Forage yield, nutritive value, and ensilability of sweet pearl millet and sweet sorghum in five Canadian ecozones

Abstract

Sweet pearl millet [Pennisetum glaucum (L.) R. Br.] and sweet sorghum [Sorghum bicolor (L.) Moench], previously tested for ethanol production, were evaluated as high sugar crops for animal feeds to possibly replace silage corn (Zea mays L.). We compared the forage yield, nutritive value, and ensilability of one hybrid of sweet pearl millet and two of sweet sorghum to a locally adapted silage corn hybrid in five Canadian ecozones. Forage yields of sweet pearl millet and sorghum were similar to that of silage corn in the Boreal Shield, Mixedwood Plain, and Atlantic Maritime ecozones, greater in the Prairies, and lower in the Pacific Maritime ecozone. Across sites, forage dry matter concentration was less for sweet pearl millet (289 g kg−1) and sweet sorghum (245 g kg−1) than for silage corn (331 g kg−1). Sweet pearl millet had a lower total digestible nutrient (TDN) concentration (452 g kg−1 DM) and aNDF digestibility (NDFd) than sweet sorghum and silage corn along with greater neutral detergent fibre (aNDF) and water-soluble carbohydrate (WSC) concentrations than silage corn. Sweet sorghum had greater aNDF and WSC, lower starch, and similar TDN (534 g kg−1 DM) concentrations, but greater NDFd compared with silage corn. Sweet pearl millet and sorghum fermented as well as silage corn, reaching low pH values and acceptable concentrations of lactic and volatile fatty acids. Sweet sorghum is therefore a viable alternative to silage corn in Canada except in the Pacific Maritime ecozone, but early-maturing hybrids with acceptable DM concentration at harvest are required.