ENSILING PROPERTIES OF SWEET SORGHUM

Sweet sorghum [Sorghum bicolor (L.) Moench] cultivars have been bred f or high sugar content; with accompanying adequate forage yield, the cr op may offer potential for ensiling. ''Wray'' sweet sorghum, a good su gar producer, was grown under field conditions to determine nutritiona l quality and subsequent animal performance of silage from the yield. In one experiment, ''Wray'' was compared to ''FS-5'', medium-tall fora ge sorghum, at four reproductive stages of growth, in regard to agrono mic characteristics and chemical composition. In another study, the '' Wray'' sweet sorghum was harvested in early and late reproductive stag es and stored in experimental silos. Ensiling losses were measured; in addition, the silages were offered to sheep to determine in vivo dige stibility (IVODMD) and intake. In the first experiment, dry matter yie lds of both sweet and forage sorghum increased during the reproductive period, from 6.2 to 11.9 and 7.7 to 13.9 Mg/ha, respectively; at matu rity, grain yields were 651 and 3,526 kg/ha, respectively. Total avail able carbohydrates tended to be higher in the forage type (23.4%) than in the sweet sorghum (19.9%). Average in vitro dry matter disappearan ce (IVDMD) was similar for both sorghums at 60.2%, but sweet sorghum I VDMD tended to be higher than forage sorghum at the hard dough stage ( 61.4 versus 55.1%) . In the second experiment, intake was greater when lambs were offered hard-dough stage silage (1,240 g/lamb/day) versus bloom-stage silage (878 g/lamb/day), even though IVODMD was similar (a verage 60.6%) at both harvest stages. The silages appeared to be prope rly ensiled, as silage pH was less than 4.0; however, effluent and dry matter losses were greater with bloom-stage silage. These differences probably were due to the slight dry matter differential between the t wo (22.3 and 26.6%, respectively). To maximize yield, sweet sorghum sh ould be ensiled at the hard-dough stage. Resulting silage may be highe r in digestible dry matter than that of medium-tall forage sorghums, w hich produce grain.