This archive report was first published on 29 June 2020.
With the increasing demand for pig farming, finding affordable and nutritious feed options has become a significant challenge for farmers. One solution is to use sweet potato vines to create a silage that can be fed to pigs.
According to a livestock expert, pigs are legally raised in confinement as a control measure against African Swine Fever (ASF). However, their simple stomach nature makes it necessary to feed them on commercial feeds that consume 60-80 per cent of production costs.
Using sweet potato vines as a feed supplement can help reduce these costs. The vines can be used fresh, dried, or fermented into silage, which enhances the quality of the feed material by converting nitrogen to protein.
Energy and protein are the main nutrient components in a pig's diet. Grains such as maize, barley, wheat, sorghum, and oats have traditionally supplied energy, while protein has come from meals produced from oilseeds such as soybeans and canola.
However, processing some of the feed inactivates anti-nutritional factors. For example, raw whole soya beans contain an anti-nutritional factor that inhibits utilisation of the trypsin enzyme resulting in decreased palatability and use.
But heat processing inactivates the anti-nutritional factor. Other ingredients that contain anti-nutritional factors include canola, lupins, and potato chips.
Kenya has increased sweet potato production in the recent past, but its utilisation for animal feed, especially pigs, is still low. The crop is drought-resistant, and the tuber and leaves are palatable and highly digestible.
Planting sweet potato fodder involves digging hills of soil 15cm deep, cutting vines of about 30cm long, and burying three-quarters in the soil. The vines will need a handful of manure per hole and fertiliser at the rate of 60kg per hectare.
The plant matures in three to four months and yields five to six tonnes of fresh vines per acre. Cutting interval is two to three months depending on the weather.
Harvest and wilt the vines for three days in a partial shade, then chop them into 5-1cm long pieces. Chop tubers into 2.5cm2 pieces and place the contents in alternating layers into a silage bag, drum, or pit at the rate of 70 per cent vines, 30 per cent tubers, and 0.5 per cent salt or sun-dried poultry manure.
Make 10cm slits at the bottom of the silage tube to enhance effluent drainage. The silage will be ready for utilisation after 30 days.
The silage is best fed to pigs that are over three months of age and weigh more than 25kg. A pig consumes about 3-6 per cent of its body weight per day, and 40 per cent of this can come from the silage and 60 per cent from pig feeds (concentrates).
