The nutritional profile of ripe and abscised unripe mango fruits of Alphonso, Mabrouka, and Zill varieties have been reported. This has created a paucity of information on the nutritional quality of the fruits, especially the unripe mango fruits, which are potential dietary ingredients for livestock. Hence, this study evaluated the in vitro gas production, methanogenesis, in vitro dry matter degradability, and rumen metabolites of ripe and abscised unripe mango fruits of the Alphonso, Mabrouka, and Zill varieties. The treatments comprised forage (control), unripe Alphonso, ripe Alphonso, unripe Mabrouka, ripe Mabrouka, unripe Zill, and ripe Zill mango fruits in a CRD. The data were analysed using a general linear model of ANOVA, while significant means were compared using DMRT. The results showed that the total gas production (TGP) and in vitro dry matter degradability (IVDMD) of ripe and abscised unripe mango fruits of Alphonso, Mabrouka, and Zill varieties were similar and higher (P<0.05) than the forage. The percentage of CH4 to gas production, TGP/IVDMD, and CH4/IVDMD were higher (P<0.05) in the forage than the ripe and abscised unripe mango fruits of the three varieties. The ruminal pH levels were lower (P<0.05) in mango fruit treatments compared to the forage, while the ripe mango fruit of the Zill variety had significantly higher (P<0.05) volatile fatty acids (mmol/L) and propionic acids, but lower acetic acids production than the forage. There was no difference (P>0.05) observed in the ruminal NH3-N (mg/dL), butyric acid, and iso-butyric acid production among the forage and the mango fruits of the three varieties. The gas production at 3 hours for both the ripe and the unripe mango fruits of the three varieties was higher (P<0.05) than the forage. However, at 24 hours, the gas production of the forage was only lower (P<0.05) than the ripe Alphonso and Mabrouka, while at 48 hours, no difference (P>0.05) was observed in the gas production of the forage compared to the mango fruit treatments. It can be concluded that abscised unripe mango fruits of Alphonso, Mabrouka, and Zill varieties possess competitive nutritional quality to the ripe mango fruits, outperforming the forage as both livestock and climate-smart dietary ingredients. Also, variety had no effect on the in vitro gas production, dry matter degradability, and methanogenesis of mangos for both the ripe and abscised unripe fruits. It is therefore recommended that the nutritional quality and methane-producing potential of abscised unripe mango fruits of the Alphonso, Mabrouka, and Zill varieties be evaluated in vivo.