Profit in a pig herd from performance testing and selection of breeding stock. The effect of variation in the accuracy and cost of testing

Computer modelling was used to compare a variety of performance testing and selection programmes whose objective was to increase the monetary value of pigs as determined by their rate and efficiency of growth and the leanness of their carcases.Factors varied over feasible ranges were the cost and accuracy of performance testing, the culling rates of breeding stock and the degree of subdivision of the herd into a nucleus supplying breeder replacements for the whole herd and a production unit producing slaughter stock.Net returns per sow, evaluated over 10 years of selection, increased, by 120 times, the standard deviation (sd) of the breeding objective for each improvement of 0·1 in the correlation between the selection criterion and the breeding objective (test accuracy).A unit of the cost of testing each pig equalled 0·4 sd of the breeding objective and net returns in the unsubdivided herd declined by 0·6 for each unit increase in cost. Herd subdivision increased net returns by reducing the number of pigs tested—and hence the cost of testing. The optimum ratios of production unit to breeding nucleus sizes which maximised net returns were found. When herds were subdivided in an optimum way, the decline in net returns with increasing testing costs was reduced sixfold.Returns were highest when boars were worked for only one breeding cycle (approximately 6 months) in both the nucleus and the production unit. Depending on the accuracy and cost of testing, maximum net returns occurred when nucleus sows were culled after one or two farrowings. Sows in the production unit were an optimum combination of culled ‘old’ sows and selected ‘young’ gilts from the nucleus. There were a number of other replacement schemes which were almost equally profitable.     

A simulation model of a breeding ewe flock

A simulation model was constructed of a self-replacing flock of Merino ewes grazing a predominantly Wimmera ryegrass and subterranean clover pasture in the Eppalock catchment of northern Victoria, Australia. The model was used to predict the likely physical, biological and economic consequences of changes in stocking rate and date of lambing.Routines for simulating the local climate, together with expected levels of pasture production, were based on available local data. The herbage produced was utilised for animal maintenance, growth, pregnancy, lactation and wool production. Predictions were made of the ovulation and fertilisation rates of the breeding ewes and the subsequent survival of embryos and lambs. Lamb growth rates were determined relative to their predicted intake levels of milk and herbage.The economic consequences of different combinations of ewe stocking rate and date of lambing were evaluated by simulating the cash flow of the property. Financial returns were obtained from the sale of wool, cast-for-age and culled ewes, and wether lambs.     

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.     

Differences in sheep production between sites within a heterogeneous area

Two stocking rate experiments were performed within an area of 160 ha with (a) weaners (randomised blocks) and (b) breeding ewes (completely randomised design). Using a quadratic economic objective function to combine outputs of wool, lambs, etc., the range of estimates of optimum stocking rates was, for weaners, from 9 to more than 25 per hectare and, for ewes 8 to 20 per hectare. Analyses of variance showed that residual errors were large compared with the effects of stocking rate, management and years. Where attributes of production were relatively accurately measured and sampled, the between site-within stocking rate variance accounted for approximately 75% of the total residual error.Differences in soil depth, aspect, slope, soil moisture and nutrient characteristics are suggested as the fundamental causes of these block differences. However, the few comparisons available did not permit further analysis. Possible benefits to both farm management and experimentation from predicting site potential from these parameters are discussed.     

Estimation of optimal stocking rate of merino sheep

The evaluation of wool by objective measurement means that decreases in fleece weight, such as those caused by higher stocking rates, may be wholly or partly compensated for in value by increased prices for wool of reduced fibre diameter. This paper examines the effect of such compensations on the marginal returns to increased stocking rates.Two approaches were used. First, the effect of stocking rate on gross margins was examined over a given distribution of seasons so as to determine the most profitable stocking rate. Secondly, the cash flow of a wool-producing enterprise was examined over a random sequence of years. The most profitable stocking rate was increased by objective evaluation by about 12% if a decrease in fibre diameter of one micron were associated with an increase in wool price of 10 cents per kilogramme, using fleece weight-stocking rate relationships derived from field experiments.Inventory analyses were used to examine the long-term relationships between stocking rate, financial stability and profitability. For each stocking rate studied, the cash flow and mean and minimum bank balances of a farmer were simulated over a set number of years. The stocking rate at which the highest minimum bank balance was recorded was about 15% (one to two wethers per hectare) lower than that at which the standard of living and the mean bank balance were at a maximum. That is, a risk-avoidance policy would not differ greatly from a profit-maximisation policy with respect to stocking rate.     

基于均值回复的实物期权战略投资分析

古典的Black-Scholes期权定价模型认为资产回报服从几何布朗运动,但实证分析证明至少有三种形式有别于该基准假设,如价格跳跃导致的非正态分布、回报方差的时变性及均值与方差的相关性。价格回报过程的假设对期权定价乃至项目价值估价至关重要,本文提出当资产价格服从均值回复过程时的实物期权战略投资时机分析,并与几何布朗运动假设条件下的结论进行了比较。     

Returns from small ruminant production in South West Nigeria

Dwarf goats and sheep are ubiquitous in the humid zone of West Africa, although only as a supplement to cash and food crop production. This paper presents estimates of the returns obtained from these small ruminants under traditional production systems. Returns are, on average, high, but variable, especially in view of disease risks. Apart from disease control measures to reduce mortality, improved nutrition is needed for intensifying production. At current levels of management neither pasture production nor housing and hand-feeding are likely to yield increased returns. Alley farming, a system of intercropping with shrub species and the feeding of shrub trimmings to small ruminants, seems a promising alternative.     

Pasture and forage crop systems for non-irrigated dairy farms in southern Australia: 3. Estimated economic value of additional home-grown feed

Dairy systems in southern Australia rely on grazed feed from pasture to supply between 50% and 70% of total herd feed requirements on an annual basis. However, the dominant pasture type in the region, which is based on perennial ryegrass (Lolium perenne), commonly results in feed deficits in summer which must be filled with supplements purchased off-farm, and feed surpluses in spring which must be conserved. Both of these strictures impose costs on farm businesses. It is likely, therefore, that additional grazeable feed available to dairy herds in southern Australia may have different economic value when interactions between season, stocking rate, calving date, and locality are taken into account. The analysis reported in this paper aimed to estimate, using the farm systems simulation model UDDER, the effect of these interactions on the efficiency with which extra feed can be converted to extra milk production, and therefore the possible gross economic value of the additional feed.‘Base’ farm simulations for ‘average’ and ‘top 10%’ farms (ranked according to farm profitability) in two localities (Terang: average annual rainfall 796 mm, 8 month growing season; and Ellinbank: average annual rainfall 1085 mm, 9-10 month growing season) were created to mimic the physical production and profitability of these farms as seen in regional farm benchmark datasets. These simulations were then altered to add the equivalent of 10% of the total annual herbage accumulation used in the Base simulation either on a pro-rata basis all year round, or in autumn only, in winter only, in spring only, or in summer only. The additional feed amounted to 620 and 780 kg DM/ha for Terang average and top 10% farms respectively, and 735 and 905 kg DM/ha for Ellinbank average and top 10% farms respectively. The management policies used in the Base simulations were then adjusted to harvest as much of the extra feed as possible, either by direct grazing or through silage conservation, while keeping the key system state indicators of cow condition score and average farm pasture cover within the limits known to result in long-term sustainable production.The efficiency with which extra feed was utilised was greatest in summer in all scenarios (80-100% of the extra feed supplied was harvested, all by direct grazing). This translated into consistently high gross economic returns of between $0.26 and $0.34 per kg DM of extra feed added to the model. Utilisation efficiency was lower in all other seasons and/or required marked increases in silage conservation, both of which resulted in lower gross economic returns per kg DM of additional feed. The impact of interactions between locality, season, stocking rate (higher in top 10% farm simulations than average farm simulations) and calving date (earlier at Terang than at Ellinbank) were clearly captured in the model. These interactions have very large effects on the profitability of growing extra feed at different times of the year. Agronomic research for the southern Australia dairy industry should focus on low-cost ways for supplying additional grazeable feed in summer, since current forage species options for this time of year are limited.     

Effect of changing energy prices on commodity prices and farm income

Tatonnement programming is used to examine the effect of energy prices on commodity prices and farm income. This method uses a national interregional linear programming model in conjunction with demand equations for feedgrains, soybeans and wheat. This spatial programming model is solved iteratively with these demand functions using an algorithm based upon the Walrasian tatonnement process. While the model is static in nature, it indicates that once adjustment to a doubling of energy prices occurs returns to land will increase by 10·8%. Commodity prices will increase 24·1, 18·7 and 9·9% for feedgrains, wheat and soybean, respectively, and demand will decrease 2·2, 1·9, and 0·9% for these same three commodities.     

Financial analysis of wine grape production using regulated deficit irrigation and partial-root zone drying strategies

Cost-benefit analysis was performed to determine the profitability of producing wine grapes under different irrigation regimes. Vines irrigated by regulated deficit irrigation (RDI) and partial root-zone drying (PRD) were compared with vines grown under full irrigation in a typical vineyard in a semiarid environment with scarce water resources (south-eastern Spain) during three consecutive years. Five irrigation treatments were applied. The Control treatment irrigated at 60% of the ETc (Crop evapotranspiration) throughout the orchard cycle. PRD-1 and RDI-1 provided deficit irrigation from fruit set to harvest (irrigated 30% ETc) and post-harvest (45% ETc). PRD-2 and RDI-2 provided deficit irrigation from fruit set to harvest (irrigated 15% ETc) and post-harvest (45% ETc). From an economic point of view, only the Control, PRD-1 and RDI-1 treatments were economically viable since their profitability indicators were positive, although low, especially PRD-1. The more severe deficit irrigated treatments (PRD-2 and RDI-2) were unviable. The most profitable treatment was the Control which had a Net Margin/total cost ratio (NM/C) (representing the overall profitability of the vineyard) of 25.37% compared with the 1.90% of RDI-1 and 0.57% of PRD-1. The threshold price of water indicates that only the Control remains profitable with higher water prices of up to 0.46 € m⁻³. When the cost-benefit analysis took into account the extra quality achieved in PRD-2 and RDI-2, it indicated that these treatments, which were otherwise economically unviable, achieved high returns (17 and 16%, respectively) and were close to the Control treatment. Thus, a low or moderate bonus that encourages extra berry quality for premium wine production would make deficit irrigation practices profitable. Moreover, the financial indices estimated suggest that in the present situation, and with our soil and climatic conditions, PRD is less economically profitable (higher installation cost, lower NM/C, and threshold price of water) than RDI under the same conditions.     

Pressure Drop Through Wheat as Affected by Air Velocity,Moisture Content and Fines

Pressure drops were measured in clean wheat beds for superficial air velocities up to 0·42 m/s at grain moisture contents in the range of 12·8–22·3% w.b. At 12·8% moisture content, pressure drops were determined in wheat for fines contents up to 10·60% (w/w). It was found that pressure drops decreased by up to 30% with moisture content and increased with fines by up to 75%. The selection of a model was made using the results of clean grain. A Shedd-type equation (model 1), the Hukill & Ives’ equation (model 2), and an Ergun-type equation (model 3), all of two parameters, were examined. Model 3 behaved better than model 2 and both gave lower errors than model 1. Model 3 was simplified by considering the parameter of the quadratic term as a multiplier of that of the linear term. The resultant expression (model 4) behaved better than model 2 and was called the approximate, Ergun-type equation. With this model, the non-linear influence of grain moisture content was better predicted than with a linear model proposed previously. With regard to the effect of fines, the use of model 4 permitted a linear relationship between pressure drop ratio and fines content that was independent of air velocity, a feature that was substantially adequate to describe the experimental results. Model 4 is suggested for further work on the resistance to airflow of grain beds.     

The economics of low pressure drip irrigation and hand watering for vegetable production in the Sahel

Low pressure drip irrigation is being promoted in Sub Saharan Africa as an alternative to traditional methods of small scale irrigation of vegetables. The African Market Garden (AMG) is a horticultural production system for smallholders based on low-pressure drip irrigation combined with an improved crop management package. The agronomic and economic performance of the AMG is compared to two gardens irrigated manually with watering cans. One of these gardens is managed according to the same improved crop management package as in the AMG, this treatment is called Improved Management (IM). The other garden is managed according to common practices of vegetable producers in the area, this treatment is called the Farmer Practice (FP). Crop productivity, labor and water use were monitored for two vegetable species (okra and eggplants). The experiment was performed on-station in Niger on three adjacent 500 m² plots in a sandy acid soil. It was found that improved crop management practices greatly enhance crop productivity over traditional methods at comparable production costs. The AMG gave higher crop yields and higher returns to investment than the treatments irrigated with watering cans. Labor accounts for up to 45% of the production cost in vegetable gardens irrigated by hand, where 80% of the producer time is spent on irrigation. The total labor requirement for the drip irrigated AMG was on average 1.1 man hours per day against 4.7 man hours per day for the Farmers Practice on a 500 m² garden. Returns on labor are at least double for the AMG against the other treatments. The returns on land from eggplant were found to be US$ 1.7, 0.8 and 0.1 per m² for the AMG, IM and FP respectively. The returns on water for the cultivation of eggplant are around US$ 2 per m³ in the AMG, against US$ 0.1 in the Farmers Practice. This experiment showed the strong positive impact of drip irrigation and improved crop management practices on profits at minimal environmental costs, indicating that transformation of existing practices poses a considerable potential towards sustainable agricultural development.     

调水工程两部制水价风险分析

两部制水价能有效降低调水工程的经营风险,但也存在不安全因素。本文阐述了两部制水价实施过程中的风险来源;根据两部制水价的结构特征,提出利用总亏损率、短期亏损率、水价超额率以及总风险度来度量不同基本水量方案的风险程度。在核算供水成本的基础上,计算了在实际供水量不足的情况下,三种水价方案的风险程度,得出胶东调水工程的基本水量不宜超过设计供水量的20%的结论,并通过灵敏度分析证明该方案具有一定的抗风险能力。     

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.     

The evolution of smallholder irrigation policy in Zimbabwe: 1928–1986

Voluntary smallholder irrigation schemes in Zimbabwe were launched in 1913 as a means of famine relief and subsequently to settle black farmers displaced from designated areas for white commercial farmers. In 1928 the colonial government inaugurated a programme to provide services to existing smallholder schemes and to assist in developing new schemes. This process eventually led to the erosion of farmer participation in planning, development and financing of smallholder schemes. Since 1928 the smallholder schemes have been heavily subsidised, a pattern that continues today. Currently about 3.4% of the land under irrigation is farmed by small holders who pay about 11% of the costs of irrigation operation and maintenance; the remaining 89% is subsidised by the government. More smallholder irrigation development is currently being planned. The government has made loan funds available to groups on the basis of financial viability, but to date this fund has not been significantly utilized by smallholders. In essence, smallholder irrigation development is being constrained by problems that have plagued smallholder schemes since 1928.Abbreviations AGRITEX Agricultural Technical and Extension Services - ARDA Agricultural and Rural Development Authority - DERUDE Department of Rural Development - NFIF National Farm Irrigation Fund - Z$ Zimbabwe Dollar     

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。     

甘肃省环县农户肉羊养殖意愿影响因素分析

基于甘肃省环县5个乡镇的调研数据，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。提出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、提高农户养殖意识和鼓励发展新型养殖户等建议，希望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。      

Water use and technical efficiencies in horticultural greenhouses in Tunisia

We measure the technical efficiency of unheated greenhouse farms in Tunisia, and propose a measure for irrigation water use efficiency (IWUE) using an alternative form of the data envelopment analysis (DEA) model. Technical efficiency measures the degree to which (all) farm inputs are used efficiently. IWUE is a measure of the efficiency of irrigation water use when other inputs and output are kept constant. As a second stage, a tobit model is used to identify the degree to which technical efficiency and IWUE correlate with a set of explanatory variables. A comparison of the efficiency scores obtained from constant returns to scale (CRS) and variable returns to scale (VRS) specifications shows that most farmers in our sample are producing at an efficient scale. Under the CRS assumption, the average technical efficiency of the sample was 67.3%. A similar pattern of scores was shown for IWUE; although in this case the average IWUE was even lower (42%). This implies that when all other inputs remain constant, the current output could be produced using, on average, 58% less irrigation water. We conclude that farmers’ technical training in greenhouse management, investments in water saving technologies and the existence of a fertigation technique on farm have a significant and positive effect on their level of IWUE. However, IWUE is significantly and negatively affected by the proportion of total farm land allocated to greenhouses.     

Dynamics of plant and animal production of a subterranean clover pasture grazed by sheep: Part 1—Field measurements for model calibration

A grazing system with Merino sheep and subterranean clover pasture was studied in a 550 mm rainfall, mediterranean climate in Western Australia.Changes over twelve months in seed, the quantities of green and dry herbage, soil moisture, animal intake and liveweight, wool growth and body composition were measured. Six paddocks, representing two soil types, were grazed continuously at 8·75 sheep per hectare. The system was also simulated and the actual results were compared with those from the simulation model.From a seed pool in March of 300 kg ha^?1, 80% of which was soft and non-dormant, 4000 clover seedlings per square metre became established; subsequent drought reduced this to 1450 plants per square metre. From measurements of soil moisture it was shown that this population survived at available moisture levels as low as 0·5 mm in the main root zone in gravelly sandy loam. Pasture growth rate reached a spring peak of 102 kg ha^?1 day^?1 and total growth (estimated from pasture grazed for 26 weeks) was 6700 kg ha^?1 for 500 mm of rainfall between germination and maximum biomass. At maturity, burr and seed made up 57% of the plant residues on offer, with a seed pool of 1160 kg ha^?1. During the summer this biomass decreased at 5 kg ha^?1 day^?1 without grazing and 19 kg ha^?1 day^?1 under grazing.The liveweight losses and gains of the sheep were atypical, no liveweight gain until 1200 kg ha^?1 of gree herbage was available—about treble the expected amount. Measurements of food intake indicate a gross inefficiency in energy utilisation during the winter and a low intake of energy in the spring.Total green and dry plant residues showed general agreement between actual and simulated results for most of the growing season. However, the field data highlighted error in the pasture sub-model which were corrected and are reported elsewhere.