REGULAR ARTICLES Change in growth performance of crossbred (Ankole×Jersey) dairy heifers fed on forage grass diets supplemented with commercial concentrates Mupenzi Mutimura 1,2 & Cyprian Ebong 2 & Idupulapati Madhusudana Rao 3 & Ignatius Verla Nsahlai 1 Received: 28 July 2015 /Accepted: 11 February 2016 /Published online: 18 February 2016 # Springer Science+Business Media Dordrecht 2016 Abstract Rearing heifers for dairy cow replacement is a chal- lenge in smallholder dairy farms in the tropics due to feed shortage. The objective of this study was to evaluate Brachiaria hybrid cultivar Mulato II as a forage resource for improving growth performance of dairy heifers under cut-and- carry feeding system in Rwanda. Sixteen crossbred (Ankole × Jersey) heifers (mean weight 203 ± 35 kg) were ran- domly allocated to two dietary treatments viz: Mulato II with 2 kg/day of commercial concentrates (MCC) and Napier grass (Pennisetum purpureum) with the same supplement (NCC), for a period of 12 weeks. Mineral lick and water were provid- ed ad libitum. Daily feed intake and fortnightly live weight were measured. Average daily gains and feed conversion ratio (FCR) were calculated. Results showed that absolute daily dry matter intake (g DMI/day) and relative intake (g/kg of meta- bolic body weight—BW 0.75 ) were higher in heifers fed on MCC than in heifers fed on NCC (P < 0.001). FCR was lower (P < 0.001) in MCC than NCC diets. Final body weight (FBW) and body weight gain (BWG) did not differ between the two groups of heifers (P >0.05). Average daily weight gain (ADWG) also not differed significantly (P > 0.05). Based on numerical body weight changes and nutritive values, Mulato II showed potential to be integrated into local cut-and- carry feeding systems for better heifer rearing to facilitate dairy cow replacement. Keywords Dry matter and nutrient intake . Feed conversion ratio . Brachiaria grass . Napier grass Introduction Population growth and shrinking of grazing land have com- pelled farmers to shift from extensive to intensive dairy sys- tem in order to optimise milk yield per cow (Lukuyu et al. 2012). In spite of the additional stress on limited feed re- sources, especially during the dry season, farmers retain fe- male calves to replace culled cows (Mohd Nor et al. 2015). In tropical areas of Asia, Africa, and South American highlands, farmers lose replacement dairy stock due to limited knowl- edge on calf and heifer rearing. Approximately 35 % of the losses can be restored using adequate feeding (Moran 2011). In these areas, Napier grass (Pennisetum purpureum) is the most abundant single, year-round feed resource in smallholder dairy farms (Rahman et al. 2015; Mutimura et al. 2013). However, total dependence of farmers on Napier grass is risky because of Napier stunt disease that poses threats to the pro- duction of this grass throughout the East African region (Asudi et al. 2015). Developing disease resistant cultivars has been identified as one possible approach to address the problem (Kawube et al. 2014). However, there is need to consider alternative fodder species to complement the search for disease resistance in the global germplasm collection and local landraces. Brachiaria species are indigenous grasses to Africa, which have been selected for productivity and tolerance to abiotic and biotic stresses in Latin America (Miles et al. 2004). * Mupenzi Mutimura mmutimura@yahoo.co.uk 1 School of Agricultural, Earth and Environmental Sciences, Department of Animal and Poultry Science, University of KwaZulu-Natal, Pietermaritzburg Campus, Private Bag X01, Scottsville 3209, South Africa 2 Department of Animal Production, Rwanda Agriculture Board (RAB), P.O. Box 5016, Kigali, Rwanda 3 International Center for Tropical Agriculture (CIAT), A.A. 6713 Cali, Colombia Trop Anim Health Prod (2016) 48:741–746 DOI 10.1007/s11250-016-1019-4