Performance characteristics and apparent nutrient digestibility of broiler finisher fed African yam bean cake as partial replacement for soybean meal

A three-week study was conducted to evaluate the performance characteristics and apparent nutrient digestibility of broilers finisher fed African Yam Bean Cake (AYBC). Treatment 1 had 0 % African yam bean cake and served as control while treatments 2, 3, 4 and 5 contained 5, 10, 15 and 20 % African yam bean cake respectively. One hundred and fifty-3-week old unsexed Marshal R broilers were carried over from starting phase and randomly allotted to the 5 dietary treatments in a completely randomized design (CRD). Each dietary group had 30 birds with 10 birds per replicate and replicated three times. Birds fed treatment 3 had the highest mean weight gain (1430 g) that was not significantly (p>0.05) different from others, treatment 1 gave the least feed conversion ratio (1.57) while least protein efficiency ratio (1.32) was obtained on birds fed treatment 3. Therefore, birds fed treatment 1 gave the best nutrient utilization. In conclusion, African yam bean cake enhanced performance characteristics and apparent nutrient digestibility of broiler finisher. Therefore, inclusion level of African yam bean cake beyond 20 % should be researched on.


INTRODUCTION
The two main protein sources for livestock feed are protein crops (e.g.legumes) and animal by-products.Large amounts of animal by-products come from industry (mainly meat and fish meal).The technologies for manufacturing these products are strict in order to avoid health crises (e.g.BSE).Even if their use is limited to certain animal species, in some regions (like the European Union) their use is currently legally forbidden.The safety assessment of animal protein for animal feed can also be performed directly at the farm level.
Legumes seeds are important sources of nutrients and can serve as high quality dietary protein sources to meet nutrient requirements (Perumal et al., 2001;Escudero et al., 2006).Legume seeds have an average of twice as much protein as cereals and the nutritive value of the proteins are usually high (Vijayakumari et al., 1997).The under-utilized legumes such as African yam bean seeds which have tremendous potential for commercial exploitation but remain ignored, offer a good scope in this context (Bhag Mal, 1992).
The African yam bean (Sphenostylis stenocarpa) is a climbing plant which twines and climbs to a height of over 3 m, requires staking, with each pod containing several edible seeds and is adapted to lowland tropical conditions (Wikipedia, 2005).It is one of the lesser known legumes (Ikhajiagbe et al., 2007b, Apata andOloghobo, 1990), widely cultivated in the southern parts of Nigeria for its edible seeds and tuberous roots (Ikhajiagbe et al., 2007a).The African yam bean is also cultivated in many other parts of Africa.The leaf and floral arrangements as well as the shape and color of seeds of this crop have been determined (Ikhajiagbe et al., 2007b andKlu et al., 2000).The leaves are stipulate with petioles 4-8 cm and rachis 1-3 cm.The African yam bean is partly cultivated in very poor soils often mixed plantings with yams, maize, okra and other vegetables (Ikhajiagbe et al., 2007a).The seed contains anti nutritional factors which reduce its nutritive values.
Anti-nutritional factors could penalize choosing some legume species.Many of the legumes in the tropics that are potentially valuable sources of protein contain anti-nutritional factors that can depress animal performance, such as trypsin inhibitors, oxalic acid, tannins and saponins.However, many of these can be inactivated to a greater or lesser extent by various processing methods, such as heat treatment, biological, chemical, urea fertilizer and mechanical.But mechanical processing is attracting interest in this finding because there is little information on African yam bean seeds.Therefore, this findings directed toward performance and apparent nutrient digestibility of broiler finisher fed African yam bean cake as partial replacement for soybean meal.

ExpErimEntal sitE
The experiment was carried out at the poultry unit,

sorting and procEssing of thE tEst ingrEdiEnt
The bean was sorted to remove stone, dirt and other spices apart from African yam bean seed (Brown variety).The bean was toasted for 35 minutes at a tempera-ture of 110 ˚C in a popcorn popper pot and subjected to extrusion by mechanical method using kernel extraction machine and formed African yam bean cake.

Table I. Percentage composition of broiler finisher
(Composición de la dieta de finalización).

ExpErimEntal diEts
Five diets were formulated to meet or exceed NRC recommendations (NRC, 1994).All diets were having percentage crude protein ranging between 17.58-16.67%.Maize was the major source of energy while soybean meal and African yam bean cake were sources of protein.Diet one was corn-soybean based (control) while African yam bean cake was added to diets 2, 3, 4, and 5 at the rate of 5, 10, 15, and 20 % inclusion rate respectively to replace soybean meal.The Microsoft excel package was used to formulate experimental diets.

ExpErimEntal birds and thEir managEmEnt
A total of 150 unsexed day-old marshal R strain broiler chicks were carried over from starting phase to finishing phase of five weeks.Thirty were randomly allotted to each of 5 dietary treatments and were repli-cated 3 times with 10 birds per replicate in a Completely Randomized Design (CRD).The birds were fed adlibitum with the experimental starter from day old for 5 weeks and placed on broiler finisher for 3 weeks.Litter were regularly turned and changed every 2 weeks to remove accumulating gasses from bird droppings.The feed given to the birds were weighed on daily basis with left over while cool, cleaned water was supplied unrestricted every day and the birds were weighed on weekly bases.

pErformancE data
Data collected daily on feed intake, records of body weight were taken weekly while record of mortality were kept throughout the period of the study.

fEEd intakE
Feed intake was determined by subtracting the weight of feed left over from the feed given.

body wEight gain
The birds were weighed on weekly basis and the weight was calculated by subtracting the weight in the preceding week from the current week.

fEEd convErsion ratio
This was calculated as the ratio of feed consumed to the weight gain.

Feed conversion ratio= ------protEin EfficiEncy ratio
Protein efficiency ratio was calculated as the ratio of weight gain to the protein intake.

Protein efficiency ratio= -------mEtabolic trial
At the end of seventh weeks, 3 birds per treatment with one bird from each replicate were picked randomly and housed in a metabolic cage.The birds were given 4 days to adapt to the new environment, a polythene bag was tied underneath.The feaces were collected from each bird for the remaining three days.Feed given to them were weighed and clean water was supply to the birds.The feaces collected from each bird were air dried for a week and crushed to granules then mixed and analyzed at the laboratory to know its nutritive values.

statistical analysis
All data were analyzed as a completely randomized design using one-way ANOVA (SPSS 2008).The differences were considered to be significant at p<0.05.

RESULT AND DISCUSSION
Table II show performance characteristics of broiler finisher.The feed intake for broiler finisher on test diets were higher than control diets.The level of feed intake was increased with increased level of African yam bean cake (AYBC).The higest values (2440.00g) was recorded on treatment 3 (10 %) while least (1644.00g) being in the control.This disagreed with (Adeniji, 2011) who reported decreased feed intake by broiler finisher as the blood vegetable waste meal increased in the diets.No significant differences (p>0.05) between final live weight, weight gain and feed intake of the experimental broiler finisher, means that nutrient to nutrient replacement level of soybean to African yam bean cake (AYBC) possessed a good protein content and possibly it has growth stimulating effect, as high level of protein is essential for body growth.This is in aggreement with the report of Adeniji (2012).Further more, improved feed conversion ratio of dietary inclusiion of AYBC shows that AYBC is a promising feedstuff and can reduce competition for soybean between monogastric animal, human being and industries, therefore, the need to use AYBC as alternative feedstuffs for monogastirc animals can not be overemphasised.Protein efficience ratio (PER) values were significantly (p<0.05)lower and similar for broiler on 5 % and 10 % inclusion of AYBC than control.This implies that AYBC was better utilized by broilers fed test diets.
Table III show nutrient digestibility of broiler finisher.The percentage dry matter, crude protein and ether extract values followed similar trends and were not significant (p>0.05)different accross dietary treatments.It means that the improved digestibility with higher level of AYBC implied that experimental broilers were able to effectively digest and utilised higher levels of

Feed intake Weight gain
Weight gain Protein intake AYBC which could have been excreted and decompose in the soil.Both crude fibre and ash were significantly (p<0.05)different.The crude fibre digestibilty values were significantly (p<0.05)higher in the test diets (AYBC) than control.This indicates that antinutritional factors (ANFs) levels in the test diets did not significantly impair the utilization of these nutrients which aggreed with reports obtained from literature (Aletor andOmolara, 1994 andAmaefule et al., 2004).
The lower values of the nutrient digestibility of control diet (0 % AYBC) clearly indicate that anti nutritional factors especially trypsin inhibitor in the soybean may have gotten a threshold were impairment of growth becomes apparent as a result of poor utilization.

CONCLUSION
The result of this study showed that African yam bean cake can be incorporated in diets of broiler finisher birds up to 20 % inclusion level without any deleterious effect on the performance characteristics and apparent nutrient digestibility of the birds.Therefore, inclusion level of African yam bean cake beyond 20 % should be researched on.

Table II .
Performance characteristics of broiler finisher fed African yam bean cake (Caracteristicas productivas de los broiler alimentados con torta de ñame africana).

Table III .
Apparent nutrient digestibility of broiler finisher fed African yam bean cake (Digestibilidad aparente de nutrientes en broiler acabados con torta de ñame africana).SEM Crude protein 38.86 a 40.42 a 39.31 a 39.97 a 39.95 a 0.32 Ether extract 53.63 a 52.02 a 52.60 a 52.23 a 52.97 a 0.27 Crude fibre 63.72 c 64.08 bc 63.76 c 64.68 ab 65.11 a 0.19 Ash 78.32 a 77.70 b 77.28 c 77.31 bc 77.53 bc 0.13 Dry matter 96.97 a 96.93 a 96.68 a 96.46 a 96.45 a 0.12 abcd Means on the same row with the same superscript are not significantly different (p>0.05).