Caracterização químico-bromatológica, digestibilidade e produção de gases in vitro da palma forrageira dos gêneros Opuntia e Nopalea em diferentes estádios fenológicos

Abstract

The aim of this study was to evaluate the chemical composition, digestibility and in vitro gas production of forage palm of the genus Opuntia and Nopalea in different phenological stages. Three genotypes of forage palm of the genus Opuntia (IPA-200024, IPA- 10002 and IPA-20001) and onde genotype of the genus Nopalea (IPA-200206) were evaluated, in a completely randomized experimental design and a 4 x 3 factorial scheme, corresponding to 4 genotypes and 3 phenological stages, with 4 replicates. The study was carried out at the Experimental Station of the Instituto Agronômico de Pernambuco-IPA, located in the county of Arcoverde - Pernambuco. Four plants of each variety were selected and the selection of cladodes in different phenological stages (young, intermediate and mature) was carried out, followed by chemical analyzes, digestibility and in vitro gas production. There were no differences (P>0.05) in the dry matter (DM) content in all varieties studied, with phenological stages influencing (P>0.05) only the genotype Copena F1, in the content of crude protein (CP). F24 and Orelha de Onça differed with each other (P<0.05), with levels of 60.3 and 34.4 g kg-1 MS respectively. The other variables differ (P<0.05) only at the young stage. In the fibrous compounds, there was a difference (P<0.05) in the content of neutral detergent fiber (NDF) in all varieties with no influence of phenological stages (P>0.05) only for the genotype F24. The phenological stages influencend (P<0.05) on content of acid detergent fiber (ADF) only the Orelha de Onça variety, and the lowest value was observed at the young stage with 96.9 g kg-1 MS. The content of acid-digested lignin (ADL) and pectin (PEC), the Orelha de Onça genus presented the smallest value at the young stage with 3.1 g kg-1 MS and higher intermediate value at 181.7 g kg-1 MS respectively. Was observed a difference (P<0.05) on the content of hemicellulose (HEM) and cellulose (CEL) only in the mature stage for HEM and young and intermediate stages for CEL. The Orelha de Onça genus had a higher concentration of non-fibrous carbohydrates (NFC) with 702.9 g kg-1 and in fraction B2 the lowest concentration was 150 g kg-1, all at the young stage. In the others variables there was difference (P<0.05) among the studied genotypes. In the digestibility parameters there was a difference (P<0.05) between the genotypes and the phenological stages (P>0.05). The phenological stages influenced all the genotypes except15 F24. In the gas production characteristics, there was no difference (P> 0.05) in the degradation rate parameter (A + B1), with the highest volumes of total gas production (Vt1) observed for Orelha de Onça genotype 333.86 mL g-1 MS. Among the genotypes, Orelha of Onca was the one that was less prominent in relation to FC and PEC, and stood out by the NFC, which influenced the kinetics of in vitro gas production, showing a greater availability of nutrients in the rumen. The phenological stages of forage palm genotypes did not influence DM in vitro digestibility.