School of Agriculture, Food and Ecosystem Sciences - Theses
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ItemSpecies composition of improved dairy pastures in Bumthang, Bhutan( 2005)Multilocation studies of forage mixtures since 1970s identified white clover, cocksfoot, tall fescue and Italian ryegrass as appropriate pasture mixture for Bhutanese temperate environments. To date, there has been limited evidence on the long-term sustainability of these mixtures in farmer managed environments. Forty-one grazed pastures and fifty cut pastures were sampled in the elevation range of 2500-3500 m asl. Species composition was expressed in terms of tiller/growing point density of grass and legume species. Tiller core technique was used to measure plant densities. Soil samples were collected from depth profile of 5- 15cm. The dried soil samples were analysed for P, K, pH and texture. Dairy farmers were interviewed to obtain paddock histories and information on defoliation management. The tiller density of cocksfoot was higher in cut pastures though cocksfoot was negatively associated with cutting frequency. Cocksfoot was negatively associated with white clover and Italian ryegrass for both cut and grazed pastures. Soil pH was negatively associated with pasture age. Negative associations between K and pasture age was observed for both cut and grazed pastures. White clover was positively associated with P in grazed pastures. Italian ryegrass was positively associated with P, soil pH and moisture in grazed pastures. Available P was negatively associated with elevation. Cocksfoot abundance in cut pastures has been attributed to cocksfoot being a well adapted hay type species. The lower tiller density of cocksfoot in grazed pastures may be the consequence of continuous grazing without adequate rest period. White clover is positively associated with available P due to white clover being a well known plant that requires adequate levels of available P. The positive association between Italian ryegrass and pH has been explained by the greater availability of P with increasing pH. A decline in the levels of available K in older pastures was related to repeated defoliation without K inputs to replace the losses.
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ItemThe economic evaluation of forage research results( 2004)Three economic analyses were conducted on the results of dairy forage production experiments undertaken in Victoria. The first analysis investigated the level of pasture production increases that would have to be achieved to warrant the investment in different soil modification options. This analysis took pasture production data and using a computer program "UDDER" (Larcombe 1990) generated farm data which was then applied to development budgets. The increase in pasture growth rate required was such that it is unlikely that investment in the soil modification systems tested here will produce a satisfactory return on investment. The second analysis investigated the use of different pasture species combinations on a dairy farm in northern Victoria. A linear programming model was developed that balanced the energy requirements of the milking herd with the energy supplied from pasture and supplements. The results showed that the most profitable mix of pasture depended on the energy supply profile of the pasture and the requirements of the herd. The proportion of autumn and spring calving cows in the herd in part determined the most profitable pasture mix. The effect of grazing management on profit was the subject of the third study. A farm model was constructed that balanced the energy, protein and neutral detergent fibre requirements of the milking herd with that supplied by pasture and supplements and optimised operating profit. The results of a grazing trial conducted in south-west Victoria were entered into the model and the operating profits for each treatment compared. The results suggested that while Operating profit was related to total pasture consumption, the timing of the pasture consumption impacted on operating profit. The results also suggested that grazing frequency may have affected operating profit more than grazing intensity.
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ItemAttributes of pasture influencing the diet of grazing sheep( 2002)This thesis investigated how the composition, productivity and nutritive quality of Phalaris aquatica L. (phalaris) and Trifoliun: subterranean L. (subterranean clover) pasture affected diet selection and intake by sheep in temperate Australia. Field experiments were conducted at the Ginninderra Experiment Station, Canberra, (35 17' S, 149 08' E) and glasshouse experiments at the CSIRO Division of Plant Industry, Black Mountain Laboratories, Canberra, Australia. The effects of different defoliation treatments on the ability of grass and subterranean clover to compete for light were studied in a glasshouse experiment. Regular patterns of phalaris and subterranean clover were planted on a 25 mm grid to create swards with 0% clover, 25% clover, 50% clover, 75% clover and 100% clover by plant number. Swards were either defoliated regularly by clipping to 2, 4, 9 or 15 cm tall or not defoliated and harvested when they reached 2, 4, 9 or 15 cm tall. The distribution of leaf area index within the swards was measured and related to light interception and photosynthesis. Light infiltrated further into the canopy of unclipped swards than clipped swards. Regular clipping created a dense layer of planophile leaves at the top of the canopy, which intercepted most of the incident light, leaving the lower canopy in darkness. Consequently, the lower canopy contributed less to photosynthesis in clipped swards than in unclipped ones. Grass leaves were displayed more prostrate when clipped regularly such that the structure and light interception of grass was similar to clover. In the absence of defoliation, grass leaves were taller than clover, but their erect habit allowed infiltration of light to clover laminae. The relationships between herbage mass, botanical composition, intake and dietary selection by sheep grazing phalaris-subterranean clover pastures were investigated during spring. A range in pasture height (1.2 to 10.2 cm) caused a similar range in herbage mass (370 to 3030 kg DM/ha) and herbage accumulation (-18 to 52 kg/ha/day). A pasture 5 to 6 cm tall, with a leaf area index of 2.0 and an available yield of 1700 kg DM/ha was most productive. The estimated daily pasture intake by sheep ranged from 384 to 1077 g OM. On the shortest pastures, intake was limited by available yield. Intakes increased little after available pasture yield reached 1500kg DM/ha or a pasture height of 5 to 6 cm, but were restricted at pasture heights of 2-3cm or less. There was no evidence for selection in favour of either clover or phalaris, and they were consumed in the same proportion they were present in the pasture. The effect of recent diet on the selection and intake of diet by sheep grazing phalarisclover pastures was investigated. Sheep grazed phalaris, clover or phalaris-clover pasture prior to movement to either a phalaris- or clover-dominant mixture of the two species. The results were complicated by the presence of Vulpia species in the pastures. Where one species dominated the pasture, the diet was predominantly that species. Cases where pasture was a more even mixture of species could not be interpreted successfully, because the alkane concentrations of the pasture species (from which diet composition estimates were made) did not allow the pasture species in the diet to be discriminated with confidence. The daily intake of pasture was affected by previous diet, with animals tending to consume more when moved to a pasture similar to the one they were previously grazing. In an experiment on established phalaris pasture, the diurnal fluctuation in the concentration of water-soluble carbohydrates (WSC) was measured during spring. WSC increased significantly (P = 0.009) from 103 mg/g DM at 0715 hours to 160 mg/g DM at 1300 hours, and did not change further during the next two hours. The concentrations of glucose (17 mg/g DM), fructose (20 mg/g DM), fructan (14 mg/g DM) and "other carbohydrate" (predominantly the carbohydrate moiety of glycosides; 43 mg/g DM) remained relatively constant throughout the daylight period. The increase in concentration of sucrose (33 mg/g DM) was the most significant influence on the increase in WSC (57 mg/g DM). Shading to exclude light prevented the increase in WSC concentration during the day. In a subsequent experiment, a shading treatment was used to create pasture with lower WSC concentration (62 mg/g DM) than an unshaded control (126 mg/g DM). The concentration of the component carbohydrates (i.e. glucose, fructose, sucrose, fructan, "other carbohydrate" and starch) were significantly lower in shaded compared to unshaded pasture. Sheep given free choice between shaded and unshaded pasture exhibited a preference for unshaded pasture over shaded pasture and, on average, 72% of the DM in their diet was unshaded pasture. Whilst no sheep showed preference for the shaded pasture, the proportion of unshaded pasture in their diets varied between 52% and 87% (DM basis). The results are discussed in terms of their implications for grazing management and the development of strategies to improve pasture utilisation and nutritive quality. The role of WSC in diet selection and its importance as a determinant of forage nutritive quality are discussed. The potential benefits of increasing the concentration of WSC in forages by altering agronomic practices or selectively breeding for WSC are discussed.
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ItemFactors influencing the purchases of Pivot fertilisers and Prescription Farming program /cIwan Dhaniyarso( 2000)This study is about the factors influencing the purchases of fertiliser and prescription farming in general and Pivot fertilisers and the Pivot Prescription Farming in particular. The purchase of Pivot fertilisers in this study is defined to be a decision about Pivot as the main fertiliser company. Meanwhile, the purchase of Pivot Prescription Farming is defined as whether or not farmers purchase the Pivot Prescription Farming for the on going activities of their farms. Prescription farming, in this study, refers to services associated with farm inputs such as soil testing and plant analysis. Farmers' decision-making process on the farm inputs, including the choice within a product class, might be dominantly influenced by the problem-solving process. However, the human factors in the farmers' decision is also important. Thus, the farmer's decision-making process is likely to be based on a combination of cognitive and emotional models. In the context of farm income, farmers normally face three stages on the problem of their income allocation. First, allocation to production, consumption and savings. Second, allocation to the categories of generic products in farm activities such as tractors, compound feed and fertilisers. Third, allocation within a product class such as a particular product type or brand. Since the purchase of fertiliser and prescription farming might be categorised as an out-stock situation, the buying process for these inputs only involves stage three. Past research has indicated that the purchase of fertilisers from a particular firm might be affected by quality, price, service, availability of fertiliser, distribution coverage and a specific relationship with the firm. Past studies on the use of soil testing and plant analysis, which are some elements of prescription farming, have shown that price, turnaround time, reliability of results, service and follow up of the service have influenced the use of these services. Additionally, knowledge about available providers, which reflects the amount of information possessed, may influence the purchase. The quantitative analyses in this study use existing data from Pivot Ltd. The method used in this study is logistic regression. The decision on the purchase of Pivot Prescription Farming is involved in the model for the decision on Pivot as the main fertiliser company, and vice versa. For this particular sample, the results revealed that no variable was found to be significant in explaining the decision about Pivot as the main fertiliser company. Only the purchase of Pivot Prescription Fanning and some dummy variables for types of farm and states were significant. The result may indicate that subjective norm appears in the outcome. For the decision about the purchase of the Pivot Prescription Farming, knowledge about service provider, follow up, turnaround time and the decision on Pivot as the main fertiliser company significantly affected the purchase. Those results indicated that farmers who chose Pivot as their main fertiliser company were more likely to purchase the Pivot Prescription Farming, and vice versa. The results also revealed that there is a need to do further research to incorporate with the important issues such as brand loyalty, consumer attitude formation, and the multipersonal influence in farm enterprise, in a better survey with more exhaustive data collection methods.
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ItemEffects of resistance to prehension and structure of pastures on grazing behaviour and intake of dairy cows( 2000)Pasture intake by dairy cows is affected by plant and sward structural characteristics of the pasture. In the meantime, grazing animals are constrained to gather their food bite by bite removing only a portion of the herbage present at the location which they bite. The extent to which grazing animals overcome the constraints imposed by the plant and structural characteristics of the pasture is the major determinant of herbage intake. The experiments which form the basis of this thesis concentrated on determining the role of sward resistance to prehension, measured in situ, as an integrating sward characteristic that determines foraging decisions of cows and the extent to which they defoliate pasture swards. Under rotational grazing systems, a cow is offered an area of pasture that is often smaller than the area from which the cow harvests its bites (defoliated area, DA). The cow therefore faces changing sward conditions during the process of grazing down into the sward and removing bites at successive lower defoliation planes. The defoliation pattern in grazing down the sward profile and the consequent herbage intake and diet composition, are examined in this thesis. A novel apparatus was designed to measure the BFF in situ at different sward profile heights. In the initial experiment, changes in BFF down the sward profile of six pasture species were examined in order to evaluate the mechanical efficiency of defoliating bites at different depths, in terms of bite weight:BFF ratio. The hypothesis tested was that cows remove 30 - 40% of the sward height at each bite due to a mechanical advantage in terms of BW:BFF. The BFF varied more between defoliation strata than between pasture species. The bite weight and BFF increased with the depth of defoliation. The mechanical efficiency of defoliating bites estimated as the BW:BFF ratio declined slightly with bite depth until a depth of about 30 - 40% of the sward height is reached, when the ratio declined more rapidly. Based on these results and those of Wade (1991), four theoretical defoliation planes (DPI, DP2, DP3 & DP4) were set each at 35% of the pre-grazing sward heights to estimate the total area defoliated by grazing cows under different sward conditions. DP2 is the plane of removal of a second bite after a first bite has removed DPI. Three spring grazing experiments were conducted to explore relationships between pasture allowance and/or sward structure and intake dynamics. In the first experiment, cows were offered a herbage allowance (HA) of 50 kg DM/cow/day either as one block with continuous access for 24 hours, or as six equal break rations opened at intervals during a 24 hour period. In the two subsequent experiments, different sward types were created in order to alter the BFF. In the second experiment swards were created with two different surface heights (USH) and in a 2 x 2 factorial, cows were offered two HA (35 and 70 kgDM/cow/day). In the third experiment, swards with three different tiller densities were created and cows were offered a similar HA of 8 kg DM/cow/3 hours. The defoliation pattern, BFF at 30, 50 and 70% of USH, DM intake, grazing behaviour and the energetics of grazing were measured. The major conclusions derived from these experiments are as follows. The average depth of defoliation (DD) increased with sward height and fell between DP2 and DP4. However, the proportion of area defoliated at each defoliation plane declined down the profile, at rates that varied with HA and tiller density but was unaffected by sward height. At a HA of 70 kg, cows barely reached DP4. The area defoliated at DP4 increased with decreasing herbage allowance and decreasing tiller density. The initial bulk density and post-grazed bulk density declined with USH, but the grazed-stratum bulk density was not significantly affected by USH. Therefore, it was concluded that the volume of canopy defoliated was the major determinant of intake. With increasing HA, the average bite weight (BW) increased, prehension bite rate declined but the overall intake rate increased. The time cost of a bite increased with BW. However, the energy expenditure on prehending a bite did not show a consistent relationship with BW. The BFF increased with sward height and tiller density. However, BFF in the leafy layer of 70% of the sward height was not affected by initial sward height or tiller density. The increase in BFF with initial sward height and tiller density was greater in the lower stemmy layer of 30% sward height. The average bite area (BA) and BW increased with HA. Intake was positively correlated with HA (R = 0.49), HM (R = 0.65) and tiller density (R = 0.51). Multiple regression analysis with herbage intake as the dependent variable indicated that, in addition to HM and HA (R2 = 0.887) , inclusion of the difference in BFF between that at 30% USH and that at 70% USH (BFFdif) as a sward characteristic provided an equation with a substantially better fit (R2 = 0.956). DMI = -3.47 + 1.80 HM + 0.225 HA R2 = 0.887 DMI = -2.73 I + 2.76 HM + 0.732 HA - 0.0416 BFFdif R2 = 0.956 It is concluded that the BFFdif has a significant value in integrating the changes in sward characteristics down the profile and is useful in improving the intake model.