Genetically engineered alfalfa (Medicago sativa L.) cultivars with reduced lignin (RL) concentration are commercially available but their change in nutritive value as the crop matures within a growth cycle has not been thoroughly documented and might differ from non‐RL cultivars. This research documents changes in forage nutritive value of a RL cultivar (HarvXtra‐008) and two non‐RL cultivars (54R02 and WL355RR) within five growth cycles across 2 yr in six states in the United States. A randomized complete block design with a split‐plot arrangement of treatment randomization was used, with harvest growth cycles assigned to whole plots and cultivars to subplots in field trials. Cultivars were sampled on 3‐ to 4‐d intervals between day 20 and 37 of regrowth. HarvXtra‐008 was consistently lower (P ≤ .05) in acid detergent lignin (ADL) by 7–10% and amylase‐treated neutral detergent fiber (aNDF) by 2–10% and 4–9% greater (P ≤ .05) in neutral detergent fiber digestibility (NDFD) than non‐RL cultivars across all sampling dates. Cultivar × regrowth duration interactions (P ≤ .05) were found only for ADL and aNDF in two of the five growth cycles sampled, when regression coefficients were always smaller for HarvXtra‐008 than 54R02. We calculated that the interval between harvests can be extended on average from 8 to 11 d for HarvXtra‐008 compared with non‐RL cultivars while maintaining adequate fiber digestibility for animals with high nutritional requirements; however, the extent of that longer harvest interval varied from 2 to 20 d depending on environmental conditions.

中文翻译：

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再生期木质素苜蓿草料营养价值的变化

降低木质素（RL）浓度的转基因苜蓿（Medicago sativa L.）品种在市场上有售，但随着作物在生长周期内成熟，其营养价值的变化尚未得到充分记录，并且可能与非RL品种不同。这项研究记录了美国六个州RL品种（HarvXtra-008）和两个非RL品种（54R02和WL355RR）在2年的五个生长周期内其饲料营养价值的变化。采用随机全区组设计和处理分配的随机分布，在田间试验中，将收获生长周期分配给整个地块，将栽培品种分配给子图。在再生的第20天到第37天之间以3-4天的间隔对品种进行采样。HarvXtra-008始终较低（P≤0.05）木质素（ADL）7-10％和淀粉酶处理过的中性去污剂纤维（和f）2-10％和4-9％的酸性洗涤剂（P在中性洗涤剂纤维消化率≤0.05）（NDFD ），而不是在所有采样日期中都使用非RL品种。品种×再生持续时间的相互作用（P ≤0.05）仅发现于ADL和ANDF两个五个生长周期的采样，当回归系数总是较小为HarvXtra-008比54R02。我们计算出，与非RL品种相比，HarvXtra-008的收获间隔平均可延长8到11 d，同时对营养要求较高的动物保持足够的纤维消化率。然而，根据环境条件的不同，更长的收获间隔的范围从2天到20天不等。