LOW NUTRITIONAL QUALITY OF UNCONVENTIONAL TROPICAL CROP SEEDS IN RATS

As the search for alternative sources of food to alleviate hunger cont inues, this study was undertaken to determine the biological value in growing rats (BV) of proteins of some lesser known tropical seeds gath ered in Nigeria. Antinutritional factors (trypsin inhibitors, phytic a cid, oxalate, tannin, alkaloids) and amino acid compositions were also determined, and protein digestibility-corrected amino acid score (PDC AAS) was calculated using the amino acid requirement pattern of the pr eschool child and individual seed-specific correction factors for crud e protein. A rat growth and balance study was conducted to determine d igestibility, nitrogen-, and energy balance by feeding as the only uns upplemented protein source milled and heat-treated seeds of Adansonia digitata (Bombacaceae) and Prosopis africana, Lonchocarpus sericeus, E nterolobium cyclocarpium, Sesbania pachycarpa and Pterocarpus osun (Le guminosae) in comparison to casein fortified with methionine (control) . Diets containing P. africana and L. sericeus seeds caused poor feed intake and weight loss in rats and were excluded from the nitrogen-bal ance test. Among the seed samples, S. pachycarpa followed by A. digita ta showed the most advantageous nutritional quality [amino acid compos ition, digestibility, BV and net protein utilization (NPU)]. True dige stibility was 82.9 and 74.5 vs. 98.5, BV was 64.6 and 70.0 vs. 90.4, a nd NPU was 53.5 and 52.1 vs. 89.0 for S. pachycarpa and A. digitata vs , casein (control), respectively. In terms of PDCAAS, lysine was the f irst limiting amino acid for S. pachycarpa (88%) and for A. digitata ( 58%). The PDCAAS of all essential amino acids was below 100% for E. cy clocarpium (e.g., cysteine + methionine: 37%) and for P. africana (e.g ., threonine: 46%, except valine and a very high content of cycteine a nd methionine). In conclusion, all seeds tested in the rat balance tri al were of inferior quality compared to casein. Before these tropical seeds could be used as food components or feed supplements, safety stu dies and proper processing to remove antinutritional factors and possi ble toxic constituents were required.