Global human population growth, increased income, and the demand for quality protein by people for good health and wellbeing are increasingly becoming key drivers for higher animal protein production (OECD-FAO, 2016). Annual per capita consumption of meat is projected to reach 35.5 kg and 88 to 100 kg per person in developing and developed countries respectively by 2025 (OECD-FAO, 2016). The increase in the demand for animal protein has challenged geneticists, nutritionist and meat producers to focus on producing animals within the least possible time (Raha, 2007). Consequently, poultry, especially broilers, are becoming more dominant within the meat complex. The short production cycle has enabled rapid responses to market signals by producers, whilst allowing for expeditious improvements in genetics, animal health, and feeding practices. Nevertheless, under commercial broiler production, one of the major drawbacks has been the increasing cost of feeds which can take as much as 70% of the total cost of production (Disetlhe et al., 2018). In particular, the protein and energy components of the broiler diets are becoming rather expensive and scarce due to factors that include increased pressure on land footprint, recurring droughts and climate change that have resulted in reduced production, culminating in intense competition between humans and livestock for the same feed (Mengesha, 2012). Khan et al. (2009) opined that scarcity and high price of good quality feed, especially protein and energy rich feed ingredients, are one of the most important constraints to the improvement and sustenance of broiler productivity.
The higher prices of poultry feed ingredients have provoked intense efforts by nutritionists in seeking alternative ingredients that optimize broiler production at a lesser cost (Babiker, 2012; Moreki and Gabanakgosi, 2014). As a result, Müseler and Schönfeldt (2006) recommended the investigation of little-known but high potential plant feed sources which are native to dry areas requiring little seasonal rainfall. Among other native plant feed sources, marama bean (Tylosema esculentum) has been shown to have great potential as a protein source. Marama bean is a protein rich legume that thrives in arid and semi-arid regions with feasible agronomic and economic returns. The plant has been observed to have nutrient composition similar to that of peanuts (Arachis hypogaea) and soybeans (Glycine max) (Tibe et al., 2016; Keegan and van Staden, 1981) and thus has the potential to replace conventional protein ingredients in poultry diets. Marama contain approximately 34.1% crude protein and 33.5% oil, respectively (Amarteifio and Moholo, 1998). Although the protein is low in the essential sulphur-containing amino acids; methionine and cysteine, it has adequate level of lysine. Lysine is considered the first limiting amino acids in poultry diets and hence its inclusion in diets may reduce the amounts of additional elementary lysine during diet formulation (Siqueira et al. 201; Nasr and Kheiri, 2012).
Although there are many non-conventional feeds such as marama bean with substantial nutritional value and inexpensively available in large quantities, their inclusion in formal animal feed database and feed formulation systems is being limited by the lack of adequate nutritional information (Olukosi et al., 2019; Usayran et al., 2014). The nutritional potential of marama bean as food for humans has been investigated in a number of studies (Bower et al., 1988; Müseler and Schönfeldt, 2006). However, no studies have been done on the value of this plant as feed for livestock particularly poultry. Some research exploring the use of diets containing non-conventional feed ingredients as protein sources reported positive responses on growth performance and carcass quality of broilers (Olukosi et al., 2019; Usayran et al., 2014). We therefore postulate that marama bean may be included in broiler diets without negative effects on performance. The study was hence conducted to assess the effects of inclusion of marama bean in broiler diets on growth performance, protein utilisation and physiological responses.