RESUMO
ABSTRACT Sorghum is a crop that stands out as an alternative to corn due to lower soil fertility demand and increased tolerance to drought. Lack of information about the qualitative behaviour of sorghum hinders the recommendation of different purpose sorghum cultivars. The goal was to evaluate the chemical composition and in vitro digestibility of different purpose sorghum cultivar silages, at two cropping seasons. The trial was conducted at the Plant Production Department, Federal Institute of Education, Science and Technology of Rondônia, Colorado do Oeste campus, and chemical analyses and in vitro incubation were performed at the Laboratory of Animal Nutrition, Federal University of Mato Grosso, Cuiabá campus. The experimental design was a randomized block with a split-plot arrangement and four replications. Plot treatments consisted of six different purpose sorghum cultivars (BRS 308 and BRS 310, grain sorghum; BR 655 and BRS 610, forage sorghum; and BRS 506 and CMSXS 647, sweet sorghum). Split-plot treatments consisted of two cropping periods (first crop and second crop). Forage sorghum cultivar BRS 655 demonstrated higher non-fiber carbohydrate content and lower potentially digestible fibre content than the other cultivars did. Sweet sorghum cultivars had higher levels of water soluble carbohydrates and non-protein nitrogen based on protein, lower indigestible neutral detergent fibre content at second crop, and higher in vitro dry matter digestibility than the other cultivars. The silages of sweet sorghum cultivars BRS 506 and CMSXS 647, and forage sorghum cultivar BRS 655 presented higher nutritional values.
RESUMO O sorgo é uma cultura que se destaca como alternativa ao milho devido a menor exigência em fertilidade do solo e maior tolerância ao déficit hídrico. A falta de informações quanto ao comportamento qualitativo dificulta a recomendação de cultivares de sorgo de diferentes propósitos. Objetivou-se avaliar a composição bromatológica e a digestibilidade in vitro da silagem de cultivares de sorgo de diferentes propósitos, em duas épocas de cultivo. O delineamento experimental utilizado foi em blocos casualizados, com os tratamentos dispostos em esquema de parcela subdividida, com quatro repetições. Os tratamentos da parcela corresponderam a seis híbridos de sorgo de diferentes propósitos (BRS 308 e BRS 310, graníferos; BR 655 e BRS 610, forrageiros; BR 506 e CMSXS 647, sacarinos). Os tratamentos da subparcela corresponderam a duas épocas de cultivo (primeira safra e segunda safra). A cultivar de sorgo forrageiro BRS 655 apresentou maior teor de carboidratos não fibrosos e menor teor de fibra potencialmente digestível. As cultivares de sorgo sacarino obtiveram os maiores teores de carboidratos solúveis, os menores teores de fibra insolúvel em detergente neutro indigestível na segunda safra, e as maiores digestibilidades in vitro da matéria seca. As silagens de sorgo sacarino e de sorgo forrageiro BRS 655 apresentam maior valor nutritivo.
RESUMO
Our objective was to evaluate production, nutritive value and carrying capacity of piatã grass (Brachiaria brizantha cv. BRS Piatã), and performance of Nellore heifers in agrosilvopastoral systems (ASPS) with three eucalyptus (Eucalyptus urograndis) tree densities, during winter, spring, summer, and fall. Three integrated systems were evaluated: ASPS-1 (357 trees ha(-1)), ASPS-2 (227 trees ha(-1)), and CON (5 trees ha(-1)). In each system, two sward heights were evaluated: short and tall. A total of 80 11-month-old Nellore heifers were randomly allocated in a randomized split-plot block, 3 × 2 factorial. Greater dry matter availability was observed on CON pastures during the fall season. Greater percentage of leaf lamina was detected on ASPS-1 with short sward height and greater during summer, compared with other seasons. A greater forage production was observed between tree rows and for tall sward height. Spring was the season with less forage nutritive value. Average daily gain was greater during summer and fall. Gain per hectare and stocking rate were greater on CON system and on ASPS-2. Pastures with short sward height had greater gain per hectare and stocking rate. Agrosilvopastoral systems with intermediate tree density seem to be a good choice for producers willing to diversify their revenue sources without decreasing animal production.
