Chemical composition and in vitro digestibility of stalks, leaves and cobs of four corn hybrids at different phenological stages

Abstract

Four hybrids of class FAO 700: EA6601 and Simeto (Monsanto), Eleonora (Pioneer), Pampero (Syngenta), grown under identical conditions, underwent analysis to determine their analytical and botanical composition and DM (IVDMD) and NDF (IVNDFD) in vitrodigestibility. The content of fibrous fractions increased with maturity. For stalks there was an increase from an average value of 47.72% (V8) up to over 61% during the dough stage of the grain (R4) reaching over 73% during the phase of physiological maturation (R6). At the eighth-leaf vegetative stage in hybrids the stalk represent- ed 61.59% of the DM of the plant and reached 40.35% in the dough stage, while the leaf apparatus fall from 38.41% of the eighth-leaf stage DM to 18.19% during the dough stage of the grain and only 9.17% during physiological maturation. The ear, which represented only 12.93% of DM plant at the silking stage, increased to 41.47% and 53.01 respectively at the dough and physiological phases. At the dough stage (R4) the hybrids Simeto and Pampero, had a stalk percentage significantly higher (41.67% and 42.34% respectively; P< 0.01) compared with Eleonora (38.97%) and EA6601 (38.44%). Eleonora hybrid had a leaf proportion of 19.80% - higher than Pampero (17.93%), Simeto (17.60%), EA6601 (17.43%). This greater leafiness occurred with a lower incidence of the stalk, which has the highest loss of digestibility during maturing. The grain percentage of EA6601 was significantly higher than Pampero (26.46%), Simeto (27.33%) and Eleonora (27.88%). In the R4 phase the hybrid EA6601 had a higher stalk fibre content (ADF 41.38%; P< 0.05) compared to Pampero (37.61%) Simeto (38.14%) and Eleonora (39.16%). The effect of the phenological stage on the fiber content of the leaves was less evident, only the ADL increased from values of about 5% in the first period, to 8% and more in the final three stages. Even here, in dough stage, EA6601 differed (P< 0.01) from the others for its higher levels of ADL (9.35%) and ADF (35.05%), while the hybrids Eleonora and Pampero presented lower values of ADL (P 0.01) and ADF (7.90%). Simeto had the lowest ADF content (31.39%; P< 0.01). In the dough stage there was no significant differ- ences for in vitrodigestibility of DM and NDF between the hybrids - for all the botanical parts. In the whole plant, as maturity advanced, the differences of in vitrodigestibility of stalks, were counterbal- anced by the increasing proportion of grain.

Keywords

• Corn silage, Hybrids, Digestibility, Plant composition