets.
b
The value that each reply is weighted by to demonstrate the relative importance of that observation to rodent activity is in brackets.
Rodent control
Piggeries were asked what type and form of rodent control was used on their piggery, such as trapping, baiting, other animals, or contracting a professional pest controller. The questionnaire presented a selection of eight brands of commercial rodent bait for assessing which baits were most commonly used in piggeries. Characteristics of these eight baits are outlined in Table 3.2. Lastly, farmers were questioned on disposal methods of dead rodents found on the farm.
Table 3.2 Brand name, toxicant and distributor for eight rodenticide baits available in New Zealand.
Product Name Toxicant Distributor
Pestoff Brodiacoumb Animal Control Products Contrac Bromodioloneb Pest Management Services
Ditrac Diphacinonea Pest Management Services
Racumin Coumatetralyla Bayer-AG
Talon Brodiacoumb Crop Care Holdings Ltd.
Storm Flocoumatenb Cyanamid NZ Ltd.
Kiwicare Coumatetralyla Kiwicare Corporation
Baraki Difethaloneb AgrEvo
a First generation anticoagulant b
Second generation anticoagulant
Trichinella
In order to ascertain the general knowledge of piggery staff on Trichinella, three questions were asked on whether they were aware of the parasite and how pigs or humans may become infected.
Comments
A comments section was given at the end of the questionnaire for farmers to add any further opinions or ideas on the subjects raised in the survey form.