Improved cultivars (cvs.) of Brachiaria hybrid and Pennisetum purpureum forages have been studied extensively in research settings but still there is a paucity of information about their on-farm performance. This study was therefore set to evaluate the on-farm performance of Brachiaria hybrid cvs. Cayman and Cobra, and Pennisetum purpureum cvs. ILRI 16835 and Ouma in the Southern Highlands of Tanzania. A total of 30 smallholder dairy farmers who cultivated these improved forage grasses were involved in this study. A 2 m × 2 m sub-plot was marked in established pasture plots and a standardised cut at a 5–7 cm stubble height was done at the beginning of this study. The forage growth performance was conducted from April–July, 2021 (dry period) in two phases of 6 weeks each. These cultivars were evaluated for their above-ground growth performance and nutritional values at the end of each phase. Plant height, leaf length, leaf widths, and number of tillers per plant among cultivars varied significantly (p < 0.05) while above-ground forage biomass did not vary among cultivars (p > 0.05). Crude protein values did not vary significantly among cultivars (p > 0.05), they were 131–141 g kg−1 dry matter (DM). These values were not able to meet the nutritional requirements of the lactating dairy cow. Brachiaria hybrid cv. Cayman had the lowest (p < 0.05) neutral detergent fibre (NDF, 539 g kg−1 DM) compared to other cultivars (545–571 g kg−1 DM), hence high digestibility. It was concluded that Cayman was the best cultivar for forage production in the Southern Highlands, Tanzania due to its low NDF content. However, lower biomass warrants mixing of Cayman with other feeds to meet the daily requirements of a lactating dairy cow.
