R. Staufenbiel, Ruth Schmitt, A E Müller, Lydia Staufenbiel
INTRODUCTION: Undersupply and oversupply of dairy cows with essential trace elements should be avoided from the point of view of animal health and environmental pollution. The aim of the study was to proof the results faecal analyzes on the nutritional supply situation with essential trace elements in comparison to measurements from total mixed ration (TMR) analyses. Concentrations of iron (Fe), copper (Cu), zinc (Zn), Mangan (Mn), selenium (Se), cobalt (Co), molybdenum (Mo) were measured as representative multicentric random sample in 574 TMR, 600 pooled faecal and blood samples from dairy cows. Trace elements, Fe in 0 %, Se 18 %, Zn 43 %, Cu 52 %, Co 53 % and Mn 59 %, were within the target range. Undersupply was found in 0 to 8 % and an oversupply in 39 to 100 % of the TMR samples. The tolerance limit for Fe was exceeded in 11 % and for Mo in 13 %. The results indicate the need for optimized ration design. The trace element concentrations in the faecal samples varied over a wide range. Results of pooled faecal samples (n=10 per pool) corresponded closely with the mean values calculated from the individual samples (r2 > 0,9). Correlation between element concentrations in the TMR and faecal samples for Fe (r=0,687), Cu (r=0,675), Zn (r=0,635), Mn (r=0,656), Se (r=0,573), Co (r=0,795), and Mo (r=0,708) were highly significant. No correlations were detected between the element concentrations in the TMR and in the blood samples. The regression analyzes showed a highly significant linear adjustment of the measured value distribution around the regression lines over the entire value range including the zero point. Reference values were calculated for the faecal concentrations of Cu, Zn, Mn, Se and Co. Tolerance reference limits in the TMR were calculated for the faecal concentrations of Fe and Mo. The trace element concentrations in the TMR samples reflect the nutritional supply situation. Knowledge of the nutritional supply situation of the herd is of great importance for the stock management of dairy cow. Fecal sample analyzes can be used as an alternative to TMR examinations to assess the nutritional supply situation.
The European rabbit (Oryctolagus cuniculus) is one of the most successful invasivemammals in Australia, causing substantial economic losses in agriculture and damage tothe environment. The Lockyer Valley in South East Queensland is an important vegetablegrowing region in Australia. Unlike most other regions of Australia where rabbits have beenan endemic problem for a long time, rabbits invaded this region in 2009, causing increasingcrop losses. Many rabbit control methods are available to vegetable growers, but there is norabbit-density threshold available for managing damage to vegetable crops because little isknown of how different densities of rabbits reduce crop yields. In this thesis, I aim todetermine the density thresholds for managing rabbit damage to broccoli and corn crops,and to understand how the broccoli plant compensates for damage. This information willassist vegetable growers in developing an effective management strategy for rabbit control.Known densities of rabbits (0, 3.75, 7.5, 15 and 30 rabbits per hectare) of rabbits wereintroduced into broccoli crops for a predetermined period of time (24 days) at different plantdevelopment stages (single-point damage), and yield losses caused by rabbits weremeasured. The study was conducted in rabbit and predator-proof enclosure at TheUniversity of Queensland (UQ) Gatton campus in 2014 and 2015. When rabbits wereintroduced to broccoli at the seedling stage (14 days after transplanting [DAT]), therelationship between introduced rabbit density (DI) and yield loss (YL) was linear, with YLincreasing with DI. When rabbits were introduced at the establishment stage (28 DAT), therewas no significant relationship between DI and YL. Thus, rabbit control is most critical at theseedling stage. The density threshold (DT) was estimated based on the relationship betweenDI and YL at the seedling stage. DT varied depending on the effectiveness of the controlmethod in reducing DI and on the cost of control as a percentage of the farm-gate value ofbroccoli. For example, DT would need to be 6.54 rabbits per hectare for triggering RABBAIT®1080 carrot baiting, if this method was effective in reducing DI by 94% and if the cost ofbaiting was 1.01% of the farm-gate value of broccoli.To assess the ability of broccoli crops to compensate for damage caused by rabbits,simulated rabbit damage was performed under greenhouse conditions at UQ Gattoncampus from June 2015 to January 2016. Part of each leaf (equivalent to 5%, 10%, 25%,50% and 80%) from each plant was removed manually to simulate these levels of canopydamage at the seedling stage (5 leaves, 17 DAT), establishment stage (7 leaves, 28 DAT) and heading stage (11 leaves, 47 DAT). When damage was imposed at the establishmentand heading stages, the broccoli plants could completely compensate for the damage andmaintain yield. Broccoli that was damaged at the earlier stages of development did notcompletely recover from damage before harvest.To assess the effects of rabbits grazing on corn, an experiment was conducted at rabbit-and predator-proof enclosures on the UQ Gatton campus over the summer cropping seasonin 2016. Corn was grown in 14 enclosures following current agronomic procedures, and wassubjected to grazing by 2 densities of rabbits (44.44 rabbits per hectare and 88.89 rabbitsper hectare) in 3 different growth stages: emergence (7 days after sowing [DAS]), tillering(21 DAS) and tassel (42 DAS) over 7 days (single-point damage). In addition, in oneenclosure zero rabbits were kept, and in another enclosure 2 rabbits were kept continually.Rabbit grazing resulted in a significant decrease in the numbers of plants at the emergencestage, Also, the number of ears of corn per pen was significantly reduced by rabbit grazing.The emergence stage is the critical stage to control rabbits as rabbit grazing resulted in thehighest losses in corn production during the early growth season. This knowledge providesfarmers with a better understanding of the damage caused by rabbits and allows them tomake informed decisions as to whether their crop needs to be protected from rabbits, andwhen rabbits should be managed.These results highlight the need to monitor DI before planting and in the early stages ofplanting (seedling stage of broccoli and emergence stage of corn). The DT estimated in thisthesis will provide the basis for making economically informed decisions on the managementof rabbit damage to broccoli and corn crops. Future studies are required to verify these DT,using free ranging rabbits in the field.