School of Agriculture, Food and Ecosystem Sciences - Theses
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ItemGrazing ecology and high producing dairy cows( 2005)This body of work (82 papers in scientific journals and 2 books) encompasses two broad areas of work. They are 1) growth, nutritive value and management of pastures grazed by dairy cows (40 publications), and 2) supplements for grazing dairy cows, with a particular focus on responses associated with supplement use and digestion in the rumen (44 publications). These two areas of research are inextricably linked and, taken together, have been termed `Grazing Ecology'. Of the 84 publications included, the candidate was the senior or sole author of 67% of them. The chronological development of the work reported includes research on stocking rates reported in the early 1980's through to the development of Diet Check, a decision support tool incorporating much of the information generated during the previous two decades, in the early 2000's. The publications cover aspects of grazing management to optimise growth, persistence and nutritive value of irrigated annual and perennial pastures for dairy cows. Most of this research has incorporated some aspect of stocking rate, whether it be stocking rate per se in long term experiments or frequency and/or intensity of defoliation in shorter term experiments. The aim was to establish optimum grazing strategies that best effected the compromise of maximum intake of pasture of high nutritive value while satisfying the requirements for maintenance of pasture growth and persistence of a balance of desirable pasture species. The research allowed the definition of the intake and nutritive characteristics of pasture grazed by lactating dairy cows under a range of management conditions. At the same time, strategies to effectively feed supplements were investigated. When more than one feed is offered to dairy cows, associative effects play an important role in the eventual responses achieved. Balance of nutrients, particularly in the rumen, and substitution of supplement for pasture in the diet of grazing dairy cows, were the main aspects of the associative effect between feeds considered in the research reported here. Substitution can have a huge effect on the responses obtained from supplements, and the type of supplement, by influencing the balance of nutrients ingested into the rumen, affects the composition of the milk produced. Finally, some attempt has been made to draw much of the information on pasture management and supplementation of grazing dairy cows together for use by dairy farmers and their advisers, and to define gaps in knowledge. This has been done by reviewing the scientific literature, and by the use of modelling to provide simple tools for tactical decision making. Although the research was undertaken in northern Victoria, many of the results apply equally in other areas of the world where pasture constitutes a major proportion of the diet of dairy cows. Victoria currently produces more than 60% of Australia's milk, with northern Victoria producing more than 40% of that. The development of dairying in Victoria mirrors much of the progress of the research reported in this collection of scientific publications. Before 1982, dairy farming was almost totally based on grazed pastures and the use of pasture supplements (hay and silage). A severe drought occurred in 1982, which prompted a serious consideration of the use of supplements for lactating cows grazing pasture. Today, dairy systems in Victoria vary to a huge extent, with the energy provided by pasture ranging from 0 to 100%. Over this period, average milk production has increased, from about 3000L/cow per lactation to more than 5000L/cow. With a fine line separating profit and loss in dairy businesses that basically depend on the price received for manufactured products on overseas markets, both grazed pasture and supplements need to be used optimally. The challenge has been to provide information and tools to allow dairy farmers to achieve this objective. I believe that my research, particularly in relation to pasture intake, substitution and associative effects, has been instrumental in allowing pasture-based dairy farmers to continue to remain viable in Australia, and that many of the principles developed apply wherever pasture constitutes a significant proportion of a cow's diet.
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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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ItemFinishing prime lambs using pulse stubbles, and pulse and cereal grains in the Wimmera region of Victoria( 1998)Three trials were conducted as part of this study. The first trial evaluated faba bean and chick pea stubble as feed source for the finishing of lambs. The second trial evaluated the use of barley and field peas in feed lot rations for lambs, and the final trial evaluated narbon beans and vetch as substitute grains for field peas in feed lot rations for lambs. In the first experiment one hundred and twenty six Poll Dorset x (Border Leicester x Merino) mixed sex lambs with a mean liveweight of 40.0 kg � 0.3 kg were grazed on faba bean (FB) or chick pea (CP) stubble at a stocking rate of 6.5/ha and received a supplement of 300 g/hd/day of barley (+B) or were unsupplemented (-B). There was no significant difference (P>0.05) in average daily gain (ADG) over the duration of the trial between lambs grazing faba bean and chick pea stubble, supplemented with barley or unsupplemented. Lambs supplemented with barley tended (P- 4.06) to have a lower ADG in the first fortnightly period, and had significantly lower (P<0.05) ADG in the second period. This result is supported by the observation of supplemented lambs not grazing the stubble but waiting to be fed the barley supplement. This result was reversed in the third period when supplemented lambs tended (P~.06) to have a higher ADG, and in the final period when the ADG was significantly higher (P<0.05) than the unsupplemented lambs. There was a significant correlation (P<0.01 for faba bean stubble and P<0.05 for chick pea stubble) between ADG of unsupplemented lambs and the quantity of grain residue in the stubble. In the second experiment eighty Border Leicester x Merino mixed sex lambs with a mean liveweight of 27.3 kg � 0.2 kg were fed barley (B) or barley + field peas (B+FP) (60:40) either daily at 800 g/hd/day or ad libitum for 56 days following a 14 day introductory period. Hay was provided ad libitum. There was no significant difference (P>0.05) in ADG between lambs fed the treatment rations. Lambs fed B+FP were significantly different to lambs fed barley in the following: higher carcass weight (P<0.05); fatter (P<0.05); higher dressing percentage (P<0.01); higher estimated carcass weight gain (P<0.05) and lower dry matter intake to estimated carcass weight gain ratio (P<0.05). There was no significant difference (P>0.05) in any of the measured characteristics between lambs fed restricted or lambs fed ad libitum. In the third experiment twenty four Poll Dorset x (Border Leicester x Merino) lambs with a mean liveweight of 28.8 kg � 0.45 kg were individually penned and fed ad libitum a ration of narbon beans (NB), vetch (V) or field peas (FP) mixed with wheat and formulated to 16% crude protein. Milled hay was provided separately ad libitum. There was no significant difference (P>0.05) in growth rate, carcass weight, dressing percentage, feed intake, or dry matter intake to liveweight gain ratio between lambs fed the three rations. The growth rate and feed intake of lambs fed FP was more consistent than lambs fed NB or V. Scouring was observed in lambs fed V. There was highly significant (P<0.001) separation and selection of wheat in the NB and FP based rations. Further research needs to be carried out to evaluate meat quality of lambs fed narbon beans and vetch, in particular to determine if there is any effect on flavour of the meat. The use of pulse stubbles, combined with lot feeding can form a feeding system to enable lambs to be finished in the autumn-winter period in the Wimmera region. The growth rate of lambs grazing pulse stubbles is dependent on the quantity of grain residue on the ground. The growth rate can be maintained as grain level declines by the introduction of a barley supplement. Lot feeding can be used to finish lambs when pulse stubbles have been grazed out. A combination of a cereal grain and a pulse grain formulated to 16% crude protein can be fed ad libitum. Hay can be provided separately ad libitum, or a more controlled intake of hay can be achieved by feeding a calculated amount daily.
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ItemThe relative value of tagasaste and lucerne as supplementary feeds for sheep( 1993)Chamaecytisus palmensis (Tagasaste) is a leguminous perennial shrub which grows well in a range of climatic zones. Tagasaste was introduced from the Canary Islands to Australia in 1879 and a number of farmers are growing the shrub for fodder production and soil conservation. The most economical means of utilizing tagasaste in Australia appears to be direct grazing by sheep. This thesis reports on a study of tagasaste and lucerne as a supplementary summer feed for sheep in the Strathfieldsaye Research Station, East Gippsland, Victoria. The purpose of the present study was to investigate the relative value of feeding tagasaste and lucerne (Medicago sativa) as a supplementary feed for sheep during summer. Growth performance of sheep, dry matter consumed and the chemical composition of feeds were examined over the four months of the experimental period. The 240 two year old Merino sheep were divided into 12 groups for grazing eight plots of tagasaste and four plots of lucerne as a supplement to summer pasture. Each plot had been fenced into four or six subplots for tagasaste or lucerne respectively, to allow stock to be rotated in four months. The estimation of the dry matter consumed in each subplot was done by selecting 50 sample quadrats before and after grazing for each experimental month. The mean liveweight gain for all sheep in the lucerne plots (11.3 kg/head) was not significantly different from tagasaste (10.6 kg/head) at the end of the experiment. The mean total change in standing dry matter due to grazing in the tagasaste treatment (5360 kg/ha) over the four months was greater than for the lucerne treatment (3384 kg/ha). The overall daily growth efficiency over the daily dry matter (LW (g)/DM (g)) eaten by sheep in tagasaste was 0.20% and 0.34% for lucerne over the experimental period. In both treatments the pattern of pasture dry matter consumption did not resemble the pattern of liveweight gain. The digestibility and total nitrogen content of feed types were not significantly different between trial months. However, the leaf part of tagasaste had significantly greater values than other feed types during the trial although lucerne leaf was not measured. During the trial there was no loss of liveweight in sheep fed tagasaste or lucerne as a supplement. A second experiment indicated that tagasaste regrowth after grazing was significantly better in lightly grazed plots than in heavily grazed plots suggesting that farmers remove stock before all leaf has been eaten. In conclusion, the results of this study suggest that there is scope for the summer grazing tagasaste as a supplement to dry pasture however lucerne remains a better feed than tagasaste on this site. The high quality of tagasaste foliage (leaf) and low rate of liveweight gain of the experimental sheep suggest that further study is necessary to identify the cause of low stock performance.