Mortality rate in this study was within the recommended industry standards, that is, below 3% over the 35 d production period. Nonetheless, the sudden death noted in MH birds was in contrast to findings reported by Cruickshank (2001), wherein a soluble solution of twelve plant extracts was shown to improve performance and reduce ascites and necrotic enteritis in broilers. Sudden death (or flip over) is usually a result of increased blood flow due to the increased growth rate as a consequence of genetic selection, causing a strain on the heart, which is smaller in size as a percentage of live BW (Havenstein et al., 2003). Positive correlations have been reported between the heart and the carcass a trait, suggesting that as carcass yield increases, the heart weight also increases; however, this is not in response to selection, but nutrition (McEntee et al., 2001). Noteworthy was the increase in sudden death occurrence in birds fed MH grower and finisher diets in periods 15 to 21 d and 22 to 28 d, respectively, which seemed to be related to the increment in dietary MOLM supplementation. This effect may possibly be induced by the growth promoting effect in these leaves, which could also be the case in +C birds during period 29 to 35 d. Nevertheless, it is also suggested that broilers which are in good health may not respond to performance promoting additives if they are reared under optimal bio-security conditions (Bozkurt et al., 2012). Thus, the effects of optimal bio-security and sanitation measures that were in place in this study cannot be overemphasized for bird survival; this is depicted by the performance of birds fed −C diets comparable at certain instances to that of birds supplemented with antibiotics or M. oleifera leaves.