原题
| Feeding system | Amount of milk per goat per year (kg) | Milk revenue (€ per goat per year) | Feeding cost (€ per goat per year) | Gross margin (€ per goat per year) |
| Grazing | 705 | 480.8 | 152.9 | 364 |
| Grass silage | 830 | 566.1 | 179.3 | 427 |
| Cornsilage | 931 | 653.6 | 220.6 | 456 |
| Alfalfa hay | 925 | 649.4 | 245.1 | 423 |
Gross margin refers to the profit after subtracting certain costs (e.g., feeding cost) from total revenue, which may include more than milk revenue. While Greece, Turkey, and Spain are established leaders in the global goat dairy industry, countries like Portugal and Chile have smaller but growing goat dairy sectors. Seeking the feeding system that will give her the greatest profit, a Portuguese farmer consults research published in 2019 by the Instituto Nacional de Investigación y Tecnología Agraria y Alimentaria comparing the economic indicators of different feeding systems on Spanish goat farms.
Which consideration, if true, should make the farmer most hesitant to rely on what the table suggests is the most profitable feeding system?
ACorn silage is typically mixed with soybean meal; hence, the feeding cost associated with corn silage is likely to fluctuate with the global price of soybeans, a commodity that has historically been subject to significant year-over-year price volatility.
BIf properly processed and stored under airtight conditions, corn silage can retain its quality for over a year; hence, feeding systems that use corn silage are assured of a consistent feed supply that is less vulnerable to weather conditions than are more traditional feeding systems, such as grazing.
CThe labor costs of grazing livestock in Portugal (e.g., herding, fencing, and moving) are likely comparable with those in Spain; however, farmland in Portugal that is suitable for grazing is scarcer and may be more expensive than in rural southern and central Spain, where many Spanish goat farms are located.
DGoats expend energy grazing and therefore tend to produce less milk than goats fed silage or fresh-cut grass; moreover, grazing goats’ diets are heterogeneous and seasonally variable, so milk production could decline when the nutritional value of available vegetation is poor.
正确答案：A
解题思路
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