1.1 Background Information
High cost of feed emanating from volatility in the macro environment and general unavailability of feed or high cost of feed ingredients, especially protein sources has resulted in declining productivity and profitability for intensive broiler production system. This Scenario has resulted in supply bottlenecks forcing an upsurge in the price of broiler products in Nigeria. Given the central importance that feeds play in intensive broiler system it becomes imperative to identify other feed ingredients of lower cost and sound biological values that can partly supplement the conventional protein sources in broiler diets.
The use of local, cheap and readily available materials particularly those that are not readily utilized by man has received particular attention as the only viable alternative to the use of conventional feedstuffs (Nwakpu et al., 2000; Ekenyem, 2006; Odunsi, 2003). This is as a result of the fact, that, the price of the conventional protein sources have soured so high in recent times, due to stiff competition between the Nigerian feed industry and man for the utilization of conventional ingredients such as groundnut, soyabean, fish meal etc. hence, call for investigation of this cheap, non conventional feed resources.
The protein from leaves may be recovered and fed to farm animals in form of leaf meal protein concentrates (Farinu et al., 1992). Leaf meal made from fodder shrubs is helping small – scale farmers in Tanzania to boast their income (WAC, 2006). Leaf meal does not only serve as protein source but also provide some necessary vitamins, minerals and also oxycarotenoids which cause yellow colour of broiler skin, shank and egg yolk (D’Mello et al., 1987; Opara, 1996).
Among tested leaf meals in poultry nutrition are Leucaena leucocephala, cassava leaf meal, Lablab purpureus, Tithonia diversifolia,Microdesmis puberula, Ipomoea asarifolia, Azadirachta indica, Tephrosia bracteolata among many others (Lopez et al., 1978; Lopez, 1986; Odunsi et al., 1996; Esonu et al., 2003; Odunsi, 2003; Ekenyem and Madubuike, 2006; Akande et al 2007). D’Mello (1995) recommended 5.0 and 10.0% dietary levels of leaf meals for broiler and laying hen respectively. Ademola and Farinu (2006) recommended dietary inclusions of Tithonia diversifolia in combination with either penicillin or streptomycin at 100 ppm in the diet of laying hens, while Odunsi (2003) recommended 100 and 150g/kg of Lablab purpureus leaf meal for laying hens.
However, D’Mello (1995) opined that major constraints of leaf meal utilization in non-ruminant animal nutrition are relatively high fibre, low energy, anti-nutritional factors and reduced feed intake.
Pawpaw (Carica papaya) is a plant native to Tropical America. It is known as “Okwuru bekee” in Igboland, “Gonda” in Hausa and “Ibepe” in Yoruba speaking areas of Nigeria. It is popular in the tropics and subtropics for its easy cultivation, rapid growth, quick economic returns, and adaptation to diverse soils and climates (Harkness, 1967; Campbell, 1984). Cultivated pawpaw is unbranched and usually dioecious plant, although hermaphroditic sex type occur (Harkness 1967; Seelig, 1970). However, pawpaw has been naturalized in many tropical and subtropical countries (Randall, 2002). Pawpaw tree is not considered to be a weed species (O.E.C.D., 2003). Pawpaw seedlings are among the most common seedlings to emerge from the forest floor. The fruit of papaw has a sweet taste and agreeable flavour and are high in vitamins (A, B, B2, C) and minerals (Ca, P, Fe), low in sodium, fat and contain practically no starch. Pawpaw leaf meal contains four identified proteolytic enzymes (Papain, Chymopapain A and B and Papaya Peptidase).
In the tropics, meat is often tenderized by wrapping in pawpaw leaves, the rate of reaction is slow at room temperature, increasing to maximum activity at 800C and rapidly inactivated at higher temperature. Hence, papain continues to tenderize the meat during the early stages of cooking (Health Watch, 2002).
There is scarcity of information in the literature on the effect of pawpaw leaf meal on finishing broilers. Thus, this study is designed to achieve the following objectives: