Nutritional improvement of maize silage for dairying: mixed crop silages from sole and intercropped legumes and a long season variety of maize. 2. Ensilage

Abstract

The suitability of a number of locally adapted legumes was tested for inclusion in mixed maize-legume silage on the hypothesis that the maize would provide the fermentable carbohydrate for ensiling of both crops while the legume would improve the protein content of the silage. Legume and maize forage were layered equally for ensiling in plastic bags and compressed. Silage fermentation characteristics and nutritive value were determined after 10 days. An insight into the optimum legume-maize ratio was sought by adding soyabean biomass to the maize in varying proportions, increasing from 10 to 80%. None of the mixed crop silages had a dry matter content significantly outside the optimum range of 240–320 g kg −1 except for that containing 10% grain soyabean. The pH values of the silages range from 3.9 to 6.8 but the amount of ammonia nitrogen as a proportion of total nitrogen was 13.2% or less. Nutritional content of the legume-maize silages showed that protein content significantly improved to between 9.3 (yellow lupin) and 15.3% (forage soyabean) over that of pure maize silage and up to 16.3% with 80% grain soyabean. All silages were more than 50% digestible except velvet bean silage, however, maximum acceptable neutral detergent fibre levels of 65% were exceeded significantly by velvet bean, cowpea and silverleaf silages and silages with < 30% grain soyabean. All silages had metabolisable energy values of over 8 MJ kg −1 except velvet bean (7.3 MJ kg −1). It is concluded that it is possible to produce silage of reasonably good quality, using methods appropriate to small-scale silage technology, from most of the tested legumes when mixed with maize at 50% by volume, and results indicate that the proportion of legume should be at least 40%. Further research using other adapted cereals and ensilage techniques is indicated.