School of Agriculture, Food and Ecosystem Sciences - Theses
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ItemA systems analysis approach to drought reserves in the Hamilton region( 1971)Following a discussion of drought strategies available to the grazier, one particular strategy, the holding of drought fodder reserves, is examined in detail. The study estimates the least-cost fodder reserves for a range of stocking rate-pasture production regimes in the Hamilton region. The amount of hay feeding required on any stocking-pasture regime is determined from a simulation model of the grazing complex. In this model, three levels of pasture production are stocked at rates ranging from one to ten wethers per acre. The pasture production assumed ranges from "excellent" (i.e. equivalent to the Hamilton Research Station pastures which produce about 10,000 lb. dry matter per annum) to "poor" (35% less). The climatic inputs into the grazing model are the date of Autumn break, for which a formula is derived, and the June to October rainfall. The pasture sub-model is specified and used to derive the pasture which is "grown" in the grazing model. The sheep aspects of the model are reviewed in detail to derive the relationships which are used in the next set of four sub-models in which animal intake is simulated and liveweight changes determined. This set of four sub-models provides for the four situations of animal intake which may be met. These are: The intake of green pasture alone (i.e. all pasture grown after the Autumn Break); the intake of hay alone; the intake of hay and green pasture together; the intake of hay and dry pasture (pasture remaining when the Autumn Break occurs and dry pasture alone which are handled in the same sub-model) The grazing model was validated for the years 1965-67 using data from the Pastoral Research Station, Hamilton, and showed good agreement for all three years simulated, one of which featured a severe drought. Drought feeding requirements (hay) are determined for each of the years 1879 to 1967 and for the ten stocking rate-pasture production regimes, using specific hay feeding rules. These rules, which aim at sheep survival, do not attempt to specify optimum feeding rates per sheep, and any change in them could significantly alter the drought requirements for any of the regimes studied. Furthermore, the estimates are Lased on the assumption that all sheep are fed through the drought. A pre-drought strategy which permitted the sale of certain classes of sheep at some stage during drought would entail lower feed requirements and might have a lower expected cost, especially at high acquisition costs for feed and low replacement costs for sheep. An inventory analysis is then undertaken, based on a 12 month planning period, which utilises the hay feeding probabilities generated in the grazing model, and provides estimates of the least-cost hay reserve. In contrast to previous studies, the price of hay is related to drought length in calculating the penalty cost of inadequate reserves. The effects of varying several parameters of the inventory model are then examined. The parameters varied are hay costs ($4, $10 and $16 per ton), interest rates (7%, 20% and 50%), and salvage values, and these vary in association with the parameters varied in the grazing model (stocking rate, pasture production and the area closed for hay). At the intermediate values for pasture production and hay cost and a 7 per cent per annum interest rate, the minimum-cost reserve rises sharply, from 2 bales per acre at 2 wethers per acre, to 4.5 bales per acre at 3 wethers per acre, 8 bales per acre at 4 wethers per acre, and 15 bales per acre at 5 wethers per acre. The minimum-cost reserve was found to be relatively insensitive to changes in acquisition costs, except at low stocking rates, where a change in reserve of one or two half-bales per sheep was common as acquisition cost varied over the three levels. The effect of interest rates was also examined for the average pasture regime. On the lowest level of hay acquisition cost, ($4 per ton) increasing the rate of interest from 7 to 50 per cent caused reductions of only one half-bale per sheep. However, at high acqusition cost ($16 per ton) raising the interest rate to 20 per cent resulted in a considerable reduction in the minimum-cost reserve, especially on the lower stocking rates, and raising the interest rate to 50 per cent made holding fodder reserves uneconomic for any stocking rate. One measure of the risk in holding various levels of fodder reserve is the standard deviation of the total expected cost. As expected, it was found that this declines as the reserve is expanded to the maximum ever required. However, only a small reduction in standard deviation results from expanding the reserve beyond the minimum-cost level. Finally, estimates were made of the income-maximising stocking rate for each level of pasture production and hay cost, with the wool price at 30, 40 and 50 cents per lb.. At the intermediate values for pasture production (8,000 lb. D.M.) and hay cost ($10 per ton), and with wool at 30 cents per lb. net, the income-maximising stocking rate was 3 wethers per acre. Each increase of 10 cents per lb. in the wool price was generally associated with an increase of one or two wethers per acre in the income-maximising stocking rate. An increase of 2,000 lb. D.M. (from "average" to "excellent") in average annual pasture production was generally associated with an increase of one wether per acre in the income-maximising stocking rate. A reduction of 1,500 lb. from "average" to "poor" pasture. production reduced the income-maximising stocking rate by about one wether per acre. Increasing the hay cost from $4 to $10 per ton reduced the profit-maximising stocking rate by one wether per acre for all combinations of pasture production and wool price examined. However, a further increase in acquisition cost from $10 to $16 per ton only caused a further reduction in the income-maximising stocking rate at the poor level of pasture production: with average pasture production there was little change and with excellent production there was no change in the income-maximising stocking rate.
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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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ItemThe digestion of ruminant feeds in vitro( 1974)Systems of feed evaluation require the determination of the digestibility of the components of the feeds. The determination of digestibility in vivo is laborious and expensive, thus considerable research effort has been directed towards the determination of techniques to measure digestibility in vitro. The development of laboratory methods for assessing the digestibility of ruminant feeds is discussed. A two- stage technique, composed of microbial and enzymatic digestion stages, has currently been applied to the analysis of herbages, mixed forages, wood, brassicas, concentrates and silages. The digestibility of substrates determined by means of the two-stage in vitro method may be affected by the method of preparation of the substrate, the pH and duration of the microbial digestion, and the ratio of the rumen fluid to the buffer solution. The source of the rumen fluid may also affect digestibility in vitro , since the activity of this. fluid varies between species, individuals within species and the diet of the donor animals. Variation due to the diet of the donor may be minimized by means of a diet with an adequate crude protein content. Regression analyses are presented relating in vivo digestibilities to values of digestibility estimated by various laboratory procedures. In vivo digestibility may be predicted more accurately by the in vitro digestibility technique than by the nylon bag technique or by chemical methods of evaluation. However, methods incorporating the digestibility of cell wall material, digestion by fungal cellulase or summative equations of chemical constituents may be used as alternatives to the two-stage digestibility technique. The review is concluded with a discussion of the relationships between in vitro digestibility values of feeds and the values of total digestible nutrients, index of nutritive value, starch equivalent, voluntary intake, digestible energy and metabolizable energy , the last two of which are currently used to formulate rations for ruminants.
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ItemEstimating digestibility of supplement diets by near infra-red reflectance spectroscopy (NIRS)( 1995)This study was undertaken to investigate the effectiveness of the NIRS technique for predicting nutrient composition, intake and digestibility in sheep receiving chaff fed alone (T1) or supplemented with either barley (T2) or cotton seed meal (CSM) (T3). There were three experimental periods, each of 21 days duration. For diet T1 intake was 944 g and digestibility was 60 %. For the diet containing barley (T2), chaff intake declined by 35 % so that total intake remained constant while digestibility increased by 10 %. For diet T3 total DM intake increased by 259g but digestibility remained constant. The digestibility values for the three diets ranged from 60.1- 65.7 + 0.69 SEM (P < 0.001). Prediction of CP, OM and NDF concentrations can be achieved with feed or faecal analysis by NIRS to a degree of accuracy that agrees closely with conventional laboratory methods. Use of the appropriate NIRS calibration equation permitted accurate prediction of digestibility but tended to underestimate DM intake. The results from this study indicate that NIRS-based estimates of DMD and DMI generally agreed more closely with observed values than conventional estimates, when compared using the GrazFeed nutritional management system.
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ItemEffect of hardness on intake and storage quality of urea molasses block by sheep( 1990)This thesis presents a research programme undertaken to examine the possibility to develop a suitable composition for urea molasses block ideal for Bangladesh climatic conditions, using locally available ingredients. The investigations were carried out within the general context of using rice husk ash (RHA) as a binding agent for urea molasses block and to replace a reasonable proportion of lime in the block. Attention was focussed on the extent of tooth wear and possible causes of variability in intake of urea molasses block and effects of long-term feeding of such blocks on animal performance. A review of literature enabled the presentation in chapter 2 of the various factors affecting intake of urea molasses block, properties of rice husk ash and its opportunity of uses for different purposes and finally the major causes of tooth wear with possible consequences on animals. Reported effects of the level of urea, essential mineral elements, sources of phosphorus in block, climatic conditions and placement of block, animal's previous experience with such food and hardness or compressive strength of urea molasses block are reviewed. It is concluded that increasing the level of urea from 5-10% in the block tends to stimulate intake. A very high level of calcium and low phosphorus or any mineral imbalances tend to decrease its intake through its effects in long-term. Pre-weaning experience and other management strategies have also been found to increase intake of urea molasses block. Supplementation of poor quality cereal straw diets with urea molasses blocks has given variable responses in the reviewed reports. The reasons for this variability are numerous and can be attributed in part to the characteristics of basal diet being supplemented, to animal factors such as species, physiological state and health and to the conditions under which measurements have been made. No studies have been made on the efficacy of use of rice husk ash as binding agent for urea molasses. Chapters 3 and 4 report on experiment in which six different types of urea molasses blocks with varying levels of lime and rice husk ash were prepared and their hardness was measured in terms of compressive strength (kg) both under normal environmental conditions and after placing these blocks in a hot room for 5 days at temperatures and relative humidity of 25- 35C and 50-80% respectively. It is found that 40% rice husk ash and 60% lime (out of total 8% binding agents) is the best ratio in terms of compressive strength. Blocks with more than 8% binding agent have better strength when both rice husk ash and lime are in equal proportion. After compressive strength test four different types of urea molasses blocks were selected for a feeding experiment lasting 13 weeks including two weeks of adjustment period. Barley straw and urea molasses block were offered ad libitum to sheep along with 30 g of lupin/day/sheep. The blocks and straw together constituted four different dietary treatments and three sheep received each dietary treatment. The average initial liveweight was 41.4 kg (range33-59). The organic matter contents of urea molasses blocks were 739-802 g/kg DM. The nitrogen content of straw was 7.1 g/kg DM. The nitrogen contents of blocks ranged from 54.4 to 56.3 g/kg DM. The in vitro organic matter digestibility of straw was 51.8% and of the urea molasses blocks ranged from 92-97%. Comparisons of straw offered with that refused indicated no difference in organic matter, nitrogen and acid detergent fibre content. However, there was a highly significant (P<0.001) difference in neutral detergent fibre (NDF) and silica content between straw offered and refused. The mean daily intake of straw among four different groups of sheep ranged from 31.6 to 40 g DM/kg W0.75. The highest being observed in the group consuming block with 6% rice husk ash and 6% lime. Mean daily intake of urea molasses block was also highest in that group and the range of intake among four different groups was 9.8- 15.2 g DM/kg W0.75. The ratio of intake of block: straw was highest for group D (0.44: 1), followed by blocks A, C and B. The overall correlation between straw and block intake was 0.70. There was no significant difference between intakes of straw and block among the four groups. However, some animals were found to reduce feed intake drastically at the beginning and at the end of the experiment. This reduction in feed intake was much frequently observed with group D consuming the lime only (8%) block. Two out of three animals in this group reduced feed intake during the last three weeks of the experiment. This reduction in feed intake was highly significant (P<0.01) compared to previous intake by the same group or others. There was no significant difference in mean daily liveweight change over the experimental period. Reduction in feed intake in group D during the last three weeks resulted in a highly significant (P<0.01) loss in liveweight compared to liveweight changes of the previous weeks of the same group or other groups of sheep. There was no significant difference in tooth wear among four groups of sheep. Addition of rice hush ash at higher level (10%) will not cause tooth wear. There was no significant difference in nitrogen balance of the four groups of sheep. The highest N balance was observed with group A. Three out of four groups of sheep were in positive nitrogen balance, but positive nitrogen balance was not reflected in liveweight gain, probably due to error in faeces and urine collection, sampling or nitrogen loss during analysis of sample. Alternatively nitrogen balance trial week may not be truly representative of the whole period. There was significant (P<0.05) difference in water consumption between group of animals. The level of silica excreted in faeces was related to silica level in urea molasses block (r=0.94). It is concluded that urea molasses block intake is related to straw intake, factors likely to increase straw intake will also increase block intake. Blocks with high level of lime (8% or more) has harmful effect on animal performance in long-term feeding probably due to mineral imbalances. The effect most likely to affect animal performance is severe reduction in feed intake. Urea molasses blocks containing rice husk ash have not been found to cause any such effect in long-term feeding and better compressive strength can also be obtained with rice husk ash. It is found that at least 40% of lime (out of total 8%) could be replaced with rice husk ash without altering the compressive strength (storage quality) and a better quality block could be made with 12% binding agent, 6% rice husk ash and 6% lime. So the use of rice husk ash as binding agent for urea molasses block could be recommended.
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