ALBERT

Description: The study aimed to examine the effects of harvesting three maize hybrids at different maturity stages on the ruminal fermentation kinetics, fermentation end-products (volatile fatty acid, ammonia and methane) output, and digestibility of maize plant fractions, as well as the degradability of the resulting silage. Three hybrids were compared (Maximus VIP3, Defender VIP and Feroz VIP) harvested at three grain maturity stages (milk (R3), dough (R4) and dent (R5) grain), while silage samples were collected only at the dent grain stage (R5). Grain digestibility tended to decrease as the maturity stage progressed (p 〈 0.05), while the whole-plant digestibility increased with increasing maturity for the three evaluated hybrids (p 〈 0.05). The gas production of whole-plant at 24 h of incubation was higher for the Maximus hybrid than for the others (p 〈 0.05), with average values of 188, 196 and 207 mL g−1 dry matter at stages R3, R4 and R5, respectively. For the in situ ruminal degradation kinetics of silage, instantly degradable dry matter and fiber potential degradability were greater with Maximus maize forage than with the other two hybrids. From the perspective of in vitro results, the Maximus VIP3 hybrid seems to be the most suitable for silage production when harvested between the dough and the dent grain stage of maturity.

Description: The chemical composition of plant components of three maize hybrids harvested at the beginning of six reproductive stages of maturity was compared. The hybrids evaluated included Maximus VIP3, Defender VIP and Feroz VIP, which were evaluated at each of following stages: R1 (grain formation), R2 (milky grain), R3 (pasty grain), R4 (floury grain), R5 (hard grain) and R6 (ripe grain). The advancement in maturation was linearly related to the crude protein (CP) content of the stem, whole plant, and leaves, and there was a difference among the hybrids. Between R4 and R5 stages, Maximus and Defender presented the highest CP contents for husk (6.58 and 5.42% for Maximus; 5.54 and 5.17% for Defender). The neutral detergent fiber (NDF) of the leaves showed a quadratic relationship with the advancement of maturation but did not differ among the hybrids. For all the hybrids, the NDF content in the husk and cobs increased linearly during the reproductive stages (〉77 and 78%, respectively, for the three hybrids in R6). Defender had the lowest NDF content of the cob in R3. The acid detergent lignin contents did not differ among stages in the stems, and showed a linear decrease throughout the whole plant, though the contents did not differ among the hybrids. Due to the differences observed, recommendations for harvest based on the maturity stage for each hybrid should be taken into consideration. There seems to be no important distinction among hybrids for harvesting and use of straw. Despite the reduction in grain yield, an early harvest for earlage or snaplage can provide lower lignin content in husk and cob, as well as higher protein content in the husk, favoring the nutritional value of the vegetative fraction (husk and/or cob).