Corea-Guillen et al., 2025. Ital. J. Anim. Sci., 24(1): 2334-2345

This study evaluated the effect of partially replacing corn silage (CS) with napier grass silage (NS) in dairy cow diets on nutrient utilisation and performance. Eighteen lactating Holstein cows (BW 533 ± 58 kg; DIM 91 ± 41 d; MY 23.9 ± 3.4 kg/d) were allocated to two groups of nine in a crossover design. The CS diet contained 400 g/kg DM of CS, while the NS diet contained 300 g/kg DM of NS and 100 g/kg DM of CS. Both diets also included 80 g/kg of napier grass and 20 g/kg of Swazigrass. The experiment consisted of two 21–day periods, comprising 15 days of adaptation and six days of sampling. Feed, refusals, faeces and milk samples were taken for nutrient analysis and urine samples were taken for nitrogen and purine derivatives analysis. Intake and digestibility of DM, OM, CP, NDF and ADF, as well as milk yield and composition, nitrogen excretions and microbial protein synthesis (MPS), were estimated. Cows fed NS had greater daily DM intake (20.4 vs 19.5 kg), OM intake (18.2 vs 17.5 kg), CP intake (3566 vs 3420 g) (p < 0.05), greater DM digestibility, OM digestibility, NDF digestibility, ADF digestibility (p < 0.05), and MPS (1820 vs 1574 g/d, p < 0.05). Napier silage also increased lactose concentration and yield. Replacing partial CS with NS in the diet of dairy cows increased intake and digestibility of nutrients and MPS, with no detrimental effect on milk yield or composition.