A report by AG's Animal production service (AGAP) says that, in terms of digestible nutrients, mulberry produces more than most traditional forages. The leaves can be used as the main feed for goats, sheep and rabbits, as supplements replacing concentrates for dairy cattle, and as an ingredient in the diets of monogastric livestock, such as pigs. "It is surprising," says animal nutrition specialist Manuel Sánchez, who recently helped conduct an AGAP email conference on mulberry, "that a plant used to feed the silk worm, which has high nutritional feed requirements, has received such limited attention from livestock producers, technicians and researchers."
Trees travelled with silk worms. Over the centuries, mulberry trees have accompanied the spread of silk worm production throughout the world - to the temperate areas of Europe and North America and the tropics of Asia, Africa and Latin America. Mulberry varieties have adapted to a range of environments, from sea level to altitudes of 4,000m, and from the humid tropics to the semi-arid lands of the Near East. But in only in a few places have they been used as feed for livestock.
The breakthrough came in the 1980s, in Costa Rica, where a farmer who had raised mulberry trees for a failed silk worm project fed the leaves to his goats. Impressed by mulberry's apparent palatability and by the performance of his animals, he shared his experience with scientists at the Tropical Agriculture Research and Training Center (CATIE, Costa Rica), who decided to include mulberry in their tree fodder evaluations. Around the same time, the International Centre for Research in Agroforestry in Kenya and the Livestock Production Research Institute in Tanzania also began, independently, to conduct agronomic and animal trials of the tree.
In trials with growing pigs, replacing 15% of a commercial concentrate with mulberry leaf increased daily weight gains from 680g per day to almost 750g per day. Offered mulberry leaves, Angora rabbits reduced their intake of pellets by up to 40%, representing a considerable saving in feed costs. Other researchers have found that including dried mulberry leaf meal in the mash of laying hens leads to better egg yolk colour and increased egg size and production. "The long selection and improvement of mulberry has made it comparable to - and often better than - many other forage plants in terms of nutritional value and yield of digestible nutrients per unit of area, specially in tropical environments," says FAO's Manuel Sánchez. "Yield, quality and its availability worldwide make mulberry a very important option to intensify livestock systems, especially in places where enough nutrients can be applied to obtain maximum response in biomass production. The greatest immediate impact would be in tropical areas if introduced as supplement to lactating cows and as feed to growing calves."
Strategic fodder. Meanwhile, FAO's Crop and grasslands service (AGPC), is promoting the cactus pear as a strategic fodder in arid and semi-arid areas. The idea of using Opuntia to feed livestock is not recent - during the 19th century, there was extensive trade in cactus in cattle-raising regions of Texas, USA, and both wild and cultivated cactus are used today in Tunisia, Mexico and South Africa as an emergency forage during drought. But a 1995 FAO study found that more research on cactus was needed and called for "serious R&D in a well-focused programme". Since then, AGPC has helped establish an international technical cooperation network on cactus pear, initiate a horticultural variety information bank, and sponsor a series of international congresses and workshops on the plant.
In North Africa and the Near East, Opuntia has become an important subsistence crop, and an estimated 700,000 to one million ha of it have been planted, mainly in low rainfall areas, to provide feed for livestock during droughts (to encourage plantations, the Tunisian government provides farmers with free growing material, and subsidizes their soil preparation and maintenance costs). As well as providing fodder, the cactus pear helps alleviate pressure on watering holes during the summer and drought periods - research shows that sheep's water consumption drops to nil when their cactus intake reaches about 300g, by dry weight, per day.
AGPC cautions that cactus pear does not provide a balanced diet - it should be fed in association with fibrous foodstuffs (such as straw and hay) and needs to be supplemented with nitrogen. However, as an emergency fodder and a reliable source of forage in low-rainfall areas, it has few equals.
Published September 2000