Abstract: The effects of supplementation with urea molasses multi-nutrient blocks of dairy cows fed rice straw and green grasses on milk yield, composition, live weight change of cows and calves and intake were studied under village condition. The cows were offered 250 g UMMB per cow per day. The animal were divided into two groups and randomly assigned to two dietary treatments. The control group (A) received diet containing rice straw, green grasses, wheat bran, rice polish and mustard oil cake. However, the supplemented group (B) received UMMB in addition to normal diet, given to the control group. Supplementation of blocks to cows also receiving straw based diets increased milk production from 2.86 to 4.43 L/d (P<0.01) and live weight of calves from 20.29 to 25.57 kg (P<0.05). But did not significantly increased live weight, condition score, milk composition and intake of cows. This increase in milk yield is mainly explained by increased intakes of energy and nitrogen. UMMB was as recommended to be used as a strategic supplement in lactating dairy cows especially when fed on low quality roughages or crop residues.