Forage Nutrient Fluctuations During the Dry Season: A Case Study of Tropical Grazing Land in East Nusa Tenggara, Indonesia

Natural grazing land plays a crucial role in extensive ruminant livestock systems, especially in semi-arid tropical regions such as East Nusa Tenggara (ENT), Indonesia. The availability and quality of forage during the dry season present significant challenges. This study aimed to identify variations in grass species composition and fluctuations in forage nutritional content in natural grazing lands of ENT during the dry season (July–October 2024). Sampling was conducted in four sub-districts: two representing lowland zones and two representing highland zones. In each sub-district, four grazing fields were selected, and ten plots were sampled per grazing field, totaling 160 sampling plots. Species identification and nutrient analysis included crude protein, crude fiber, energy content, and protein-energy ratio. Statistical analyses using ANOVA and Tukey’s multiple comparison test were performed to evaluate significant differences in nutritional parameters across months and zones. Dominant species identified were Themeda arguens, Heteropogon contortus, Brachiaria decumbens, Ischaemum timorense, Cynodon dactylon, and Pennisetum clandestinum. Results showed significant monthly fluctuations in crude protein and fiber contents (p < 0.05), with protein levels decreasing from July (9.31 ± 2.66%) to October (7.53 ± 3.10%). Energy content and protein-energy ratio also varied significantly across the dry season. A monthly shift in dominant grass species composition was observed, influenced by environmental conditions and species adaptability. The protein-energy ratio of forage remained below optimal levels throughout the dry season, potentially limiting livestock productivity. These findings provide important scientific insights for developing climate-resilient feeding strategies and support policy formulation for sustainable tropical livestock farming in semi-arid regions.