Energy Use In Forage Production

Forage is an essential part of livestock production systems, especially for ruminant animals. However, this type of crop is not intensively managed since the monetary return it brings is very low. In this section, the typical energy output:input for the main forage productions, i.e. alfalfa, hay and corn silage production, will be examined.

Alfalfa

Alfalfa presents many advantages: it is one of the most productive forages, it is one of the most nutritious for livestock, and it is, like legumes, capable of fixing nitrogen from the soil. Consequently, alfalfa needs little nitrogen fertilizer, which is a high energy cost input. However, fuel and machinery still represent major energy inputs that lower the energy efficiency of alfalfa; if consumed fresh by livestock, alfalfa will cause bloat in ruminants, a sometimes deadly build-up of gas in the stomach, and therefore alfalfa must be harvested and dried before consumption. Overall, the energy input for alfalfa production is about 10.5 million kJ/ha and the yield is about 64.5 million kJ/ha, giving a relatively good output of 6:1.

Hay

Hay consists of numerous grass species that are grown in permanent hay fields and pastures. Animals can graze the hay as it grow, doing the harvesting themselves, or can also be harvested mechanically to feed the animals in feedlots or during the winter. When this is the case, fuel and machinery still represent the main energy expenditures. The average yield is in the range of 36 million kJ/ha and the total energy inputs are about 7.1 million kJ/ha, the energy output/input ratio being 5:1 for hay production.

Corn silage

Corn silage is made of mature corn plants that are cut, chopped and stored in a silo using anaerobic fermentation to be used as animal feed. On average, the energy inputs required for silage production are about 26.4 million kJ/ha and the yields are about 106 million kJ/ha. Thus, the energy output:input ratio for corn silage is 4:1.