Feeding guides for animals are based on body weight Advisory service providers often depend on Heart Girth (HG) and Body Conditions Scores (BCS) as proxy indicators of Live Body Weight (LBW) in mature cattle. But the relationship is affected by a number of factors including breed, parity and physiological status of the animal. There is a tacit gap in understanding the relationships between BCS and LBW and their implications on animal management decisions in developing countries including Rwanda. A study was therefore conducted to determine the effect of genotype and parity on the relationship between BCS and LBW in lactating Ankole cows and their crossbreds with Friesian genotypes. Results revealed that BCS and LBW were more correlated (r≥0.90) in Ankole than in crossbred cows (r≤0.40). The correlation improved the correlation to similar levels in all breeds (r≥0.90) when parity was considered independently. The cows gained 11 -20 kg/Unit BCS because of low frame size. It was concluded that BC Systems were pertinent management tools for developing countries and the relationships between BCS and LBW could be an important selection tool for dairy cattle improvement in Rwanda.