Context The productivity of Ethiopian smallholder farms is considered to be low owing to different factors such as feed shortage, lack of breeding strategies, disease prevalence and missing marketing strategies. Aim The main objective of the study was to develop a dynamic, stochastic herd model by adopting system dynamic modelling methodology for evaluation of the effect of increased feed availability (forage production) in combination with different fattening strategies on herd dynamics and profitability of an Ethiopian sheep population. Methods Forage production utilising part of smallholder farmers’ cropland was built into a dynamic simulation model. Two alternative feed-supply systems were evaluated: turning 25% and 50% of the current cropland into area used for forage production. The simulation period was 20 years, the first 10 years representing the baseline fattening scenario (culled rams fattened). For the last 10 years, genetic selection was introduced and two scenarios were evaluated: fattening of culled rams (Scenario I) and fattening of young rams (Scenario II). Key results Increasing the feed supply resulted in an increase to the herd size when the model balanced dry matter supply and demand of the herd. Fattening of young rams (Scenario II) with genetic selection was significantly more profitable than the baseline and Scenario I in both of the simulated alternative feed-supply systems. This can be used for regular cash generation, which might reduce disposal of animals at lower price in cases of need for emergency cash. Conclusions Overall, the simulation model demonstrates that production of improved forage crops should be combined with selective breeding and an appropriate finishing strategy. The competition for resources (land and labour) with crop production, forage seed shortage and extended family size are other challenges raised by smallholder farmers for the feasibility of the two alternative feed-supply systems.

中文翻译：

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通过系统动力学模型评估埃塞俄比亚绵羊种群的饲料供应增加和不同的育肥策略

背景 由于饲料短缺、缺乏育种策略、疾病流行和营销策略缺失等不同因素，埃塞俄比亚小农农场的生产力被认为很低。目的 本研究的主要目的是通过采用系统动态建模方法来开发动态、随机的畜群模型，以评估增加饲料可用性（草料生产）结合不同育肥策略对埃塞俄比亚绵羊的畜群动态和盈利能力的影响人口。方法利用部分小农耕地进行牧草生产，建立动态模拟模型。评估了两种可供选择的饲料供应系统：将当前农田的 25% 和 50% 转化为用于饲草生产的面积。模拟周期为 20 年，代表基线育肥情景的前 10 年（剔除公羊育肥）。在过去的 10 年中，引入了遗传选择并评估了两种方案：淘汰公羊的育肥（方案 I）和幼羊的育肥（方案 II）。主要结果 当模型平衡牛群的干物质供应和需求时，增加饲料供应导致牛群规模的增加。在两种模拟的替代饲料供应系统中，通过遗传选择育肥小公羊（情景 II）的利润明显高于基线和情景 I。这可用于定期产生现金，这可能会减少在需要紧急现金的情况下以较低价格处置动物。结论 总体而言，模拟模型表明，改良饲料作物的生产应与选择性育种和适当的整理策略相结合。与作物生产、饲料种子短缺和扩大家庭规模有关的资源（土地和劳动力）竞争是小农对两种替代饲料供应系统的可行性提出的其他挑战。