The Use of Microbial Biotechnology in Value Addition to Cassava Wastes as Feed for Pigs: Prospects and Challenges

Abstract

Cassava peels were fermented through a combination of two lactic acid bacteria ( Lactobacillus coryneformis and Lactobacillus delbrueckii ) and a fungus ( Aspergillus fumigatus ) using solid substrate fermentation (SSF) technique for five consecutive days. The enhanced product designated as microbially fermented cassava peel (MFCP) was used at graded levels in the feed formulation for growing pigs. Four iso-nitrogenous and iso-caloric diets were formulated with MFCP at 0% (T1), 20% (T2), 40% (T3) and 60% (T4) inclusion levels. Twenty-four boarlings of an average initial weight of 37.15 kg were used in a fourteen-week trial to test the effect of these graded levels of MFCP on growth performance, digestive and reproductive physiology of the experimental animals. The result showed significant differences (P < 0.05) in mean daily feed consumption. Pigs in T3 had the highest feed intake (2.24 ± 0.05 kg), while pigs in T4 had the lowest (1.78 ± 0.04 kg). The final highest live weight was in T3 (72.00 kg) and the least in T4 (58.17 kg). The feed conversion ratios also showed significant differences (P < 0.05) among treatment means. The result obtained from gut morphometry showed that animals in T1 had the highest stomach weight (full and empty), while animals in T3 had the least rate of gastric emptying (81.50%). Animals in T3 and T4 had the longest small intestine (16.21 m and 15.35 m, respectively), while those in T4 had the longest colon (4.24 m). Animals in T1 and T2 had more numbers of gastric glands, while animals in T3 and T4 had more parietal cells. The reproductive indices revealed that animals in T1 were better in terms of the weight and relative weight of vesicular and Cowper’s gland, while animals in T4 had the highest value of the weight and relative weight of prostate gland. Proximate analyses of the ileal digesta revealed that the rate of nutrient absorption was highest in T3 and T1 and lowest in T4. Histological examination of the testes revealed normal testicular architecture in the control diet. The testes of animals fed 0%, 20% and 40% MFCP diets exhibited normal and intact lumen, Sertoli cells, and germ cells. However, animal fed 60% MFCP diet revealed massive disruption and degeneration of germinal epithelium, and complete erosion of the seminiferous tubules. It could be concluded that feeding pigs at 40% MFCP would enhance feed consumption, nutrient absorption and improve the growth rate of pigs. Using MFCP beyond 40% level on swine diet could compromise gut health through diarrhoeagenic disposition of the digesta in the distal colon and modification of the parietal and chief cells of the gastric glands. The hypertrophy of the prostate gland and vacuolization of the seminiferous tubules of pigs fed the 60% MFCP diet indicated a probable reduced reproductive performance.