Características físicas, químicas e morfológicas em híbridos de urochloa diferidos

Abstract

Eight cultivars of Urochloa spp. (Sabiá, Dunamis, Mulato II, Mavuno, Ipyporã, Cayana, Cayman, and Camello) were recently released on the market. Understanding the chemical and physical characteristics of these hybrids under deferred conditions is essential to optimize pasture management and improve the nutritional value of tropical forages. Therefore, this study aimed to evaluate the morphological, chemical, and physical composition of the new deferred grasses and to verify whether there is a correlation between grinding resistance and the chemical and morphological characteristics of these forages. For this, forage mass samples were collected in 24 plots, distributed among the eight Urochloa hybrids. The experiment was conducted in a completely randomized design, with eight treatments (Urochloa hybrids) and three replications (plots). Grinding resistance (GR) was determined according to the method described by Hughes et al. (1998). Chemical analyses were carried out according to Detmann et al. (2021), with modifications based on Lourenço et al. (2017). Treatment means were compared using Tukey’s test for parametric analyses and the Kruskal-Wallis test for non-parametric analyses, considering a 5% significance level for type I error. There was a significant correlation (P<0.05) between GR and the contents of NDF (r=0.54) and ADF (r=0.46). However, there was no significant correlation (P>0.05) between GR and the other chemical analyses, which shows that samples with higher NDF and ADF contents are harder and more resistant to grinding. However, when analyzing fiber quality, this physical method does not adequately predict the material's quality, making it necessary to use other physical methods. Camello grass showed higher contents of Neutral Detergent Fiber (NDF), Potentially Digestible Neutral Detergent Fiber (pdNDF as %NDF), and lower Indigestible Neutral Detergent Fiber (iNDF as %NDF), while Cayman grass showed a higher percentage of iNDF along with Mavuno and Mulato II, and lower pdNDF content (%NDF; P<0.05). It is concluded that there is no correlation between GR and fiber quality parameters, making it an unsuitable physical method to infer such characteristics. Among the grasses studied, the Cayman hybrid showed the lowest nutritional quality under the adopted management, with higher iNDF content and lower pdNDF levels. Camello grass presented the highest NDF and pdNDF contents (%NDF), as well as the lowest iNDF content (%NDF), resembling Dunamis and Ipyporã grasses, and a higher percentage of dead stem, therefore this cultivar suggests potential for better forage utilization by animals.