|dc.description.abstract||This thesis investigates the use of either liquid urea or effective microorganism solutions to break the parasite lifecycle while outside of its host and reduced larval challenge on pasture. The main aim was to extend in vitro results of urea and Effective micoorganisms on egg development in the field. The field study was performed in a replicated randomized block design at the Lincoln University Lincoln Sheep Research Farm from February 9th 2016 to April 22,2016 on 0.71 ha of newly sown rye grass (Lolium perenne) and white clover (Trifolium repens) pasture. Five-month-old Romney lambs that were naturally infected with gastrointestinal parasites through grazing contaminated pastures and which had not received anthelmintic treatment for a minimum of six weeks rotationally grazed the areas to seed the pasture with fresh contamination for two-days in each plot before being moved to an adjacent plot, giving eight replicates of treatment across time. Immediately upon the removal of lambs from each plot, the areas were topically sprayed with the equivalent of 200 litres per ha of either flowfert N (Ravensdown Ltd) (40 units per ha), effective microorganism mixture (EM; Nature farm Ltd) or water (H₂O) with each treatment replicated twice within each time, giving 16 replicates in total. Following seeding of the pasture with contamination, lambs were given anthelmintic and allowed to graze worm free pastures for seven days. Lambs were weighed and allocated to one of six groups of five animals that were balanced for live weight and then allowed to graze a treatment, grazing each area of the same treatment for two days. Variables such as pasture larval contamination and pasture mass was recorded immediately prior to grazing on each plot with post-grazing pasture mass also recorded. Animal performance and faecal egg count measurements were recorded weekly. Further, on one day of treatment, six trays each of which contained 100 grams of fresh sheep faeces averaging 800 eggs per gram were placed on respective treatment plots, they were sprayed with the respective treatment then left overnight before being taken to the laboratory and cultured for 10 days at 25°C. In addition, a second in vitro larvae culture was performed where the culturing conditions of with and without a plastic bag were compared following the topical application of urea and water to see how each treatment perform under the same environment.
Overall, both Effective microorganism (EM) solutions and urea had little influence on breaking the parasite lifecycle when applied in the field. For pasture larval contamination, lamb FEC, LW and DMI, there were no significant difference. This may reflect the design of the field study which the two days rotation provided an opportunity for half of the eggs to hatch. In vitro results suggested urea has a very potent effect on egg development with 98 % reduction. In the field, urea may have inadvertently encouraged Nematodirus development, which may either be from increased irrigation of 12 h, or the amount of urea that penetrated the faecal mass, may not have being sufficient when dealing with faeces of different moisture or different surface area as well as pH, which was not measured in the field. In addition, in vitro laboratory results, with plastic bag and field study shows little development in egg hatching. Although the disparity is not clearly understood between the field and the in vitro results, the possibility of an artificial high ammonia concentration was ruled out. Overall, urea may provide an opportunity to break the parasite lifecycle, but further investigations are needed in the field.
For the EM treatment, in vitro results showed an increase of 2.5-fold in egg development which did not different from the field trial. Further investigation may be worthwhile to see if treatments of EM can be designed to stimulate larval development when survival on pasture is low at times of the year and non-susceptible stock can be grazed to effectively reduce contamination.||en