Research note: The silage characteristics of two varieties of forage sorghum mixed in different proportions and at two stages of maturity

Two varieties of forage sorghum, low grain Dekalb FS‐5 (FS) and higher grain Pioneer 947 (GS) were harvested at the milk and dough stages of maturity respectively. Each variety was ensiled separately and as mixtures under laboratory conditions. The mixtures comprised FS.GS at ratios of 3:1 and 1:1 respectively. At the milk stage the FS had a dry matter (DM) content of 338 g kg−1 and water‐soluble carbohydrates (WSC) content of 120 g kg−1, as compared with 389 g kg−1 and 63 g kg−1, respectively for the GS. At the dough stage, these contents were 374 g kg−1 and 123 g kg−1 for the FS, and 520 g kg−1 and 29 g kg−1 for the GS, respectively. At the dough stage the GS had higher neutral detergent fibre (NDF) and acid detergent fibre (ADF) contents than FS (592 g kg−1 and 379 g kg−1 vs. 533 g kg−1 and 339 g kg−1 DM, respectively). In the silage harvested at milk stage, the pH of FS alone decreased most slowly, whereas at the dough stage the pH of the GS remained highest. In mixtures the pH decline accelerated with an increasing proportion of FS. Following harvest at the milk stage the 3:1 (FS:GS) had the best ensiling characteristics, whereas following at the dough stage the 1:1 mixture provided the most stable silage. Rumen degradability of the silage of GS was higher than that of the FS silage, especially for material harvested at dough stage of maturity (59.2 g kg−1 vs. 50.9 g kg−1). Mixing FS with GS at the ensiling increased the digestibility of the resulting silage as compared with FS alone.