Dietary protein in broiler feeds comes mainly from soybean meal and to a lesser extent from animal protein. Nowadays, animal protein is not recommended as a broiler feed ingredient because it is associated with zoonotic diseases such as salmonellosis and soybean is very scarce in Zimbabwe due to low productivity. This shortage is causing an increase in the cost of soybean and making broiler production less viable. Shortage of soybean is forcing animal nutritionists to search for potential alternative sources of protein. Cowpea is the best alternative since it is locally available, cheap and drought tolerant. Cowpea use in broiler feed manufacture is limited because it contains some anti-nutritional factors which reduce protein digestibility and broiler growth performance. The objectives of this paper are to determine the effectiveness of dehulling, roasting and boiling cowpea on nutrient and anti-nutrient content, protein digestibility and broiler performance. The purpose of this review paper is to develop cost effective broiler diets from cowpea. Protein digestibility was measured by using ecxreta analysis through subtracting protein in excreta from protein in feed ingested and broiler weight gains were measured by subtracting final bird weight from previous bird weight. Feed conversion ratio was calculated from dividing weight of total feed eaten by weight gained by the birds.

Poultry feeds are formulated using soybean meal and animal by-products as sources of protein. Animal proteins like fish meal, blood meal, meat and bone meal are being shunned in formulating poultry feeds nowadays because they are associated with zoonotic diseases like salmonellosis and this has left soybean meal as the only source of dietary protein in broiler feeds. Soybean meal is in short supply in Zimbabwe and this country is relying on some soybean meal imports from South Africa and Zambia resulting in prices of poultry feed and broiler meat going upwards. Cheap and locally available alternative sources of protein to soybean meal must be found in order to reduce the cost of making poultry feed. The selected alternative source of protein must have protein which is highly digestible such that the bulk of this protein can be metabolized and utilized by broilers to synthesize meat leaving a little of it to be excreted through faeces and urine. Highly digestible protein is very important in broiler feed making because this reduces the amount of nitrogen lost through poultry excreta into the environment. Cowpea has been chosen to entirely or partially replace soybean meal in this review paper because it is locally grown, drought tolerant, cheap and its true protein digestibility (TPD) of 71% to 76% is generally comparable to 81% to 83% of soybean meal. Nowadays, people are concerned about protecting the environment from being polluted by wastes from industrial and agricultural activities. Poultry farming pollutes the environment with ammonia emitted from poultry excreta. The grain legumes used in formulating broiler feed such as soybean meal contain anti-nutritional factors which reduce protein digestibility and increase nitrogen excretion through poultry faeces. The nitrogen in faeces is volatilized into ammonia, emitted into the atmosphere and cause eutrophication of surface How to cite this paper: Bumhira, E. and Madzimure, J. (2023) Effect of Incorporating Cowpea (Vigna unguiculata) Meal into Broiler Diets on Environmental Pollution by Nitrogen from Poultry Excreta: A Review.