The CAMDAIRY model for formulating and analysing dairy cow rations

The paper describes a package of computer programs known as ‘CAMDAIRY’, which is written for CP/M80 and MS-DOS operating systems. The core program is a bio-mathematical model of a lactating cow, which incorporates functions to predict nutrient requirements, feed intake, substitution effects when feeding concentrates, tissue mobilisation and partition of nutrient utilisation between milk production and growth. Nutrient partitioning is described by a series of asymptotic curves relating energy intake to milk production, such that energy requirements per litre increase progressively with level of milk production. This model is incorporated into an econometric model, ‘Maximum Profit’, which uses linear programming procedures to formulate rations for up to two groups of cows in a herd in a way which maximises income above feed costs, whilst meeting nutrient requirements and satisfying constraints on feed supply and milk production requirements. Other programs in the CAMDAIRY package are ‘Least Cost’, a program which calculates a leastcost ration using fixed energy requirements for milk production, and ‘Analysis’, a program which predicts likely milk production given characteristics of the cows, feed intake and feed composition.     

Implications of on-farm segregation for valuable milk characteristics

Milk composition varies between herds and cows within herds, enabling its segregation on farm, rather than during processing, for the manufacture of specific dairy products. Benefits may include increased product yields, reduced processing costs and greater suitability of differentiated milk for the production of high value niche market products. However, costs are also likely to be greater. An integrated spreadsheet model was developed to determine the break-even premium required for a farmer with a seasonal calving herd to be economically no worse off producing segregated than conventional milk. The model incorporated breeding (quantitative and qualitative traits), cow requirements and feeding, transport, and economic sub-models. Cows were segregated within herd and milk composition was altered over time by genetic selection. Four quantitative trait (“white” milk colour) scenarios and two qualitative trait (BB β-lactoglobulin milk) scenarios were considered.The model suggested that “white” milkfat would need to earn 38.4% more at the farm gate than conventional milkfat for the two systems to break even. “White” milk cows produced less than their status quo counterparts due to the reduced selection pressure on production milk traits and this had a considerable impact on the premium, as did the low initial volumes of white milkfat. The difference in production between the B β-lactoglobulin cows and their status quo counterparts was less than for selection on white milkfat only. The high risk to farmers of discontinuing a differentiated milk policy could be moderated by changing the structure of premium payments over time. Hence, processing companies and farmers will need to work together to facilitate the uptake of milk segregation. This research model could be applied by dairy companies and farmers considering milk segregation policies.     

GAMEDE: A global activity model for evaluating the sustainability of dairy enterprises Part I – Whole-farm dynamic model

 Crop-livestock farms are complex systems. The interactions operating in such systems involve decisional, biophysical, structural, and environmental factors. Moreover, as farmers face a large range of management options, tools are needed to support their decision-making to enable them to reach production levels meeting their objectives and compatible with their human and physical resources, while controlling their effects on the environment. Gamede, a whole-dairy-farm model, has been developed to explore this complexity and to represent dynamically the effect of management decisions on biomass and nitrogen flows and on numerous sustainability indicators, such as milk and forage crop productivity, labour requirements, nitrogen balance, and nitrogen efficiency.This article describes the integration of six modules accounting for biophysical processes in a dairy farm (forage production; forage conditioning; herd demography; milk, excreta and animal biomass productions; grazing, quality of fertilisers; and nitrogen gaseous emissions) together with a decision system accounting for the farmer’s strategy and technical operations. Most of the six biophysical modules incorporate mathematical models from the literature, but the decision system stems from our own original work.Six commercial farms with different structures, agro-climatic conditions and management strategies were used for validation. The model can explain the differences found in their sustainability indicators at the year scale. The intra-year variability of the main biomass stocks and flows is also well explained. This quantitative validation was completed by a qualitative validation from researcher, adviser and farmer points of view, including simulations of prospective scenarios.     

A dynamic bio-economic model to simulate optimal adjustments of suckler cow farm management to production and market shocks in France

Tactical adjustments to seasonal weather conditions and beef price may generate additional income or avoid losses in French beef cattle farms. Due to the length of the suckler cow production cycle, adjustment decisions may impact not only on current production and profit but also on future farm outcomes. To better understand the consequences of shocks and subsequent production adjustments on the evolution of farm earnings and production over time, we built a dynamic recursive bio-economic farm model. Our model introduced simultaneously the possibility of adjusting herd size and herd composition, diet composition and diet energy content, as well as crop rotation, haymaking and feed stocks, taking into account both their short- and long-term consequences. An application is provided to test impacts of crop yield and beef price shocks of different intensities. Main simulated adjustments to face unfavourable weather shocks are (1) purchased feed in order to maintain animal production objectives, and (2) area of pasture harvested for haymaking. Very severe beef price shocks induce forced sales. Weather shocks affect farm net profit not only of the current year but also of the following years. Profit losses caused by unfavourable weather conditions are not compensated by gains in favourable ones and this differential is amplified when intensity of shocks rises.     

The promising impact of ley introduction and herd expansion on soil organic matter content in southern Mali

In southern Mali, cultivated area and herd size increase together with population growth. Consequently, periods of natural fallow shorten and traditional farming and animal husbandry techniques lead to a decrease of soil organic matter (SOM) content. Between 20 and 45% of the land is cultivated while less than 60% is arable area. To increase efficiency of natural fallow, a reduction in livestock herds is often proposed. By means of a linear programming model, the feasibility of maintaining actual SOM content in two villages in different agro-ecological zones was investigated. By adjusting animal numbers and cropping pattern, the model maximized: (1) SOM content under the condition of positive farm labour income; or (2) farm labour income under the condition of a positive SOM content. The model results suggested that maintaining SOM content requires the use of cereal crop residues for animal feed and for manure through bedding in kraals, but also higher animal densities. The last was feasible only through: (1) herding cattle of several farms together to overcome labour constraints; and (2) introducing P-fertilized leys, for grazing in the dry season. Grazing of the leys together with crop residues allowed animal densities up to 44 tropical livestock units (TLUs) km⁻², while less than 16% of the produced rangeland fodder was grazed. In such conditions, a positive SOM balance and higher income was obtained with a minimum of 16.7% of ley in the crop rotation. Limiting the area cropped with cotton stabilized income and contributed to a positive SOM balance. Zero-grazing during the warm season allowed SOM surpluses to be achieved with 12.5% of ley. However, as income decreased, seasonal zero-grazing could only be adopted for high-producing animals and small herds.     

Computer assisted management decisions for beef production systems

A linear programming model was developed to determine management policy for a yearly planning horizon on a typical 1320 acre (535 ha) Southern Colorado mountain ranch. Income producing activities (selling cattle and hay and leasing land) and cost activities (buying cattle, borrowing capital, feeding supplements, purchasing fertiliser and fuel, hiring labour and leasing land) were defined for three land types through four seasons.The purpose of the modelling effort was to determine the level of each activity (cow herd size, yearling herd size and area of meadow to be harvested for hay) that resulted in maximum net return for the ranch subject to resource limitation on land, labour and capital. In addition, sensitivity and shadow price analyses revealed expansion options that would be profitable during existing economic conditions.The optimal management plan, using 3 April, 1975 prices, called for grazing 199 head of 450 lb (204 kg) steers and 52 head of 530 lb (240 kg) steers. The plan also called for purchasing and spreading 42 tons (38 MT) of nitrogen and 10 tons (9 MT) of phosphorus on Land I and for growing, harvesting and selling 742 tons (674 MT) of hay. This optimal management plan produced a net return of $27,642. In addition, the optimal plan showed that hay production began replacing beef production when the price of hay was $35·48/ton (39·08/MT) and that the maximum amount of hay was produced with the price increased to $50·00/ton ($55·00/MT).     

Financial implications of recent declines in reproduction and survival of Holstein-Friesian cows in spring-calving Irish dairy herds

Milk production and reproductive performance were monitored in 14 spring calving dairy herds in the south of Ireland between 1990 and 2003. In these herds, the average pedigree index for milk yield increased by 25 kg per year from 1990 to 2001, while the average proportion of Holstein-Friesian genes in the cows increased from 8% in 1990 to 63% in 2001. Over this period, milk production per cow increased by 54 kg/year, while replacement rate increased from 16% in 1990 to 27% in 2003. To evaluate the farm-level financial implications of associated changes in calving pattern, milk production and replacement rate, data from the 14 spring-calving herds were included in the Moorepark Dairy System Model for each of the 14 years. Two milk production scenarios were investigated, which included EU milk quota applied at farm level (S1) and no milk quota (S2). The influence of variation in milk price, cull cow value, replacement heifer cost and replacement rate were modelled using stochastic budgeting. In S1 there was a significant linear increase (P < 0.05) in margin per cow (€10.8), margin per kg of milk produced (0.13 cent) and net farm profit (€546) over the 14-year period. Similarly in S2 there was a significant linear increase in margin/cow (€11.3), margin/kg (0.14 cent) and farm profit (€1089) over the 14-year period. However, the analysis showed that if reproductive performance, calving spread and replacement rate could have been maintained at 1990 levels for each of the 14 years then the increase per cow, per kg of milk and farm profit per year would have been €22.1, 0.31 cent and €1341 for S1, and €22.8, 0.32 cent and €2183 for S2, respectively. Stochastic analysis showed that farm profit was most sensitive to changes in milk price, followed by replacement rate.     

A preliminary model to investigate culling and replacement policy in dairy herds

Replacement policy in dairy herds is not easy to determine when heifers are both home-reared and compete for land with the cows. The difficulty lies in evaluating quantitatively the advantages and disadvantages of low and high replacement rates. A computer simulation model was developed to examine the effects of different replacement rates on genetic improvement in yield per cow, milk output and farm profit at two levels of culling for reasons other than insufficient yield.The working hypothesis suggested by the results is that profitability falls as replacement rate increases because the number of cows able to be milked and the maturity of the herd over-ride the gains in milk yield per cow due to genetic improvement by yield culling and the greater use of a sire of high genetic merit.     

Simulating differences in net returns from beef production under alternative forage systems and management practices

A biological simulation model and a linear programming model were interfaced to determine production efficiencies and the optimal carrying capacity of a cow-calf producer in East Texas and to compare net returns to the model farm, given alternative tame forage systems and management practices. Experimental data both on forage systems and on livestock were used to verify and validate the simulated herds. The results showed that (1) of the three tame forage systems analyzed, warm-season perennial forages provided a relatively higher carrying capacity/ha, whereas a mix of both warm- and cool-season forages that allows year-round grazing gave relatively higher net returns/ha to management; (2) nutritional stress during winter months decreased animal performance proportionately more than it decreased feed costs; and (3) although spring-calving herds included more animals than corresponding fall-calving herds on the same land area, fall-calving herds produced more liveweight sales and generally higher net returns.     

Smallholder dairy production and markets: A comparison of production systems in Zambia,Kenya and Sri Lanka

Three smallholder dairy production systems in Zambia, Sri Lanka and Kenya are analysed and compared. The focus is on the relationships between the animal production system, the farm household system, and the institutional environment. Attention is given to the valuation of marketed and non-marketed products and the intangible benefits of livestock in insurance, financing and status display. The comprehensive and comparative analysis of the production systems shows the direct relationship between type and intensity of dairy production and the presence or absence of markets for milk and other products, services and employment. The generally unobserved income components resulting from products other than milk and from the intangible benefits prove to be a substantial proportion of the total income in all three systems. The comprehensive perspective on the dairy production system results in policy suggestions that include institutional linkages.     

畜牧机械生产企业及其对农民收入影响的分析

对我国畜牧机械生产企业按地区、省份的分布情况以及农民收入的情报发布进行了统计分析，旨在发现畜牧机械生产企业的分布规律厦其与当地农民收入的关系。华北、东北以厦西北等经济发达地区或欠发达地区，畜牧机械生产企业多数围绕于省会等中心城市而发展，说明中心城市对这一行业的主导作用；华东以及东南沿海的经济发达地区，较多的畜牧机械企业围绕中小城市分布，表明了当地经济发展与畜牧机械生产的紧密相关性。无论中心城市分布型或中小城市分布型，畜牧机械企业的存在对当地农民收入的影响呈现正相关关系。发展畜牧机械生产企业，是实现农民增收、农业增效和可持续发展目标的重要步骤。     

Pasture and forage crop systems for non-irrigated dairy farms in southern Australia. 1. Physical production and economic performance

The dairy industry in southern Australia relies on perennial ryegrass pasture to supply 60–70% of the diet of lactating cows. Improvements in the amount and quality of home-grown forage used for dairy cow feeding are critical for further productivity gains in the industry. A modeling approach was used to estimate the effects of changing the forage system on farm business profit. Base models (using 100% of farm area in perennial ryegrass pasture) were constructed for above-average (Top 40%) and high performing (Top 10%) farm types typical of two locations: Terang in southwest Victoria and Ellinbank in Gippsland, eastern Victoria. These models were then re-simulated using different forage base options such as: oversowing annual ryegrass, winter crops (annual ryegrass monoculture, winter cereal grown for whole crop silage), summer crops (grazing brassicas, maize), combinations of these (double cropping), or summer shoulder pasture (notionally based on tall fescue) on between 10% and 100% of farm area.     

A bio-economic model of small-ruminant production in the semi-arid tropics of the Northeast region of Brazil: Part 2—Linear programming applications and results

Survey data covering production systems for mixed farms in the Northeast region of Brazil has been synthesized within a linear programming (LP) framework. The resulting model contains activities covering the production of cattle, sheep and goats, and a vector of alternative cropping activities. Farm resources include two categories of grazing land, planted forages, family labour, two categories of hired labour, and working capital. The major livestock activities represented in the region were included as production options.Initial results did not discriminate between categories of available grazing resources. Therefore, cattle, by virtue of their higher dressing percentages and higher price per kilogram, were the optimal livestock species. A series of adjustments was then carried out to reflect types of feed resources and patterns of animal species selectivity. Optimal farm solutions for a representative traditional-production unit found objective function levels close to those found by farm surveys, but discrepancies between model results and the actual farm situations for sheep and goat activities. Model results excluded small-ruminant breeding activities because of the low net offtake at weaning levels assumed in the model. Data that became available after these initial model runs showed a higher net offtake level, and these revised coefficients resulted in optimal LP results very close to those actually found on farms.The model was then used to simulate the response of activities and farm economic performance to ‘good’ and ‘bad’ years defined by ± half standard deviation from mean annual levels of precipitation. Model results indicated much higher variability of farm income in response to weather than that found with changes in levels of technical efficiency of sheep and goat production.     

A systems approach to quantify greenhouse gas fluxes from pastoral dairy production as affected by management regime

A model was developed to determine what effect management practices would have on the production of the greenhouse gases (GHG) within pastorally based dairy production systems typical of those practiced in Ireland. The model simulates two levels of GHG emissions, firstly the on-farm GHG emissions of methane, nitrous oxide and carbon dioxide for example from the pastorally spreading of slurry and secondly, off-farm GHG emissions associated with both inputs brought onto the farm to maintain productivity (for example emissions arising from manufacture of concentrate feeds and fertiliser) as well as from indirect GHG emissions associated with nitrate leaching and ammonia. The aim of this work was to allow the development of effective GHG mitigation strategies at the farm level capable of reducing GHG emissions per litre of milk.Greenhouse gas emissions were modelled for nine farming systems differing in the level of concentrate supplementation (376, 810 and 1540 kg per cow per lactation) and genotype for milk production as assessed by their pedigree index (<100, 100–200 and 200–300 kg) of milk production. A three-year study to evaluate the influence of cow genetic potential for milk production and concentrate supplementation level on profitability of pasture-based systems of milk production was used to drive the Moorepark Dairy Systems Model (MDSM). Output from this model then described farm size, feed budgets, animal numbers and farm profitability when annual milk quota was set to 468,000 kg of milk year. Relating GHG emissions to annual milk sales revealed that for these pastorally based systems increasing concentrate usage reduced both on-farm and off-farm emissions, but that increasing the genotype of the dairy cow (i.e., the genetic capacity of the animal to produce milk) will increase both on-farm and off-farm GHG emissions. Lowest GHG emissions per kilogram of milk were achieved for an intermediate genotype type cow fed within a high concentrate system whilst the highest emissions were associated with high genotype cows fed within a low concentrate system. Maximum profitability was obtained when either a high concentrate feeding regime was combined with high genotype cows or where low concentrate systems were fed to low genotype cows.Relating farm profitability to GHG emissions allowed the identification of scenarios where changing from one management systems to another would achieve a simultaneous reduction in GHG emissions whilst improving farm profitability. By implementing this approach of assessing management induced change on both GHG emissions arising from the farm together with farm profitability, individual whole farm GHG mitigation strategies could be developed with a high degree of acceptability to the producer.     

基于牧草压缩特性的凸轮式牧草压捆机设计

牧草是发展畜牧业的基础,但由于其地理分布和自身松散的特性,导致牧草储运成本过高,通常需要对牧草进行压缩打捆处理。牧草压缩过程中预压缩阶段位移大压力小,致密阶段位移小压力大,压缩过程中牧草的压缩特性不断变化。为此,设计了一凸轮式牧草压捆机,利用凸轮能够实现复杂运动的特点,使牧草在压缩过程中进行变速压缩,符合压缩特性曲线的变化规律。通过Pro/E软件对整机进行干涉检测以及运动学仿真模拟,结果表明:该机构可以实现快速进行预压缩、慢速进行压紧阶段的压缩,进而提高牧草压缩效率并达到降低能耗的目的。     

The impact of increasing farm size and mechanization on rural income and rice production in Zhejiang province,China

Economic growth in China’s agricultural sector lags behind growth in industry and services, creating an ever widening rural–urban income gap. Development of the non-agricultural sectors offers new opportunities for farmers in China’s more advanced provinces such as Zhejiang. Increased income in the urban sector creates markets for new products, and migrating farmers rent their land to those staying. Until now, the prevailing rice-based systems have been managed mainly using manual labour and animal traction, but the larger farms resulting from migration may facilitate, or even require mechanization. In this study, we use a simulation model of the farm household to analyse the effects of increasing farm size and the transition from rice to vegetable production, while also studying the effects of mechanization.     

Simulated comparisons of breeding plans for beef production—Part 1: A dynamic model to evaluate the effect of mating plan on herd age structure and productivity

A computer program to simulate beef production is described. The model is based on the principles of industrial dynamics and constructed in the simulation language DYNAMO. This dynamic model is composed of subroutines that simulate herd structure for a cow herd and a production herd composed of calves from the cow herd. Additional subroutines model pre-weaning and post-weaning growth of the calves.The portion of the model that simulates the herd structure includes ten age classes of cow. The subroutine which models the portion of the herd between 2 and 9 years of age utilises twelve variables to describe the events that occur in the herd during the passage of a year. The age structure of the herd is influenced by the breeding system and the way in which the herd is managed.The production herd is modelled by sequential subroutines. These subroutines follow the number and growth of calves weaned from the cow herd until they are sold at 32, 52, 67 or 85 weeks of age. Mating plans utilising different breeds can be simulated in combination with various management options.     

Characterising rice-based farming systems to identify opportunities for adopting water efficient cultivation methods in Tamil Nadu, India

Efficient water use in rice cultivation is a prerequisite for sustaining food security for the rice consuming population of India. Novel rice production practices, including water-saving techniques, modifications in transplanting, spacing, weeding and nutrient management, have been developed and shown to be effective on farm, but adoption of these techniques by farmers has remained restricted. Potential constraints include technical difficulties with new practices, and labour and gender issues which differ between farms. On the basis of a rapid survey of 100 rice-based farms, four farm types were identified based on their socio-economic and biophysical characteristics. Detailed farm surveys were conducted on three representative farms of each farm type to evaluate land use patterns, use of inputs such as water, labour, nutrient, capital and machinery, income from crop and animal production and off-farm activities. Opportunities exist for one or more new rice cultivation techniques to be adopted in all the four farm types. For all farm types, however, the opportunities for use of water-saving irrigation were the least promising. In general, adoption of water-saving irrigation will not improve farmers’ livelihoods despite its importance in reducing water scarcity problems at regional scale. At farm scale, the potential for adoption of water-saving irrigation depends on the season, location of fields and the irrigation source. Changes in government policies such as rules and regulations, pricing, institution building and infrastructure development, as well as training and education of farmers are needed to improve the adoption of modified methods for rice cultivation.     

Evaluating crop-livestock-based farming systems: A village level study in the dry zone rainfed district of Sri Lanka

In Sri Lanka cropping enterprises interact with livestock production on peasant farms. This analysis of the crop-livestock farming system aims at understanding the existing constraints and interactions between crops and livestock in these farms. The main objective of the study is to describe the crop-livestock integrated farming systems in three rainfed villages in the Moneragala district of Sri Lanka, and to evaluate these systems in terms of maximizing farm incomes from the different crop and livestock components of the systems. A field survey was conducted to collect data from 153 farming families for the Maha season of 1982/83. A linear programming model was formulated to test the hypothesis.The results show that in general the activities for lowland rice, highland rice, sugar cane, labour, farm cash cost, and MVP (compost) are higher in the optimal farm plan than in the actual farm situation. The livestock in the optimal plan is mainly confined to milch cattle. However, with the present high level of manutrition among rural livestock industry emphasis should be placed on the expansion of the rural livestock industry in the study villages. The optimal plan also suggests the use of crop residues as a substitute for compost for farm crops. Hence, in the context of escalating prices of chemical fertilizers, research is required to find the suitability of crop residues and household residues as substitutes for compost. Increases in supplementary irrigation may result in the expansion of the farm area and hence the farm income. Other methods of increasing farm income include: replacing hired labour with non-utilized family labour, increased agricultural research, and extension activity regarding the use of modern inputs by farmers on crops.