Simulation-aided development of the Hawaii swine research programme

A computer model is presented to estimate the quantitative impact of future research/extension activities in various aspects of swine production on the profit of an average swine producer in Hawaii. The model was designed and used to generate information for making decisions regarding funding of future research/extension projects in the swine production area. The computer model has two components. The first simulates the biological production behaviour of a typical pig enterprise of Hawaii. The General Purpose Simulation System (GPSS) language was used to model the stochastic nature of the production. For a given set of biological parameters, this component provides annual production levels, feed consumption and statistics for selecting the capacity of various building facilities. The second component computes annual revenues, costs and rate of return to capital investment over the analysis period by using discounted cash flow method. In addition to other cost and price data, it uses the output of the first component as input.     

Simulation of growth and production in sheep-model 1: A computer program to estimate energy and nitrogen utilisation,body composition and empty liveweight change,day by day for sheep of any age

A computer program based on empirical relationships is described. It predicts daily energy and nitrogen utilisation repetitively for sheep of any age, before, during and after weaning; provision is also made for pregnancy, lactation and cold stress. Input information includes: intake, protein content and digestibility of the diet; age, empty body weight, fat content and feeding activity of the sheep; ambient temperature and wind speed; times of shearing and mating.Metabolisable energy from milk and/or dry feed is estimated and energy requirements for maintenance, including the cost of feeding activities and homeostasis in the cold, are deducted to obtain energy balance. The amount of amino acid nitrogen absorbed from the small intestine is estimated, and nitrogen balance in body tissues and wool is calculated from this, allowing for body weight and net energy intake. Potential wool growth is calculated from nitrogen and energy intakes, and potential conceptus growth or milk production is estimated primarily from stage of pregnancy or lactation. The use of nitrogen and energy for these products is assessed and balances of energy and nitrogen in body tissues are then obtained by difference. If achievement of the potential rates of production in pregnant or lactating animals would cause excessive loss of energy or nitrogen from body tissues, production of wool and conceptus or milk is reduced sufficiently to avoid this problem. Gain or loss of body fat and protein, and hence change of empty live weight, are finally derived and the animal parameters are incremented before proceeding to calculation for the next day.Evidence is presented that the model is stable in predicting lifetime performance, and that predictions of growth curves, body composition and various nutritional parameters are reasonably accurate in a variety of circumstances.     

Economic significance of wool in meat production systems

The contribution of wool to ewe output declines in relative terms as the number and value of lambs reared per ewe increases. This is illustrated by the spectrum of sheep production systems in Great Britain, from extensive hill production where wool accounts for 18% of ewe output, to intensive production out of the main lambing season, where wool only accounts for 6% of ewe output. The ratio of wool production to sheep meat production and their respective prices vary greatly between countries.In Great Britain, as technical efficiency increases, the relative, but not necessarily the absolute, contribution of wool to output declines. Changes in production systems and management, aimed at improving slaughter lamb output per hectare, will also bring about a consequential increase in wool production per hectare.Because wool represents an appreciably lower part of the output in meat producing systems than lamb sales, increases in wool prices have a relatively small effect on gross margins. In lowland flocks a 20% increase in wool prices only increases the gross margin per ewe by 3·1%.Although wool output is considerably less important than lamb sales in Britain it is, nevertheless, worthwhile for the producer to pay close attention to the fleeces produced in order to ensure that he receives the highest returns possible. This is illustrated by reference to the variation in wool returns per ewe between flocks.Fleece weights and quality have a high heritability and are rapidly improved by selection. However, the relative economic value of the annual genetic improvement in increasing the number of lambs reared per ewe is worth five times as much as the annual genetic improvement in fleece weight in lowland flocks; in hill flocks this falls to only twice the value.     

Long-term stochastic simulation of mountain beef cattle herds under diverse management strategies

A stochastic simulation model was used to assess the effects of diverse management strategies on beef herds under mountain conditions in the Spanish Pyrenees. Animals grazed on different seasonal resources (valley meadows, forest pastures and mountain pastures) and were fed with forages and concentrates during winter. The simulated management strategies were winter calving (WC, weaning at 180 days), autumn calving (AC, weaning at 160 days), 8-month calving (8MC, weaning at 180 days), and two calvings in 3 years, with weaning taking place at either 170 days of age (2C3Y) or at 9 months (2C3Y9 M). Each strategy was tested for two types of production systems: (i) cow-calf farms that market calves just after weaning; and (ii) cow-calf/finishing farms that fatten the animals by means of an intensive feeding system until achieving a suitable weight for slaughter. A herd of 100 cows was simulated over 15 years, but only data obtained after reaching the steady state (year 6) was used in the analysis. The strategies were evaluated by considering reproductive, productive and economic performance. The percentages of pregnant cows at the end of the mating season were highest for 8MC, 2C3Y and 2C3Y9M (between 92% and 94%). The percentage was intermediate for AC (88%) and lowest for WC (78%), which also showed greater variability between years. The two strategies that extensified management (2C3Y, 2C3Y9M) produced, as expected, a lower number of calves weaned per year (59 and 60), whereas this figure was the highest for 8MC (90). Although AC and 8MC resulted in higher productive performances, the increased labour requirements and winter feeding costs resulted in low economic margins for these strategies, which also meant poorer utilization of natural resources. In economic terms, WC was the best strategy for cow-calf/finishing farms, whereas 2C3Y was the worst of the two types of production systems, although it resulted in the most intense utilization of grazing resources. The long lactating period of 2C3Y9M did not affect the reproductive performance of cows, so this strategy yielded the highest economic margin at weaning. The extensification strategies (2C3Y and 2C3Y9M) were less sensitive to changes in the price of feedstuffs. The information obtained from the simulation of the different strategies is useful for evaluating the possible trade-offs between production, economics, use of natural resources and labour requirements.     

Evidence of farm-level synergies in mixed-farming systems in the Australian Wheat-Sheep Zone

Synergies are reported for mixed-enterprise farming systems in a benchmarking group in the Wheat-Sheep Zone in New South Wales, Australia. A stochastic input distance function is estimated and a measure of synergies is calculated, based on the second cross partial derivative of output variables in the distance function. Evidence is presented of strong synergies from complementarity between sheep and beef enterprises, sheep and crop enterprises, and beef and crop enterprises.     

Efficiency differentials in the traditional agriculture of Northern Nigeria

It is generally accepted that farmers operating in traditional agricultural systems are highly efficient, given the resources and technology available to them. This has led to farm policies in third world countries which place a high emphasis on capital investments.This paper uses a frontier production function analysis to generate firm specific efficiency indices for traditional farms in three different areas in northern Nigeria. Computed indices are then employed in identifying both inter- and intra-area efficiency differentials. The relationships between technical efficiency and commonly used farm performance measures are also examined.The results indicate that efficiency scores range between 0·67 and 1·00. This implies that least efficient farmers could have obtained gross value of output 24–36% above their actual output. Thus, the results reported in this paper are not in total support of the conventional belief that no increase in traditional agricultural output is possible by a more efficient use of factors at the disposal of farmers. One implication of these findings is that extension programmes based on the experience of more successful farmers, even with traditional practice, can yield modest dividends.     

Identification and selection of technology for a specific agricultural region: A case study of sheep husbandry and dryland farming in the northern Negev of Israel

The chances that innovative technology will succeed in a given agricultural region are difficult to determine in advance. Information that would point to the likely or optimum course of development would be very useful for development planning and applied agricultural research administration. An approach is presented whereby the diffusion of new technology can be analysed in the context of a developing region. The development of sheep husbandry and wheat cultivation systems in a semi-arid agropastoral region in the northern Negev of Israel is used as a case study. The approach employed involves defining the input/output relations of a set of technologies based on wheat cultivation and on an increasingly intensive range of sheep production systems. The region is defined by its borders, land classes, physical and financial capital, available labour, plant and animal genetic stock and climatic conditions. An optimum mix of technologies over a development period is determined by using a multiperiod linear programming routine. The technology assessment is then conducted by varying the future socio-economic scenarios of the region and analysing the response of the model.The results indicated that the most fertile sheep breed, the Finn cross, would be selected only if labour were plentiful and cheap. It would also be selected whenever the demand for sheep created high shadow prices—especially at the beginning of a development period. The local, relatively extensive, breed of sheep (Awassi) is maintained over a long period even when meat: grain price ratios are high. Eventually, it tends to phase out in favour of a more intensive breed, the German Mutton Merino. The high price ratio did not result in massive transfer to confined, intensive husbandry but increased the use of improved pasture on cultivable land.     

Maasai herd and flock structures in relation to livestock wealth,climate and development

Information was obtained on the structure of the herds and flocks of a sample of 41 households on the three Maasai Group Ranches in Kenya. The purpose of the survey was to contribute to an intensive study of the livestock production system, and also to assess the amount of information that could be obtained from a herd structure study on its own. Differences in herd structure were related to the livestock wealth of the household, the stage of development of the Group Ranch as well as to the variation in climate, and production alternatives.Data from more than 5100 cattle revealed that Maasai herds contained less steers in 1982 (18%) than in 1968 (22%). The proportion of mature steers had also dropped from 5% (1968) to 2% (1982), with maximum valves of 3·2% on the most developed ranch and 2% for the wealthiest stratum of households. A high percentage of females had been retained (56%) giving a herd structure characteristic of subsistence production with milk as a primary output. This structure also caters for a strong market in immature animals and gives the herd a high potential for recovery after a drought. There appeared to be a trend towards increased use of introduced bulls, notably Sahiwal on the Small East African Zebu, with increased Group Ranch Development. However, this trend was confounded by a decreasing aridity gradient with increased development.On two of the ranches for which 1968 counts were available, cattle numbers were 119% of their previous value whereas small stock were 470%. The reason appears to be that increased sedentarisation without adequate range management has resulted in a severe reduction in grasses, and their replacement by forbs. These plants are more palatable to small stock which are better able to exploit the degraded habitat.Information from more than 2730 sheep and 2300 goats revealed that poor households preferred goats and richer households, sheep. The Small East African Goat was ubiquitous, but the most developed ranch had crossed Dorper onto Maasai sheep whereas the least developed and most arid ranch had introduced Somali Blackhead sheep. The Dorper crossbred catered for a market for mutton whereas the Blackhead was primarily for home consumption of fat.The conclusion is that Group Ranch Development has not projected the Maasai into commercial beef ranching as originally planned, but their production system has not stood still. A study of herd structures was a good way of demonstrating the evolution of the system. The method was simple but was dependent for its success on fairly involved and time-consuming sampling and data collection procedures.     

Using the GrassGro decision support tool to evaluate some objective criteria for the definition of exceptional drought

Some objective criteria for defining conditions of exceptional drought were evaluated using the GrassGro decision support tool. In two analyses, pasture and animal production were simulated from historical daily weather records for the last 95 years at sites in central New South Wales. The first analysis successfully discriminated between two sites 40 km apart, only one of which had received an effective fall of rain during a long dry spell. In the second analysis, production was simulated at one of these sites to identify the exceptional droughts over the 95-year period from the percentage ranking of moving averages of monthly rainfall, available green herbage and the supplementary feed required for sheep survival. Greater summer rainfall in the second half of the period meant that most of the exceptional droughts were in the first half. We suggest that a monitoring system based on shire-by-shire simulations of appropriate grazing systems, using 18-month moving averages of the weight of supplementary feed required for the survival of the animals, may be a practicable way of establishing exceptional drought circumstances.     

Simulated effects of changing strategies on production performance of Gobra Zebu cattle

Analyses of various management strategies available for the production of Gobra Zebu cattle at Dahra Research Station were conducted using a dynamic cattle production simulation model. Growth, milk production, forage and management characteristics collected at the station were the major input data used. Effects of the management strategies on production performances were predicted by examining changes in breeding season, breeding age, weaning age and supplementation regimes on productivity indices. The indices used were efficiency of nutrient utilization (ENU), defined as liveweight sold per 100 kg DM consumed, and cow productivity index (CPI), defined as liveweight sold per cow exposed. When females were exposed to calve first at 3 years of age, the ENU (94·4) and CPI (4·04) were highest for breeding from September to November and lowest (77·93 and 3·43, respectively) for breeding from July to September. Weaning at 7 months of age resulted in the highest ENU and CPI (94·89 and 3·95) while weaning at 5 months generated the lowest ENU and CPI (83·93 and 3·58). Among all feeding alternatives, the highest ENU (105·84) and CPI (4·21) were obtained when the entire cow herd was supplemented from May to July. Supplementation of mature cows only was the most desirable strategy among the selective supplemental feeding practices with regard to cow age classes. Results provided valuable guidelines for selecting management practices likely to increase Gobra Zebu productivity.     

Development of a mathematical model to study the impacts of production and management policies on the herd dynamics and profitability of dairy goats

The reduction in goat milk production and the competitiveness of more profitable activities have increased the adoption of measures to enhance goat milk and meat around the world. A simulation model was built to evaluate the dynamics of a dairy goat herd under different scenarios of production. A System Dynamics approach was used to identify management policies that could affect the behaviour of the herd over 10 years of simulation using data from a dairy goat herd in Brazil. The impact of reproductive and mortality rates, one or two annual reproductive cycles on production, and economic health of dairy goats on changes in the herd dynamics were evaluated. Simulations indicated that small changes in reproduction and mortality rates and milk price can considerably affect the dynamics of the herd as well as the financial health of the production system. The interferences created to visualize the effects were not immediately realized because of intrinsic delays in the system. The comparison of models with one or two breeding seasons indicated that the latter was considerably more profitable and had a faster turnover. It was also found that the two breeding season had a greater capacity to support reduction in milk price that could generate financial instability in the production system. It was concluded that mathematical models can be used to predict impacts in management policies on herd dynamics and sensitivity to support the dairy goat activity showing its viability as an agricultural activity that can contribute to the production and incomes in small farms.     

云南省干旱分区及农业旱灾风险区划研究

探讨了干旱分区及农业旱灾风险区划的方法,并在云南省开展了应用研究。选取流域地貌特征指数、多年平均干旱指数和75%保证率年降雨量负距平百分率指标,采用主成分分析法对云南省进行干旱自然分区进行了研究;将干旱分区成果作为旱灾风险区划指标之一,综合考虑旱灾风险危险性、脆弱性及易损性因素建立了旱灾风险区划指标体系,并根据多层次模糊综合评估结果进行了云南农业旱灾风险区划研究。结果表明,滇东北是干旱易发区,滇西南是干旱轻发区或少发区;滇东北属于旱灾高风险区,滇西北属于旱灾低风险区。分区成果与云南省的历史干旱情况基本符合,表明基于主成分的干旱自然分区和基于构成要素的旱灾风险区划方法是可行的。     

A pasture growth model for use in a whole-farm dairy production model

A generalised climate driven pasture growth model is described and evaluated by comparison to field observation. The model describes dry matter production and green-dead tissue flow dynamics for grazed temperate swards, especially perennial ryegrass (Lolium perenne). The model includes a unique feature to account for light interception by non photosynthetic tissue. Extrapolation across environments occurs by the interaction of climate variables with three parameters that tune the model to a site. These parameters reflect the influence of soil fertility and sward species composition on production patterns. They are: (1) the efficiency of radiant energy use for photosynthesis, (2) the timing of reproductive development and (3) the relative efficiency of radiant energy use in vegetative compared to reproductive swards. Initial parameter settings were derived from data from a sheep grazing experiment in New Zealand. In this paper the ability to describe pasture production under dairy grazing at a different site is confirmed. When the three available parameters were calibrated for the dairy site, all but two of the 42 seasonal estimates of pasture production were within the 95% confidence interval for mean measured production. The model is being used as a component of a whole-farm dairy production model.     

Modelling the dynamics of sheep flocks in Egypt

A structured multi-period Goal Programming model for the determination of the optimal age structure of a flock of sheep given a set of sheep breeder goals is used to evaluate three sheep breeding flock cases in Egypt. The cases are: flocks with a fixed size over an arbitrary period of 5 years, flocks with a growing size over the same period and flocks with a fixed size and stable age structure over time. The breeder's goals considered are the total increase of kilograms weaned and the total wool produced by the flock, the decrease of the average flock age and the flock initial purchase cost.The model was applied on the local Rahmany Egyptian sheep. Results for the three considered cases are presented and discussed.     

基于DEA的灌区生产效率分析——以江苏省为例

针对当前灌区农业生产效率评价多采用单项投入与产出指标的不足,引入数据包络分析(DEA)方法,设定表征生产效率的投入产出指标体系,利用CCR模型对江苏省35个灌区相对生产效率进行了比较研究.相对效率分析表明,江苏省综合效率整体不高,灌区间差异较大,全省平均值为0.634,其中3个灌区为DEA有效;不同区域农业生产技术的利用及推广程度相当,灌区相对生产效率的不均衡主要由生产规模不合理引起.可以通过减少投入来提升非DEA有效灌区的生产效率,所有非DEA有效灌区改进生产效率能节约的有效灌溉面积、水资源及农业人口分别占投入量的20.7%,13.3%,9.4%.相对DEA效率的比较可为灌区生产效率的改进途径、农业节水潜力的计算等提供新的思路.     

A simulation model of a lowland sheep system

A simulation model of a lowland sheep system has been constructed. Biological components are modelled using state variables and flow equations, the variation between animals in a flock being simulated using random number generators. The model was validated against experimental results. Management rules were included to evaluate the effect of different management regimes on biological and economic output from the system and some example results are presented.     

气吸滚筒阵列式棉花精密排种器设计与试验

针对气吸式棉花精密排种器输气管路结构复杂、能耗大以及排种单体只能实现单行播种等问题,采用阵列吸孔吸种、侧向气吹清种等方式,设计了一种气吸滚筒阵列式棉花精密排种器,确定了该排种器关键零部件的结构参数,建立了充种过程的力学模型。以棉花种子为播种对象,以滚筒转速、吸孔直径、气室负压为影响因子,以合格指数、漏播指数和重播指数为排种性能指标,进行二次旋转正交组合试验,建立各影响因子与排种性能指标之间的回归模型,分析了各因子对排种性能的影响规律。采用多目标优化方法,确定最佳参数组合:滚筒转速为15.5 r/min,吸孔直径为3.5 mm,气室负压为4.2 k Pa,此时排种器的合格指数为93.5%、漏播指数为2.0%、重播指数为4.5%。经试验验证,试验结果与优化结果基本一致,满足棉花精密播种的要求。在此基础上进行了排种适应性试验,试验对象为几何特性存在一定差异的新陆早48号、新陆早52号、新陆早60号3种棉花种子,结果表明:合格指数均大于92%,漏播指数均小于3%,重播指数均小于5%,说明该排种器对不同品种的棉花种子具有一定的排种适应性。     

基于SPEI的贵州省分区干旱时空演变特征

[目的]干旱对贵州省水循环及水资源管理系统造成严重破坏,科学合理地认识干旱时空演变对抗旱减灾及社会稳定至关重要。[方法]利用贵州省18个气象站点1960 2012年逐月降水和平均气温数据计算标准化降水蒸散指数SPEI评估干旱,采用M-K趋势检验、B-G分割法、极点对称模态分解法ESMD和反距离权重插值法分析了贵州省分区分时段干旱时空演变特征。[结果]贵州省月、季和年尺度SPEI序列均呈波动下降趋势,其中夏季和冬季SPEI序列变化未通过显著性检验,且20世纪60 90年代,贵州省各分区干湿变化具有较强的一致性,21世纪各分区的干湿变化不具有明显的一致性;以黔西北年SPEI为例,基于ESMD分解法得到3个模态分量IMF和1个趋势项R,从R看出干旱指数整体上呈波动“减小-增大”趋势,分析IMF1-IMF3振荡可得黔西北地区干旱具有2.1、7.6和26.5a的周期特征,且年代际周期26.5a在干旱变化中起主导作用,ESMD法在非线性、非平稳时间序列周期及趋势分析中应用效果较好;依据B-G分割法检测结果,得到1960 1986年、1987 2003年和2004 2012年3个研究时段,2004 2012年黔西北地区的冬旱强度和黔西南地区的春旱频率达到最大,分别为1.82和77.78%,2004 2012年四季干旱强度明显增大,且1986 2012年贵州省高强度干旱呈现由北向南转移趋势,1960 2003年四季干旱高频区呈现由东南向西北转移趋势,1960 2012年各分区四季干旱频率呈现增加趋势。[结论]贵州省各分区呈干旱化趋势,且干旱频率和强度呈现不同程度的增加。     

环县农户肉羊养殖意愿影响因素分析

本文基于环县五个乡镇的调研数据,结合环县肉羊发展现状,运用二元Logit模型对农户养殖意愿的影响因素进行实证分析,结果表明：劳动力人数、是否有充足的饲草料、自然环境、养殖年限、肉羊品种、政府补贴和肉羊价格对农户养殖意愿有显著的正向影响,其中劳动力人数、自然因素、肉羊品种和肉羊价格对农户养殖意愿影响最为显著。疫病风险对农户养殖意愿有显著负向影响。最后提出政府应增加牧草产量保险,提升农户在销售过程中的话语权和议价能力,提高农户养殖意识,鼓励发展新型养殖户等相关建议,希望使更多农户参与肉羊养殖产业,促进农户增产增收,推进环县肉羊产业现代化发展。