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1.
《Agricultural Systems》2005,85(1):82-97
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. 相似文献
2.
J.A.M. van Arendonk 《Agricultural Systems》1985,16(3):157-189
A model was constructed and validated to determine the course of performance, revenues and costs of dairy cows with different levels of milk production and of number of days open. For each month in lactation the revenues from milk production, which are dependent on the fat and protein contents, were determined. The feed costs were calculated from consumption of roughage and concentrate, which were estimated from the energy requirements. Furthermore, the course of the carcass value, calf revenues and the probability of, and the financial loss associated with, involuntary disposal were considered. Seasonal variation in production and prices was included in the model.Parameters of, and prices in, the model were chosen to represent the Black and White cows in The Netherlands at the normalized price level of 1981–1982.In the future the model will be used in studies on replacement policies in dairy cattle. 相似文献
3.
4.
《Agricultural Systems》1986,20(1):53-81
The further development and use of a bio-economic model to simulate small-scale dairy enterprises in South-East Brazil are reported.The account of animal nutrition has been refined to take account of protein requirements in addition to energy balance. A new version has been developed which allows for the inheritance of production traits.The model has been used to analyse the effects of short-term management decisions on feeding strategies and longer term breeding policies for herd development. It has been used, also, to examine the possibilities of culling for reproductive performance and the effects of a range of growth rates of replacement heifers on overall herd performance. 相似文献
5.
A dynamic stochastic model to simulate the reproductive process in a herd of dairy cattle has been constructed. The next event scheduling approach was utilized with four events being specified: perturition, ovulation, embryonic loss and replacement.The control variables included in the model are first breeding policy (1BDG), reproductive culling policy (RCLG), heat detection program (HDPM), breeding program (BDPM) and service sires selection program (SSPM). In addition, the model uses numerous endogenous variables such as parturition type (PRTY), oestrus behaviour (EBHV), cow's fertility (CFTY), embryonic mortality (EBLS), non-reproductive culling rate (NRCL) and others.The model was evaluated against independent experimental results. The simulated result closely approximates the average reproductive performance and variability of reproductive performance in a dairy herd. 相似文献
6.
A computerised model to describe and predict cattle production for any herd size and time period and for a wide range of environments, was developed from a model published by Sanders & Cartwright (1979a, b).The dynamics of the model are based on the flow of energy from vegetative sources to animal products in a single-animal or cow-calf unit, so that the model is appropriate even for smallholder herds. A separate flow of numbers records the dynamically changing herd size and structure.Reproduction and mortality are linked to the nutritional and physiological status of each individual. Their occurrence is triggered stochastically to preserve the integer quality of the herd. In all other respects the model is deterministic.The simulated herd can be of any number, breed, sex and age composition. Breeds are distinguished by mature size, growth rate and milk production: they can be single, dual and/or triple purpose (dairy and/or beef and/or draught). Feeding management can be grazing, stall-feeding or a combination of the two. Routines are included which can simulate different types of management decisions and their repercussions. Functions for the quantification of the model were selected according to preset guidelines, generally following an investigation of conflicting hypotheses.There are eight different output options (tabular and graphical), representing various levels of model resolution. 相似文献
7.
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. 相似文献
8.
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. 相似文献
9.
奶牛发情行为的检测研究 总被引：1，自引：0，他引：1
在奶牛养殖中,为增加牛奶产量,使奶牛及时受孕、产犊并提高泌乳期是非常重要的,而要达到上述目的,正确、高效地预测以及检测奶牛的发情期,并适时配种尤为关键。因此,奶牛发情的及时和准确识别则变得举足轻重,在牛群管理中具有重要地位。传统的奶牛发情检测方法愈加不能满足现代化奶牛养殖场的需求,基于微机系统的自动化电子检测技术迫切需要应用到奶牛发情检测中。对奶牛的发情行为的影响因素、传统检测方法以及数字化的检测方法进行了阐述,并对其数字化检测趋势进行了系统深入的探讨。 相似文献
10.
Peter Chudleigh 《Agricultural Systems》1977,2(1):67-82
A model of a smallholder dairying system in the high potential country in Kenya is briefly described. A sensitivity analysis was carried out with the model for two replacement policies and six herd sizes. The ensuing output of mean monthly milk yields and incomes was subjected to an analysis of variance where the major effects of four performance variables were ascertained. Response surfaces were fitted to the data generated from the model and were used to demonstrate that the relative income responses to an improvement in each variable dependend on the initial levels of performance.It is suggested that the technique reported here may be utilised as part of a larger cost-benefit analysis designed to assist in the allocation of resources for research and development aimed at improving the performance of smallholder dairy farmers. In addition, there is a need for greater involvement in extension research, so that the cost of obtaining an improvement at the farm level in a given performance variable can be estimated. Guidance of research and development priorities with respect to the smallholder dairy industry could then proceed in a more rational manner. 相似文献
11.
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. 相似文献
12.
K. Bartl A.C. Mayer C.A. Gmez E. Muoz H.D. Hess F. Holmann 《Agricultural Systems》2009,101(3):152-161
In four communities in the Peruvian Andes, 56 farmers were interviewed every three months over a period of one year. Information linked to milk and cattle production such as activities, inputs (labour, means of production, capital) and outputs (milk, cheese, animals) were recorded using a closed-ended questionnaire. The communities were divided into two groups with low (LC) and high (HC) level of dependence on income from milk and animal sales. The survey results showed that cattle production on the LC farms was based on less land and a smaller herd (3.32 ha/farm, 1.06 lactating cows) than on HC farms (10.28 ha/farm, 4.19 lactating cows). The data from the survey and the results of the nutritional analyses of 74 feed samples were introduced into a model that applied linear programming techniques in order to estimate the farm household income under the current production systems and evaluate the economic impact of improved forage varieties for hay production. Furthermore, the economic viability of other changes in fodder and herd management was tested. Both groups were characterised by a dual-purpose system generating a gross income from the sale of both, milk and live animals in the amount of -21 (LC) and +1057 US$/farm and year (HC). Due to higher production costs for forages and better access to markets, LC communities were characterised by an integrated crop–livestock system whereas in the HC group income was mainly based on livestock. Introduction of improved and fertilized barley for hay production, was estimated to increase the annual farm income to 127 and 1257 US$ for LC and HC, respectively. This increase was accompanied by an increment of the animal number. Maintaining the animal number but increasing the milk production/cow by feeding additional forage was a less profitable option generating 50 and 1221 US$ of income per farm and year for LC and HC, respectively. The production of hay was limited by high costs (external labour) in LC communities and the restricted availability of family labour in the HC group. A scenario based on the use of improved cow genotypes led to the highest estimated annual farm income for HC communities (1280 US$) but was less favourable for LC. The modelling results showed that the best development strategy depends on various factors such as production costs, access to the markets and to irrigation and availability of different feed resources. 相似文献
13.
为准确实时跟踪羊只目标,进行疾病异常预警,实现奶山羊精细化养殖,本文基于DiMP跟踪模型,利用奶山羊跟踪对象单一且图像样本丰富的特点,结合迁移学习和类特定融合方法,设计了一种类特定的奶山羊目标跟踪模型,能够有效克服DiMP算法在跟踪类特定目标时定位精度不足的缺点。利用构建的奶山羊视频跟踪数据训练集对跟踪算法进行迁移训练,加快模型收敛速度,使评估网络预测出的边界框更贴合奶山羊真实框的位置和尺寸。在线跟踪阶段,针对目标模板仅采用第1帧特征制作整个序列的调制向量,导致该调制向量相对整个跟踪阶段特征不具代表性,与后续帧差异大的缺点,使用训练集制作包含奶山羊各种姿态的类调制向量,以指数消融方式更新奶山羊类调制向量与第1帧调制向量间的比重,增强边界框回归任务中的奶山羊特征与背景的判别性。提出的算法在测试集上的AUC(Area under curve)和精准度(Precision)分别为76.20%和60.19%,比DiMP方法分别提升6.17、14.18个百分点,跟踪速度为30 f/s,满足实时跟踪的要求。实验结果表明,提出的类特定奶山羊目标跟踪方法可用于监测复杂场景下奶山羊的运动,为奶山羊精细化... 相似文献
14.
This study reconstructed 21 years of household cattle population data in key resource (tula wells) and non-key resource (pond-water) rangelands in southern Ethiopia, as well as 15 years of government cattle breed conservation ranch data, to analyze the relationship between long-term rainfall and cattle population dynamics. For the key-and-non-key resource rangelands, we assessed the reproductive life of cows and the number of calves. For both the communal and ranch systems, we analyzed impacts of multiple droughts on calving rates and herd die-offs. Relationships between pre-drought and post-drought cattle populations were used to evaluate evidence of density-dependence. Breeding females in the key resource tula well rangelands had a longer reproductive life than in the pond-water rangelands, and they produced more calves per reproductive life. Average calving rates were 55% for the communal and 52% for the ranch. Greater reductions in calving rates during droughts implied reduced herd growth potential. Breeding females and immature animals were influenced to a much greater degree by inter-annual rainfall variability than were mature males. The data showed a downward spiral for the total cattle holdings over a 21-year period, with a decline of 54%. The evidence of density-dependence was relatively important at the local land use level as compared with the regional level. Cattle population below carrying capacity under ranch management did not reduce herd die-offs, suggesting that rainfall variability, not density, had greater influence on cattle population dynamics. Long-term trends of cattle populations in the communal and ranch systems synchronized with mean deviations of rainfall. Our results indicate that rainfall variability under the different management systems strongly influenced the dynamics of cattle population, calving rates and mortality. The claim that ranching could be a superior model for range management in Borana over the communal system was not confirmed. The decline in cattle population in southern Ethiopia indicates a need for improved drought management policy. The evidence that droughts were more harmful to breeding females and immature animals than to mature males suggested that drought management needs to focus on herd recruitment potential. For the herders in southern Ethiopia, drought management involved herd mobility and accumulation of herds during periods of favourable rainfall. In the future, the importance of government ranch could be in breed conservation for the maintenance of the Borana cattle breed through distribution of bulls during the drought recovery phase. 相似文献
15.
A computer model was developed to simulate forage systems on dairy farms. The model simulated alfalfa growth, corn silage and corn grain yields, harvest, storage, feeding and ration formulation for a dairy herd. A 26-year series of historical weather data from East Lansing, Michigan, was used to compare management and technological alternatives on the basis of average net return and year-to-year variations. For example, a four-cut alfalfa system was found to be more profitable than a three-cut system 90% of the time. The comparison of a hay system with a silage system was very sensitive to forage intake assumptions; the break-even point shifted from 120 ha to 40 ha when silage intake was increased by 5%. The model can be used to assess the impact of new forage conservation methods under a wide range of climatic and management conditions. 相似文献
16.
A. C. Bywater 《Agricultural Systems》1976,1(4):261-279
This paper is the second in a series describing a computer-based simulation model designed for use as a management control aid for the dairy herd and concerned with the intake and partition of nutrients by the cow. Milk production is represented in the model in two parts; the first estimates the potential milk yield for each 24 h simulation interval and the second is concerned with matching the available metabolites to the requirements associated with the potential yield. In each case, a conceptual scheme for inclusion in the model is outlined in relation to the relevant literature and the manner in which these schemes are represented in the model is described. 相似文献
17.
《Agricultural Systems》1998,56(3):305-322
A dynamic stochastic simulation model to study the relationship between reproductive performance and net-revenue in dairy herds is described. Herds included cows, heifers and calves described by individual characteristics and state variables. The latter were updated using time steps of one week in conjunction with calculations of milk revenue, sales revenue, feed costs, breeding costs, additional costs and net-revenue. Discrete events at the animal level, e.g. involuntary culling, estrous detection and conception were triggered stochastically. Voluntary culling was modeled using the future profitability of cows and potential replacements as determined by dynamic programming. Management and production system were defined by decision variables, e.g. estrous detection rate (EDRT), impregnation factor (IF) and rebreeding policy (RBP). Increases in net-revenue (NR) due to a 1% improvement in EDRT ranged from Cdn. $−2·9 at an EDRT of 75% to Cdn. $22·5 at an EDRT of 35% and were influenced by RBP. Hence, highest increase in NR due to improvement of EDRT can be expected at low reproductive efficiency. 相似文献
18.
《Agricultural Systems》1998,57(3):381-398
Ways of ‘tracking’ environmental fluctuations could be of value in limiting drought-induced mortality and increasing output. We examined a range of tracking policies, designed to tackle climatic variation, using a simulation model of a semi-arid grazing system. These compared annual sales designed to limit stocking rate, pre-emptive sales triggered by insufficient rainfall, and variable sales and stocking rate regimes determined by the current season's rainfall. Although the flexible stocking strategies did reduce mortality losses, compared with fixed stocking, they did not increase average annual sales. The main reasons for this are that major losses of stock are associated less with 1-year than with 2-year droughts, which are difficult to track, and that destocking can be really effective only if the productive potential of the herd can be re-established more rapidly than is possible from depleted herd resources. Tracking policies did have a considerable advantage in terms of reduced inter-annual variability of sales, which would be of economic benefit to the commercial livestock sector. For subsistence pastoralists, the traditional policies of maintaining the maximum number of breeding stock, and of hoping that most of them will survive drought, may be as close as ‘opportunistic’ management can get to dealing with drought. 相似文献
19.
A forage model and a cattle production model were interfaced and adapted for tropical production conditions in East Africa. The objectives of the modelling were to structure and conceptualise a complex system for better comprehension, thereby determining constraints on a traditional African grazing system. The model was designed to simulate the physical linkages between the scarce resource of forage and the outputs of cattle, meat and milk. The effects of improved management practices were examined for a traditional village livestock grazing system. Verification and validation for the baseline village herd were carried out using several different sources of data. A combination of a restricted breeding season, supplemental feeding during the dry season and a seasonal sales policy resulted in a 40% increase in net revenue to village producers above the baseline for a ten-year period. 相似文献
20.
《Agricultural Systems》1987,24(2):81-93
This analysis questions the assumptions that in a traditional farming system food production is primarily for home consumption and is not competitive with export crop (cocoa) production. Government planners and policy makers must look at the total operation of a farmer to understand the role of food crop production. In the case of Ghana in 1981 they needed to seek ways to make cocoa production relatively more profitable if the goal of increased cocoa production from small farms were to succeed.The analysis indicates why farmers were devoting scarce resources, particularly labor, to producing food crops in Ghana in 1981. Food crops were the most profitable both (1) in 1981 and (2) when the flow of income from the life of the trees was considered. Clearly, the farmers were demonstrating that they were rational economic men.In order to get an idea of what price cocoa must bring for it to be as profitable as the food crop systems, the price of cocoa was varied with all other prices held constant. The price of cocoa would have had to be approximately ¢400 per load of 30 kilograms in 1981. The government purchase price was ¢120 per load. Nor surprisingly, cocoa production in Ghana was declining steadily. 相似文献