• Decisions on forage product options based on genetic nutritional traits are important; however, environmental and management factors have the greatest influence on forage quality.

• Corn silage quality at time of harvest is primarily influenced by harvest maturity, kernel processing (PROC), theoretical length of chop, and length of storage time in silos.

• Corn offers a diversity of feeding options, which include corn silage, high-moisture shelled corn, high-moisture ear corn (HMEC), snaplage (SNAP), dry corn (DC), and stalklage.

• Legume, grass, and cereal forage quality is contingent on stage of maturity at time of harvest and wilting time to achieve proper dry matter (DM) content at time of ensiling the crop.

• Temperature and moisture are 2 environmental variables during plant growth that highly influence forage quality of corn, legumes, grass, and cereal forage crops.

Forage categories

Plants are classified as C3 and C4 carbohydrate producers, and the primary difference is within plant cells in which photosynthesis for carbon fixation events occur. C3 plants are cooler season crops that have a longer growing season and higher water demands (Table 1). In contrast, C4 plants are warm season crops that are water efficient and drought tolerant. Table 2 compares water usage requirements for several C3 with C4 crops; alfalfa is a C3 crop that has the highest water demand, whereas C4 sorghum crops use about one-third of the water required by alfalfa.1

Crop scientists monitor growth rates with calculators based on ambient temperature where using corn for example, growth starts at 7.2°C, maximizes at 22–30° C range, and ceases at 46°C. A Growing Degree Unit (GDU) calculation is used in the United States that is based on a linear relationship of growth to temperatures in the 10–30°C range. The GDU formula along with an example for corn is shown in Table 3. Using alfalfa in contrast, this crop starts growing at 5°C compared to corn at 10°C. Using the calculation for alfalfa and same daytime and night time temperature inputs as showing in the table, there would be 15.0 GDU accumulated for that day.2

Corn utilization as ensiled forage or grain

Corn is the predominant cereal crop grown throughout the world, because compared with all cereal crops, corn is unique in its ability to outyield the other crops on a ton/acre and nutrients/acre basis.2 Corn growth and development are typically categorized by a staging system that divides plant development into vegetative (before flowering) and reproductive grain development (after flowering) stages. The reproductive stages are key growth periods for capturing crop harvest opportunities intended for (1) whole-plant corn silage (WPCS), (2) high moisture ear corn (HMEC) or snaplage (SNAP), high-moisture shelled corn (HMSC), and (4) dry corn (DC). The reproductive maturity of corn is assessed by plant moisture, as shown in Table 4. WPCS is based on whole-plant moisture content, whereas high-moisture and dry grains are based on kernel moisture content.