Cutting ages of elephant grass for chopped hay production1

ABSTRACT With the advancement of the cutting age, there is an increase in the forage yield of elephant grass (Pennisetum purpureum), but there is also a reduction of the protein levels and digestibility of this forage. This study aimed to identify the ideal cutting age of elephant grass forage (BRS Canará cultivar) to chopped hay production. The experimental design was a randomized block, with five treatments (42, 60, 76, 91 and 105 days of growing) and four replicates. Forage agronomical, morphological and chemical characteristics were evaluated. A linear positive effect of the cutting age was observed on plant height, senescent material and yield of the chopped hay. The leaf percentage and leaf:stem ratio were reduced by the advance in the cutting age. There was also a linear positive effect of the cutting ages on indigestible neutral detergent fiber, neutral detergent fiber corrected for ash and protein and neutral detergent insoluble protein, with increases of 17.13 %, 16.63 % and 20.66 %, respectively. The contents of ashes, crude protein, total digestible nutrients and net lactation energy were reduced with the advance in the forage age. From 76 days, the ashes contents reached values below 9.29 % and the crude protein below 7.16 %. In the same cutting age, the chopped hay yield was 12.91 t ha-1. To improve the hay quality and production, the BRS Canará cultivar must be harvest between 60 and 76 days, when the plants are with 1.20-1.50 m of height, leaf:stem ratio of 0.55-0.44, crude protein of 8.29-7.16 % and indigestible neutral detergent fiber of 26.21-29.06 %.

摘要 随着刈割生育期的延长，象草（Pennisetum purpureum）的饲草产量有所提升，但该饲草的蛋白质含量与消化率却出现下降。本研究旨在明确用于制作碎干草的象草BRS Canará品种的最优刈割时期。试验采用随机区组设计，设置5个处理（生育期分别为42、60、76、91和105天），4次重复。对饲草的农艺性状、形态性状及化学组成进行了测定。研究发现，刈割生育期对株高、枯落物占比及碎干草产量均存在线性正向影响。随着刈割生育期的延长，叶片占比与叶茎比均逐渐降低。此外，刈割生育期对中性洗涤不消化纤维、经灰分与蛋白质校正的中性洗涤纤维及中性洗涤不溶性蛋白含量亦存在线性正向影响，增幅分别为17.13%、16.63%和20.66%。灰分、粗蛋白质、总可消化养分及泌乳净能含量则随饲草生育期的延长而降低。当生育期达到76天时，灰分含量降至9.29%以下，粗蛋白质含量降至7.16%以下。该刈割时期下，碎干草产量可达12.91吨/公顷。为兼顾干草品质与产量，BRS Canará品种应于60~76天生育期时进行刈割，此时植株株高为1.20~1.50米，叶茎比为0.55~0.44，粗蛋白质含量为8.29%~7.16%，中性洗涤不消化纤维含量为26.21%~29.06%。