Farmer's Smart Use of Feed Q&A

Author: Gong Shengyin
Publisher:
Publish Date: 2005-03-01
Features:
Segment: The main factors affecting the chemical composition and nutritional value of feed include external environment, the plant itself, and processing and modulation methods.
8. How does the external environment affect feed nutritional value?
Soil fertility: The richness or poverty of the soil not only affects the yield of plants grown on it but also influences the chemical composition of different parts of the plant. The same grass grown on fertile land not only has a high yield but also a high nitrogen content, whereas grass grown on poor land is the opposite. Therefore, fertilization is an important measure to increase feed production and nutritional value. For example, the mineral content in the soil can determine the mineral content in feed. In regions where the soil lacks copper, zinc, iodine, and selenium, the feed produced in these areas also lacks these minerals. Long-term feeding of such feed can lead to anemia, swayback, and white muscle disease in livestock and poultry in these areas. Northwest and Northeast China have such endemic diseases. If appropriate fertilizers are applied in these areas, these diseases can be avoided or reduced.
Climate conditions: Differences in climatic factors such as annual rainfall, temperature, humidity, and sunlight have a great impact on photosynthesis, metabolism, and growth and development of plants. Therefore, the nutrients contained in the plants also vary. China has vast land and complex natural conditions, so the nutritional value of the same plant varies greatly. When using feed nutritional value tables, this factor must be considered. For example, corn kernels from northern Shaanxi in Shaanxi Province contain 9% to 11% crude protein, while corn from the Guanzhong Plain has a crude protein content of 7% to 9%.
Cultivation techniques: Differences in sowing time and cultivation techniques of various feed crops also lead to differences in nutritional composition. For example, when grass crops are densely planted, their stems are finer, so they contain less fiber but higher crude protein content. Therefore, artificially cultivated pasture grasses have higher nutritional value than wild plants.
9. How does the plant itself affect feed nutritional value?
Plant varieties: Different varieties have significant differences in their nutritional composition. For example, the content of various nutrients in corn stalks and oat grains of different varieties varies greatly. It can be seen that when cultivating feed, the variety should be selected, choosing the variety that can obtain the most nutrients per unit area. Some countries in the world have bred high-protein, high-lysine corn varieties for livestock, and China also has such varieties.
Plant parts: Different parts have different nutritional compositions and digestibility. Generally, leaves contain more crude protein and vitamins than stems, whereas stems contain more crude fiber and lignin. For example, in alfalfa, lysine accounts for 4.4% of protein in stems but 4.9% in leaves; arginine accounts for 4.6% of protein in stems but 5.9% in leaves; histidine accounts for 2.2% of protein in stems but 3.0% in leaves. Carbohydrates not only vary in content but also in form in different parts of the plant, mainly in the form of starch, crude fiber, and lignin. Lignification in plants begins at the base of the stem and gradually moves upward, eventually affecting leaves, then glumes and seeds. Most carbohydrates in stems are crude fiber, while carbohydrates in seeds are mainly starch with little crude fiber. Therefore, the stem-to-leaf ratio (leaf/stem) is important for grass feed. The distribution of minerals is also affected by the plant parts. Calcium and magnesium are mainly present in leaves, phosphorus is mainly in seeds, and potassium is distributed in stems and tubers. Not only do the nutritional compositions differ in different parts of the plant, but the digestibility also varies. Generally, nutrients in leaves have a higher digestibility than those in stems.