NUTRITIONAL IMPROVEMENT OF FALSE YAM (ICACINA OLIVIFORMIS) SEED MEAL FOR POULTRY

Abstract

Five separate experiments were conducted to assess the nutritive value of false yam seed meal (FYSM) when subjected to sequential processing techniques (water treatment, chemical treatment and blanching). Matured false yam(Icacina oliviformis) fruits were harvested and seeds extracted. Five different FYSM samples were prepared. One untreated sample (Un_T) was prepared by crushing fresh false yam seed and sun-dried to 12% moisture. Four treated samples (T), were crushed and each soaked in water (1:2; w/v) for 12 d with water replaced every 3 d. Afterwards, each sample was re-soaked in 1 M concentration of urea (Urea_T), sodium chloride (NaCl_T), sodium hydroxide (NaOH_T) or potassium hydroxide (KOH_T), for 24 h, washed, blanched and sun-dried to a moisture content of12%.Inexperiment1, the nutrient compositions of the untreated and treated FYSM samples were determined. The range of nutrient contents between untreated and mean of treated FYSM samples were DM(91.3 - 91.2%), CP (13.2 - 4.5%), EE (1.5 - 2.13%), NFE (71.4 - 79.9%), ash (2.5 - 2.1%), Ca (280 - 108 mg/kg), mg (52.8 - 15.1 mg/kg), K (110.6 272.6 mg/kg), Na (557.7 - 618.2 mg/kg) and P (0.31 - 1.44 mg/kg). Processing of the 4 FYSM samples drastically reduced the concentrations of essential amino acids compared to the untreated samples: Lys. (0.35 - 0.11%), Met. (0.1 - 0.03%), Leu. (0.9 - 0.27%), Ala. (0.6 - 0.18%), Tryp. (0.16 - 0.06%), Val. (0.5 - 0.17%), Threo. (0.42 - 0.12%), Arg. (1.43 - 0.27%), His. (0.36 - 0.14%) and Phenylala. (0.58 - 0.17) respectively. The concentrations of terpenes were reduced by processing;Urea_T(91.9%),NaCl_T(88.3%),NaOH_T(84.1%)and KOH_T(81.6%). Similarly, the concentrations of saponins were reduced by processing; Urea_T (68.0%), NaCl_T (76.8%), NaOH_T (69.6%) and KOH_T (68.0%). Experiment 2 evaluated feed preference and apparent nutrient digestibility of a maize-based diets containing treated false yam seed meals (TFYSM) at 0, 5, 10, 15, 20, 25, 30, 35, 40, 45 and 50%. Feed preference tests were conducted with 21 day-old broiler chicks (Cobb 500) using a RCBD. Apparent nutrient digestibility trial was conducted with broiler chicks in 5x6 factorial design for 15 days using the total collection method. The preference data indicated that feed intake was not compromised when maize was substituted by NaCl_T, NaOH_T, and KOH_T FYSM at all levels, while Urea_T FYSM was tolerated up to 30% and the Un_T FYSM at 5% dietary level. Dry matter digestibility was generally high (> 75%) in all diets except for Un_T (68%). Control diet (74.32%) and NaOH_T diets had similar CP digestibility (74.7%), but was higher (P<0.05) than KOH_T diets (69.2%), while Un_T diets had reduced CP digestibility (58%). Digestibility of NFE ranged from 77.4% (Un_T) to 93.8% (KOH_T). Experiment 3 evaluated apparent metabolizable energy(AME)and nutrient metabol is ability(NM) of the maize-based diets containing TFYSM using the same experimental design in experiment 2. AME of the diets indicated increasing trend as TFYSM was increased in the diets. Diets containing TFYSM improved (P<0.001) DM, CP and carbohydrate metabolisability. There was interaction (P<0.017) between method of processing and level of inclusion on gross energy metabolisability. Experiment 4 examined the effect of NaOH_TFYSM on the growth performance and blood profile of female broiler chickens (Cobb 500). Four dietary treatments containing NaOH_T FYSM at 0, 100,300and500 g/kg in broiler finisher diets were tested using a Completely Randomized Design and each treatment had quadruplicate lots (8 birds/replicate). Feed and water were provided ad libitum from 21-56 d of age. Data collected were analysed using GenStat. Growth performance variables of all treatment groups were similar (P>0.05). Birds fed diets containing 0, 100 and 300g/kg NaOH_T FYSM had similar (P>0.05) (78.5-79.5%) carcass dressing, but higher (P<0.003) than those fed diets at 500g/kg. All haematological variables were similar (P>0.05) except RBC in birds fed NaOH_T FYSM diet. Liver function test indicated significant (P<0.048) improvement in only albumin values when NaOH_T FYSM was included beyond 100g/kg. However, all renal function variables increased (P<0.05) with the inclusion of NaOH_T FYSM in the diets. Economics of feeding NaOH_T FYSM revealed a significant (P<0.05) reduction in total feed cost per bird and feed cost per kg gain. Meat quality of the broilers was evaluated and the results indicated that NaOH_TFYSMinclusionupto500g/kg improved(P<0.001)protein content of the meat. Furthermore, carcass dress weight, primal cuts and sensory characteristics were not affected (P>0.05). Lipid oxidation in the meat differed (P<0.001) significantly among the treatment groups but were much lower than the maximum permissible level of 25 meq/kg meat. In experiment 5, the effect of varying levels (0, 100, 300 and 500 g/kg) of KOH_T FYSM on growth and blood profile of male broiler chickens was evaluated as in experiment 4. Growth performance variables as well as percent carcass dressing of all treatment groups were similar (P>0.05). Relative heart weight increased (P<0.05) whereas liver and spleen weights decreased (P<0.05). Among the haematological variables evaluated, Hb, MCV, MCH and MCHC values reduced (P<0.05) significantly with increasing inclusion levels of KOH_T FYSM in the diets. Liver function variables remained unchanged except for serum albumin which differed (P<0.05) between the control birds and their counterparts. All renal function variables were similar (P>0.05). Economic variables were similar (P<0.05) for all diets. Similar meat quality evaluation procedures as in experiment 4 was undertaken in experiment 5. The results indicated that KOH_T FYSM inclusion up to 500g/kg did not affect(P>0.05)carcass characteristics of the birds.Relative weight of breast muscle decreased (P<0.05) at inclusion level of 100 g/kg and subsequently improved at 300 and 500 g/kg. Sensory attributes of the meat were similar (P>0.05) among the treatment groups. The inclusion of KOH_T FYSM improved (P<0.001) protein content of the meat. Lipid oxidation in the meat differed (P<0.001) significantly among the treatment groups but were much lower than the maximum permissible level of 25meq/kg meat. It can be concluded that sequential use of water-based and chemical treatment methods using NaOH or KOH offers the potential to use FYSM as an alternative feed stuff in broiler chicken diets.