We are currently testing the nutrient levels in the blood of our animals as we feed them tree leaves, and while tree leaves may seem unusual, they are common foods for animals in most other places. The TDN, RFV, and mineral content varies considerably from forage to forage, even two different fields of grass will be significantly different in most respects depending on species of grass, or variety of alfalfa. The FAO and many foresters agree, trees are no different. However, studies (FAO: 4.1 The Nutritive Value of Tree Legumes, Dr.B.W. Norton http://www.fao.org/ag/AGP/AGPC/doc/Publicat/Gutt-shel/x5556e0j.htm) indicate that there is little difference between tree leaves and most standard hays.
Many people supplement based on a belief of what they are feeding their animals. Often, they are wrong in their assumptions, and attempts to perfectly balance diet are futile unless you are working with laboratory formulated feeds, such as those which are manufactured by Purina and other vendors.
Leaves are excellent food for not only ruminants (it is the food of choice throughout most of the world, though in the Americas, we are just discovering this), but also animals with simpler stomachs. Even people eat quantities of tree leaves without harm. Some tree leaves are poisonous in small quantities, others are poisonous in large quantities; others are wholesome and healthsome in even minute quantities. Many trees have medicinal properties.
The answer for those who supplement to overcome deficiencies in diet when using conventional grass and alfalfa feeds is the same for those who supplement to overcome deficiencies in tree leaf diets: hedge on the side of too much rather than too little. Few nutrients cause disease when overfed in moderate amounts. In Colorado, selenium deficiency is common because the soil is so poor in selenium. Most leaves have about 10% crude protein, with about 60% digestibility, and while oaks may have up to 15% mean taninnic acid equivalent, most trees typically have much less than half that and 15% is not bad, if the oaks are diluted with other feed ("Nutritive Value of Tree Leaves in the Kansas Flint Hills," JR Forwood and CE Owensby: Journal of Range Management 38(1), January 1985). I, myself, enjoy the linden leaves best. They make an excellent salad.
Posted by Mary @ 05:23 PM MST [ Comments  ]