Feed resources,livestock production and soil carbon dynamics in Teghane,Northern Highlands of Ethiopia

In the Northern Highlands of Ethiopia, integrated crop-livestock production within smallholder farms is the dominant form of agricultural production. Feed availability and quality are serious constraints to livestock production in Ethiopia in general, and in its Northern Highlands in particular. The objective of this study was to describe the relationship between feed availability and quality and live weight gain, milk and manure production and the soil C balance in Teghane, Northern Highlands of Ethiopia. The so-called JAVA model procedure, that essentially predicts metabolizable energy intake and animal production on the basis of feed quality and quantity, has been used and linked to a soil carbon balance. Forages were ranked according to their quality (on the basis of metabolizable energy intake by livestock) in descending order. Rations were formulated by stepwise including components of increasingly lower quality to calculate the trade-offs between feed quantity and quality. In the model, the soil C balance was described in relation to soil organic matter decomposition, C input from roots, grazing and/or harvesting losses, feed residues and manure. Moreover, an analysis of monetary values of live weight gain/loss, manure and draught power is included. The results of the model showed that mean daily live weight gain and milk production per TLU continuously increased with decreasing herd size, while total annual live weight gain reached a maximum (62 Mg) at the use of the 30% best feeds and a herd size of 630 TLU. Soil C balance at this level of feed use is negative and deteriorates with increasing feed use. The model estimated an optimum herd size of 926 TLU to attain the maximum combined monetary value of live weight gain, manure and draught power at 50% feed use. Actual herd size in the study area was 1506 TLU. Our results indicate that in areas where feeds of very different quality are available, maximum benefits from meat and/or milk production and soil C balance can be attained by selective utilization of the best quality feeds, through a storage and carry-over system.     

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.     

Development and evaluation of a pastoral simulation model that predicts dairy cattle performance based on animal genotype and environmental sensitivity information

A dairy cattle simulation model for pastoral systems that considers how dairy cow genotypes respond to different environments is described. The dairy cow is represented by five modules for maintenance, pregnancy, growth, body energy reserves and lactation with the influence of environmental factors on processes included within each module. Feed intake is predicted based on the requirements for maintenance, growth and pregnancy, and the dairy cow’s potential for yields of milk, fat and protein and body fat change in a given environment. The effects of various temporary environmental factors such as cow body condition score, climate, feed quality and the stage of pregnancy are all considered when predicting yields of milk, fat and protein, energy and dry matter intake. The model was evaluated using information from a prior experimental study with 1990s Holstein-Friesian dairy cattle of North American/European or New Zealand origin managed in a pasture-based system in early to peak lactation. The model was able to predict, to a high degree of accuracy, mean values for yields of milk, fat and protein, and concentrations of fat and protein. However for individual cows, feed intake and live weight change were less reliably predicted. The major source of error was a lack of simulated variation, rather than any systematic bias. The major advance of the model is its ability to predict performance from genetic and environmental sensitivity information for particular breeds, and its ability to predict feed intake and yields of milk, fat and protein concurrently.     

A general cattle production systems model. I: Structure of the model

A deterministic model for simulating beef cattle production under a wide range of management schemes and environments with cattle differing widely in genotypes for size, growth and milk production is described. In the model, genotypes are specified as production potentials, which are reached only if past and present planes of nutrition are adequate. Intake of forage and/or other feed is simulated as a function of the size and physiological status of the animals and the availability, digestibility and crude protein content of the feed. Animal performance is calculated from the nutrient intake and the animals' condition (fatness), degree of maturity and genetic potential. The model has been used for simulating beef cattle production under several widely differing sets of environmental and management conditions in Guyana, Colombia, Venezuela, Botswana, Texas and Mid-western United States and for simulating dairy-beef production systems in Colombia, Tanzania and Botswana. Results of simulations of existing conditions have coincided rather closely with actual production levels.     

A generalised model of feed intake and digestion in lactating cows

A generalised dynamic model for estimating voluntary consumption and digestion of feed by lactating dairy cows is described. Feed intake is assumed to be regulated either by metabolic factors relating energy intake to energy expenditure, or by physical factors associated with the capacity of the rumen to hold feed cell wall components. A representation of rumen function defined on an hourly basis provides estimates of digestion and passage of cell wall, and of the quantity of residue remaining in the rumen prior to the next meal from which physical intake limitations are calculated. Changes in regulation of energy intake and in maximum rumen capacity in response to changes in energy expenditure are subject to adjustment delays and are recalculated daily.Both qualitatively and quantitatively the model behaves well with respect to interactions between rumen function and short-term regulatory mechanisms over a wide range of feedstuffs. However, the dynamics of model behaviour over the long term-one lactation-indicate a systematic error in estimating changes in feed intake which is particularly evident in early lactation. The main cause of this error is thought to involve inadequacies in the representation of adjustment delays in the regulatory system.     

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.     

Feed conversion efficiency and the efficiency of the UK food chain

The efficiency of transfer of food energy across various components of the human food chain is calculated for the UK. The processing and presentation stages have overall efficiencies of transfer of 0·75 and 0·93, respectively, with foods of animal origin mainly showing higher efficiencies of transfer through these processes. The efficiency of agriculture, related to a hypothetical maximum potential biomass production, is 0·026, with relatively lower efficiencies for the livestock industries. Yields of food energy from crops and livestock in the UK are calculated as 33 and 4 GJ per hectare, respectively. The factors affecting animal feed conversion efficiency are examined and it is shown that there is a potential conflict between high animal feed conversion and overall food chain efficiency. The consequences of this conflict—and possibilities for optimisation—are examined in terms of a simple resource allocation model.     

The potential contribution of forage shrubs to economic returns and environmental management in Australian dryland agricultural systems

In face of climate change and other environmental challenges, one strategy for incremental improvement within existing farming systems is the inclusion of perennial forage shrubs. In Australian agricultural systems, this has the potential to deliver multiple benefits: increased whole-farm profitability and improved natural resource management. The profitability of shrubs was investigated using Model of an Integrated Dryland Agricultural System (MIDAS), a bio-economic model of a mixed crop/livestock farming system. The modelling indicated that including forage shrubs had the potential to increase farm profitability by an average of 24% for an optimal 10% of farm area used for shrubs under standard assumptions. The impact of shrubs on whole-farm profit accrues primarily through the provision of a predictable supply of ‘out-of-season’ feed, thereby reducing supplementary feed costs, and through deferment of use of other feed sources on the farm, allowing a higher stocking rate and improved animal production. The benefits for natural resource management and the environment include improved water use through summer-active, deep-rooted plants, and carbon storage. Forage shrubs also allow for the productive use of marginal soils. Finally, we discuss other, less obvious, benefits of shrubs such as potential benefits on livestock health. The principles revealed by the MIDAS modelling have wide application beyond the region, although these need to be adapted on farm and widely disseminated before potential contribution to Australian agriculture can be realized.     

A general cattle production systems model. Part 2—Procedures used for simulating animal performance

The methods used for simulating animal performance in the Texas A&M Cattle Production Systems Model are given and discussed. The GRO subroutine is used to calculate feed intake, changes in weight and skeletal size and, if appropriate, milk production level. Growth rates from the GRO subroutine, size, condition, time since calving and the fraction of the animals in the class that were in oestrus the previous month are used in the FERT subroutine to simulate the occurrence of oestrus and conception in open, breeding females. Death rates are simulated in the DIE subroutine as functions of the time of the year, the age and condition of animals in the class and, for cows, whether or not they calved during the current or previous month. The information from these subroutines is used to update the numbers and characteristics of animals in the various classes at the end of each month of simulation.     

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.     

A simulation model to predict body weight gain in growing steers grazing tropical pastures

A simulation model was developed to predict performance of growing steers grazing tropical pastures. The model is deterministic and integrates the effects of protein and energy intake from forages and supplements. Protein deposition was predicted by the PDI system. Energy balance was based on the California Net Energy System with modifications for animal activity and heat stress. Three output results of average daily gain (ADG) were obtained with the model: from energy (ADGe), from PDIN (ADGpdin) and from PDIE (ADGpdie). The model was validated using data from five experiments (29 treatments) conducted in the humid tropics of Mexico. The model did not accurately predict weight loss in steers based on energy or protein intake. Estimation of ADG from energy intake was successful in only six treatments, under-estimating gain by 30% with ADGe. Gain was predicted by ADGpdin in only one treatment, showing a general under-estimation of 40%. Values of ADGpdie were similar to the observed values in 10 treatments, under-estimating gain in 70% of the observed values. Prediction of performance in grazing steers in tropical conditions requires more information about environmental factors, as well as precise and accurate determinations of intake.     

A short-term mechanistic model of forage and livestock in the semi-arid Succulent Karoo: 1. Description of the model and sensitivity analyses

This series of two papers describes a mechanistic model that simulates within years the productivity of vegetation and livestock on the communal semi-arid rangeland of the Succulent Karoo of South Africa. The model enables users to evaluate short-term management decisions on the production of milk and meat and to develop sets of equations and rules for long-term models designed to examine the effects of different strategies on the sustainability of the ecosystem.A soil moisture module partitions daily rainfall between runoff, infiltration and drainage and also simulates the loss of soil moisture by evaporation and transpiration. Forage production by different types of plant is modelled in relation to soil moisture and the present potential for growth. Three factors are assumed to influence the animal’s preference for a specific type of plant or part of a plant: relative abundance, ease of harvesting and digestibility. The model combines three mechanisms of food intake regulation: the rate at which the animal is able to eat forage, physical capacity of the digestive system, and, in young animals, their growth potential. Metabolisable energy intake is partitioned between maintenance, accretion/depletion of body protein and fat, conceptus growth and milk production. Reproductive and survival rates are simulated in relation to predicted liveweight and liveweight changes for the different age classes of livestock.     

基于RFID的种奶牛母本选育体系的实现

传统的奶牛品种选育工作,主要依靠畜牧专家的经验和奶牛饲养过程中的历史记录数据进行人工综合评定,该方法存在效率低、准确度低以及人为影响因素大等缺点。为此,利用RFID技术进行奶牛个体标识,并把畜牧专家的专业知识与经验转换为数据库中的数据表达模式与程序算法,依靠SQL Server 2005和VS.net 2008平台开发奶牛品种选育系统。系统不仅能管理奶牛的日常生产活动,而且能根据历史累积数据和设计好的评估算法进行种奶牛母本的选择。系统研制完成后,在某小型奶牛养殖场成功应用并取得畜牧专家的认同。     

Economic and environmental evaluation of three goal-vision based scenarios for organic dairy farming in Denmark

The objective of this study was to explore the sustainability of future organic dairy farming systems in Denmark, by evaluating the economic and environmental consequences of three scenarios at the farm level based on different visions of future sustainability leading to different farm-based goals. The future sustainable organic dairy farming systems were deduced from participative sessions with stakeholders, and used to define specific scenarios and related key parameters. Parameterization of the scenarios was based on model simulations and the invoking of expert knowledge. Each scenario was designed to fulfil different aspects of sustainability. The business as usual scenario (BAU) was driven by economic incentives and implemented new technologies and measures to enhance productivity and efficiency. This scenario was expected to be the mainstream strategy of future organic dairy production in Denmark. In the animal welfare scenario (ANW), economic efficiency was subordinate to animal welfare, and measures to improve animal welfare, such as lower milk yield, extra grazing area and a deep-litter barn, were incorporated. The environmental scenario (ENV) was designed to minimize N losses into the environment, reduce emission of greenhouse gases and the use of fossil energy, and was based on self-sufficiency regarding nutrients and feed. The economic evaluation of the scenarios was based on quantification of farm profitability (i.e. net profit), whereas environmental evaluation was based on the quantification of the N-surplus per ha, emission of greenhouse gases, and use of fossil energy per kg energy-corrected milk (ECM).Compared to prolonging the current main stream strategy (BAU), the evaluation of scenarios revealed that investing in animal welfare comprised trade-offs regarding farm profitability, climate change and the use of fossil energy. In ANW, net profit per farm was almost 39 k€ lower than in BAU, whereas emission of greenhouse gases and energy per kg ECM was 8% and 3% higher, respectively. Minimizing environmental impact in ENV reduced local as well as global environmental impact without an economic trade-off. Greenhouse gas emission per kg ECM was 5% lower and fossil energy use was 11% lower than in BAU. The N-surplus of ENV was 80 kg per ha, whereas the N-surplus was approximately 116 in both BAU and ANW. Prolonging the current main stream strategy (BAU) resulted in a high local environmental impact, a moderate global environmental impact and a high economic risk related to changes in milk price or costs.     

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.     

Dairy farm nutrient management model: 2. Evaluation of different strategies to mitigate phosphorus surplus

To reduce (P) surpluses on dairy farms and thereby the risk of P losses to natural waters we studied different management alternatives by a nutrient balance model described in the companion paper. The strategies evaluated mitigating the P surpluses were: mineral P fertilisation, dietary mineral P supplementation, replacement rate, animal density, production level, feeding intensity, dietary P concentration and nutrient efficiency in crop production. Responses to several interventions (e.g. mineral P fertilisation, purchased feed P, replacement rate) were similar to those observed in Finnish field studies. Reducing or completely giving up the use of purchased mineral P fertilisers was the most efficient measure to reduce P surplus. The slope between the amount of mineral fertilisers and P surplus was 0.98-0.99 (in the field data 1.0). Increased animal density resulted in a greater P surplus, but the slope between P input from purchased feed and surplus was considerably smaller (0.65) than that of P fertilisation. Increasing milk yield with improved genetic potential of the cows would have minimal effects on P surplus per unit of product, but it would increase P surplus per hectare. When the intensity of energy and protein feeding was increased, P surplus rose markedly both per unit of product and hectare. This is (1) due to increased dietary P concentration and (2) due to smaller marginal production responses than those calculated from feeding standards. Reducing dietary P concentration by constraining P excess per kg milk in least-cost ration formulation improved P efficiency in milk production and dairy farming system. However, feed cost increased as low P energy (sugar-beet pulp) and protein (soybean meal) supplements are more expensive than cereal grains or rapeseed feeds. Improving the nutrient use efficiency in crop production had a strong influence in the whole-farm efficiency and P surplus. The modelling results showed that Finnish dairy farms have a great potential to improve P efficiency and reduce P losses to the environment, even by increasing production intensity (milk/ha). It is concluded that the most cost-effective scenario to mitigate P surpluses at a dairy farm would be to reduce or give up the use of mineral P as fertilisers and supplements, and to improve the use of present soil P reserves.     

Life cycle assessment of high- and low-profitability commodity and deep-bedded niche swine production systems in the Upper Midwestern United States

We used ISO-compliant life cycle assessment to evaluate the comparative environmental performance of high- and low-profitability commodity and deep-bedded niche swine production systems in the Upper Midwestern United States. Specifically, we evaluated the contributions of feed production, in-barn energy use, manure management, and piglet production to farm-gate life cycle energy use, ecological footprint, and greenhouse gas (GHG) and eutrophying emissions per animal produced and per live-weight kg. We found that commodity systems generally outperform deep-bedded niche systems for these criteria, but that significant overlap occurs in the range of impacts characteristic of high- and low-profitability production between systems. Given the non-optimized status of current deep-bedded niche relative to commodity production, we suggest that optimizing niche systems through improvements in feed and sow herd efficiency holds significant environmental performance improvement potential. Drivers of impacts differed between commodity and deep-bedded niche systems. Feed production was the key consideration in both, but proportionally more important in niche production due to lower feed use efficiencies. Liquid manure management in commodity production strongly influenced GHG emissions, whereas solid manure management increased eutrophication potential due to outdoor storage in deep-bedded niche production. We further observe an interesting but highly imperfect relationship between economic and environmental performance measures, where profitability tracks well with resource (in particular, feed) throughput, but only indirectly with emissions intensity.     

Simulation of beef cattle production systems in the Llanos of Colombia—part I. Methodology: An alternative technology for the tropics

A simulation model was developed to study voluntary forage intake, energy requirements for maintenance, liveweight change and calving rate of grade Zebu cows in the Llanos of Colombia. Multiplicative correction factors were fitted to intake and maintenance requirement prediction equations researched from the literature to account for reduced intake due to sparse regrowth of recently burned native savanna and to conditions of mineral deficiency, increased intake and decreased maintenance requirement during periods of high compensatory gain during the rainy season, and increased intake and maintenance requirement due to the effects of lactation and gestation. A frequency distribution was constructed relating liveweight at time of mating to subsequent calving rate, and this was used to simulate the calving rates of cow herds in the Llanos. Use of the model would allow prediction of the amount of improved pasture or supplemental feed that would be necessary to raise calving rates in a particular herd to an acceptable level, defined as at least three calves per cow every four years. The model was fitted by computer and was then run on programmable calculators. This type of simulation is suited to regions of the world in which computer time is expensive or unavailable. Verifications, validations and experimentation with the model are presented in a companion paper.     

Modelling the economics of animal health control programs using dynamic programming

A new application of an optimization tool, dynamic programming (DP), is described to model the economics of animal health control programs. To demonstrate the value of this technique, a model is applied to determine optimal net benefits of controlling East Coast fever (ECF) in Malawi Zebu cattle in the Lilongwe plateau. The objective function was the present value of net benefits due to treatment, defined as mortality savings minus treatment costs. Mortality savings were based on decreased mortality from ECF following treatment. Model constraints included herd size, animal (herd) nutritional requirements, and program budget. Treatment options were tank dipping in acaricide, and vaccination. Secondary data from a dipping trial of 1800 Malawi Zebu cattle conducted from 1991 to 1994 were used to determine probabilities of mortality. Total optimal net benefits of long-term treatment (25 years, i = 10%) from vaccination (Malawi Kwacha (MK) 21 069) exceeded benefits for treatment with chlorfenvinphos acaricide (MK15 203).     

An optimization model for zero-excess phosphorus management

Livestock production in the 21st century is moving in the direction of higher animal densities. Accompanying livestock expansion is the challenge of manure handling and utilization. A model for zero-excess phosphorus (ZEP) management has been developed for a dairy-crop operation that is based on multicriteria optimization. ZEP management practices are identified by simultaneously minimizing excess manure phosphorus, feed cost, and cropland requirement. System components include commercial fertilizer application, feed crop production, P storage in the soil profile, surface runoff, procurement of feed supplements, ration formulation, dairy herd structure and dynamics, manure handling, manure storage, and manure spreading. Manure is recycled as a fertilizer nutrient source in crop production. ZEP management practices include a cropping system, nutrient applications, and animal rations which are characterized by low feed cost and maximum use of land resources.