The objective of this study was to compare the economic performance of 2 sward types [perennial ryegrass (PRG; Lolium perenne L.) sown with or without white clover (Trifolium repens L.)] grazed by 3 cow genotypes. Physical performance data were collected from a 4-yr systems experiment based at Clonakilty Agricultural College, Clonakilty, Co. Cork, Ireland. The experiment compared 2 sward types (PRG-only swards and PRG-white clover swards), with each sward type being grazed by cows from 3 genotypes [Holstein-Friesian (HF), Jersey × HF (JEX), and Norwegian Red × JEX (3-way)]. All systems were stocked at 2.75 cows/ha with fixed fertilizer applications and concentrate supplementation. The data supplied 6 production systems (2 sward types × 3 cow genotypes). The production systems were modeled using the Moorepark Dairy Systems Model (stochastic budgetary simulation model) under 2 scenarios, one in which land area was fixed and one in which cow numbers were fixed. The analysis was completed across a range of milk prices, calf prices, and reseeding programs. The analysis showed that in the fixed-land scenario with a milk price of €0.29/L, adding white clover to PRG swards increased profitability by €305/ha. In the same fixed-land scenario, JEX cows were most profitable (€2,606/ha), followed by 3-way (€2,492/ha) and HF (€2,468/ha) cows. In the fixed-cow scenario, net profit per cow was €128 greater for PRG-white clover swards compared with PRG-only swards. In this scenario, JEX was the most profitable per cow (€877), followed by HF (€855) and 3-way (€831). The system that produced the highest net profit was JEX cows grazing PRG-white clover swards (€2,751/ha). Regardless of reseeding frequency or variations in calf value, JEX cows grazing PRG-white clover swards consistently produced the highest net profit per hectare.

中文翻译：

---

牧场类型和奶牛基因型不同的牧场生产系统的经济比较。

这项研究的目的是比较吃草了3种母牛基因型的2种草地类型的经济表现[多年生黑麦草（PRG;黑麦草），有无三叶草（Trifolium repens L.）]。物理性能数据是从位于爱尔兰科克Clonakilty的Clonakilty农业学院的4年系统实验中收集的。实验比较了2种草皮类型（仅PRG草皮和PRG白三叶草草皮），每种草皮均由3种基因型的奶牛放牧[Holstein-Friesian（HF），Jersey×HF（JEX）和Norwegian Red×JEX （三向）]。所有系统的养牛量为2.75头/公顷，固定施肥和补充浓缩物。数据提供了6种生产系统（2种草地类型×3种母牛基因型）。使用Moorepark乳制品系统模型（随机预算模拟模型）在2种情况下对生产系统进行建模，一种情况是固定土地面积，另一种是固定母牛数量。该分析在一系列牛奶价格，小牛价格和补种计划中完成。分析显示，在牛奶价格为0.29欧元/升的固定土地方案中，在PRG草地上添加白三叶草可使盈利提高305欧元/公顷。在相同的固定土地情景下，JEX奶牛的获利最高（2,606欧元/公顷），其次是三向奶牛（2,492欧元/公顷）和HF（2,468欧元/公顷）奶牛。在固定奶牛的情况下，与仅使用PRG的牧草相比，使用PRG的白三叶草饲养的每头母牛的净利润要高出€128。在这种情况下，JEX是每头奶牛最赚钱的地方（877欧元），其次是HF（855欧元）和三元奶（831欧元）。产生最高净利润的系统是放牧PRG白三叶草草皮的JEX母牛（2,751欧元/公顷）。不论播种频率或犊牛价格变化如何，放牧PRG白三叶草的JEX母牛每公顷始终产生最高的净利润。