Woody plants are essential in ruminant nutrition in semi-arid regions particularly during the long dry season, however, their nutritional value varies considerably among species, seasons and geographical zones. A study was conducted to evaluate the seasonal variation in chemical composition and in-vitro gas production of woody plant leaves and their relationship. Leaves from sixteen (16) major plant species utilized by livestock were collected from six constituencies of Namibia in the wet season (January: summer), early-dry (May: winter) and late-dry (September: spring) season. There were significant influences of seasonal variations on dry matter (DM), ash, neutral detergent fibre (NDF) and soluble tannin (ST) concentrations of the plant species (p < 0.05). However, crude protein (CP) and acid detergent fibre (ADF) were not affected by season (p > 0.05). Rhigozum trichotomum (900 ± 13.9 g/kg), Vachellia hereroensis (902 ± 13.8 g/kg) and Baphia massaiensis (910 ± 13.2 g/kg) had lower DM content during the late-dry season as compared to wet and early-dry season. The NDF content was highest in Grewia bicolor (610 ± 48.1 g/kg DM) in the wet season and lowest in Vachellia mellifera (232.0 ± 41.5 g/kg DM) in the early-dry season. Seasonal variation influenced the rate of degradation but not the potential gas production, however, the species were not significantly influenced by seasonal variation for the parameters measured. Species with higher gas potential showed lower rates of degradation (r = − 0.71, p < 0.01). Though the chemical composition of the species was poorly correlated (p > 0.1) to the in-vitro gas production parameters, a positive correlation existed between ST and degradation rate (r = 0.52; p < 0.01). Seasonal variation influences the quality of woody plants and therefore, their leaves should be harvested during their optimal nutritious stage to improve livestock productivity.

木本植物对半干旱地区的反刍动物营养至关重要，特别是在漫长的旱季，然而，它们的营养价值因物种、季节和地理区域而异。进行了一项研究，以评估木本植物叶片化学成分和体外产气量的季节性变化及其关系。在湿季（1 月：夏季）、早干（5 月：冬季）和晚干（9 月：春季）季节从纳米比亚的六个选区收集牲畜利用的十六 (16) 种主要植物物种的叶子。季节性变化对植物物种的干物质 (DM)、灰分、中性洗涤纤维 (NDF) 和可溶性单宁 (ST) 浓度有显着影响 ( p < 0.05)。但粗蛋白（CP）和酸性洗涤纤维（ADF）不受季节影响（p  >0.05）。Rhigozum trichotomum（900±13.9克/千克），Vachellia hereroensis（902±13.8克/ kg）和Baphia massaiensis（910±13.2克/ kg）作为比较湿和早期干有后期旱季低DM含量季节。NDF含量在雨季以Grewia bicolor（610±48.1 g/kg DM）最高，在Vachellia mellifera最低(232.0 ± 41.5 g/kg DM) 在早旱季。季节性变化影响降解率，但不影响潜在的天然气产量，然而，物种不受测量参数季节性变化的显着影响。具有较高气体潜力的物种表现出较低的降解率（r = - 0.71，p  < 0.01）。尽管该物种的化学成分与 体外产气参数的相关性较差 ( p > 0.1)，但 ST 与降解率之间存在正相关性 (r = 0.52；p  < 0.01)。季节性变化会影响木本植物的质量，因此，应在最佳营养阶段收获其叶子，以提高牲畜生产力。