Nutritive value of false yam seeds (Icacina oliviformis) as affected by sodium chloride treatment in layer chicken production

Abstract

Experiments were conducted to assess the nutritive value of false yam seed meal (FYSM) when subjected to sequential processing techniques (water treatment, sodium chloride and blanching). Matured false yam (Icacina oliviformis) fruits were harvested and seeds extracted. Two different FYSM samples were prepared. (1) An untreated sample was prepared by crushing fresh false yam seed and sun-dried to about 12% moisture. (2) A treated sample was crushed and soaked in water (1:2; w/v) for 12 days with water replaced every 3 days; after 12 days the sample was re-soaked in 1 M concentration of sodium chloride (NaCl) for 24 hours, washed, blanched and sun-dried to a moisture content of about 12%. The processed false yam seed samples were ground into gritty flour using a hammer mill (2 mm screen size). Maize served as the control. The false yam seed meals replaced maize (wt./wt. bases) in layer chick mash and layer grower diets, respectively. The nutrient compositions of the untreated and treated FYSM samples were determined. The proximate composition of the FYSM revealed that the untreated and treated samples contained high levels of dry matter (91.1 and 92.0%) and nitrogen free extractive (74.1 and 82.2%) respectively. However, the NaCl treated sample contained a relatively low level of crude protein (4.3%). Processing with NaCl significantly reduced the concentrations of essential amino acids compared to the untreated sample. The NaCl processing technique reduced the concentration of saponin and terpenes by 88 and 78% respectively. Feed preference test results indicated that layer chicks preferred NaCl treated diets 40 and 50% inclusion rate over those with lower inclusion rates; however, for the untreated FYSM they did not prefer inclusion rates of over 10%. In an apparent nutrient digestibility trial untreated and treated FYSM samples were each tested at inclusion levels of 30 and 50%. There were no significant (P > 0.05) differences in DM digestibility. Crude protein improved significantly (P ≤ 0.05) at 50% inclusion of NaCl treatment compared to 50% inclusion of untreated FYSM. Crude fiber and Nitrogen free extract digestibility were not significant (P > 0.05) in terms of treatment as well as levels of inclusion. Ash digestibility was significantly (P < 0.001) higher in diets containing untreated FYSM than in those containing NaCl treated. In a growth trial, feed intake improved (P ≤ 0.05) as the level of NaCl treated samples was increased up to 50%. Growth performance and feed conversion efficiency of pullets fed the control diet (maize) and diets containing NaCl treated FYSM were comparable (P > 0.05). It was concluded that false yam seed meal contains high dry matter and nitrogen free extract contents but is low in crude protein content. Mineral content was high with high contents of anti-nutrients (terpenes and saponins). However, the NaCl processing induced losses in crude protein, essential amino acids, and minerals as well as anti-nutrients. The method of processing used was effective in improving feed intake of pullets and did not have any adverse effect on their growth performance.