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.
Globally, livestock production is growing more dynamically than any other agricultural sector. As countries become more affluent, demand for livestock-derived food has substantially increased, leading to a major transformation of animal food production. Pig and poultry production are the fastest growing and industrialized livestock subsectors with annual production growth rates of 2.6% and 3.7% respectively over the past decade [
The potential use of cassava peel to adequately fill this nutritional gap is heavily constrained by intrinsic factors like their high crude fibre level, low nitrogen content and the presence of anti-nutrients [
Fresh cassava peels were collected from cassava processing mills within Akure town, Ondo State, Nigeria. The peels were processed by the methods described by Aro [
Data were collected for weekly weight change, daily feed intake and feed conversion ratio throughout the 14 weeks of the trial. At the end of the experiment, all the animals were mechanically stunned and slaughtered. Immediately after death, the abdominal cavity was opened and the entire gastrointestinal tract was immediately removed. Different sections of the gastro-intestinal tract were ligated and cut into the following segments: sto-
Ingredients | T1 | T2 | T3 | T4 |
---|---|---|---|---|
Maize | 40.00 | 35.00 | 15.00 | 0.00 |
Rice bran | 11.00 | 7.20 | 10.00 | 0.00 |
Palm kernel cake | 26.30 | 16.50 | 14.50 | 21.30 |
Groundnut cake | 17.00 | 18.30 | 17.50 | 15.70 |
MFCP | --------- | 20.00 | 40.00 | 60.00 |
Vegetable oil | 2.50 | ---------- | -------- | -------- |
Bone meal | 1.50 | 1.50 | 1.50 | 1.50 |
Oyster shell | 0.50 | 0.50 | 0.50 | 0.50 |
Premix | 0.50 | 0.50 | 0.50 | 0.50 |
Salt | 0.50 | 0.50 | 0.50 | 0.50 |
Total | 100.00 | 100.00 | 100.00 | 100.00 |
Crude protein (%) | 18.07 | 18.09 | 18.09 | 18.04 |
Crude fibre (%) | 6.20 | 11.35 | 17.87 | 24.01 |
M. E. (Kcal/kg) | 3022.82 | 3012.30 | 3003.15 | 3015.74 |
HCN Conc. (mg/kg) | 0.00 | 5.88 | 11.16 | 16.75 |
MFCP = Microbially fermented cassava peel; HCN = Hydrogen cyanide; M. E. = Metabolizable energy; T1 = Control diet; T2 = Diet with 20% inclusion of MFCP; T3 = Diet with 40% inclusion of MFCP; T4 = Diet with 60% inclusion of MFCP.
mach, small intestine, large intestine and caecum for measurement. The length of small and large intestine were determined using a linear measuring tape. The weights of caecum and stomach (full and empty) were also determined.
Tissue samples from the stomach and testis were collected for histological examination. Sections were then observed with a light microscope and photographs were taken at 600× magnification. Also, gonadal parameters like the weight of the accessory glands and testicular histology were determined as response criteria to the treatment diets.
Data generated were subjected to analysis of variance (ANOVA) using SPSS version 16 statistical package. Mean separation was done with Duncan’s multiple range test of the same statistical package.
The result of the performance of grower pigs fed varying levels of MFCP is shown in
Parameters | T1 | T2 | T3 | T4 |
---|---|---|---|---|
Average feed intake (kg/d) | 1.84 ± 0.56b | 1.94 ± 0.18b | 2.24 ± 0.05a | 1.78 ± 0.04b |
Initial live weight (kg) | 37.00 ± 4.49 | 37.67 ± 3.23 | 37.50 ± 2.03 | 37.17 ± 2.17 |
Final live weight (kg) | 70.50 ± 9.27 | 64.00 ± 7.21 | 72.00 ± 3.76 | 58.00 ± 0.89 |
Total weight gain (kg) | 33.50 ± 5.47 | 26.33 ± 4.26 | 34.50 ± 5.22 | 20.83 ± 2.14 |
Daily weight gain (kg) | 0.34 ± 0.06 | 0.27 ± 0.04 | 0.35 ± 0.06 | 0.21 ± 0.02 |
FCR | 5.41 ± 1.40b | 7.19 ± 1.62b | 6.40 ± 1.75b | 8.48 ± 0.80a |
Feed efficiency | 0.19 ± 0.03a | 0.14 ± 0.04a | 0.16 ± 0.02a | 0.12 ± 0.01b |
HCN intake/kg body weight (mg/kg) | 0.00 ± 0.00d | 0.18 ± 0.24c | 0.35 ± 0.16b | 0.51 ± 0.07a |
Mean ± Standard Deviation. a, b, c, d = Means with different superscripts within the same rows and for the same parameters are significantly different (P < 0.05); MFCP = Microbially fermented cassava peel; T1 = 0% MFCP inclusion as control diet; T2 = 20% MFCP inclusion of the diet; T3 = 40% MFCP inclusion of the diet; T4 = 60% MFCP inclusion of the diet; FCR = Feed conversion rate; HCN = Hydrogen cyanide.
recorded for animals on T4 could have resulted in poor growth of the animals. Hence HCN/kg body weight in MFCP for growers pig should not 0.35 mg/kg for better growth performance.
The morphometric data (
The weight of stomach content (ingesta) was highest in T3 than in all other treatments. This probably depicts that animals on T3 retained dietary nutrients in the stomach for digestion/processing longer than animals on T1, T2, and T4. This could also mean that dietary nutrients were retained longer and made more accessible to enzymatic digestion and hence responsible for the presence of more number of parietal cells (
Histological examination of the fundic region of the stomach (
In animals fed T4, there were alterations in shape and structure of gastric glands with parietal cells unevenly distributed in the glands. The chief cells were not fully formed. The toxigenic nature of residual cyanide at 60% inclusion may have caused the malformation of chief cells and gastric glands observed in stomach of animals fed T4. Hence most of the nutrients in the diet (T4) must have escaped the stomach without much action of hydrochloric acid secretion for digestion.
The rate of gastric emptying and proximate composition of the ileal content (
Parameters Weight of Stomach | T1 | T2 | T3 | T4 |
---|---|---|---|---|
Full (kg) | 1.42 ± 0.61 | 0.92 ± 0.14 | 1.20 ± 0.15 | 0.88 ± 0.17 |
Empty (kg) | 0.87 ± 0.37a | 0.43 ± 0.33b | 0.36 ± 0.18b | 0.48 ± 0.06b |
Weight of stomach content (kg) | 0.55 ± 0.16b | 0.49 ± 0.13b | 0.84 ± 0.22a | 0.40 ± 0.13b |
Weight of empty Caecum (kg) | 0.67 ± 0.07ab | 0.62 ± 0.04b | 0.83 ± 0.17a | 0.51 ± 0.02c |
Length of small intestine (m) | 15.28 ± 0.75 | 14.59 ± 1.11 | 16.21 ± 0.86 | 15.35 ± 0.43 |
Length of large intestine (m) | 4.11 ± 0.56 | 4.53 ± 0.25 | 4.22 ± 0.15 | 4.24 ± 0.17 |
Mean ± Standard Error. a, b, c, ab = Means with different superscripts within the same rows and for the same parameters are significantly different (P < 0.05); MFCP = Microbially fermented cassava peel; T1 = Control diet; T2 = Diet with 20% inclusion of MFCP; T3 = Diet with 40% inclusion of MFCP; T4 = Diet with 60% inclusion of MFCP.
The ileal content of T4 had the lowest dry matter (DM) value (16.36 g/100 g) while T3 had the highest value (19.42 g/100 g). Conversely, T4 had the highest moisture content. The high moisture content in T4 may be as a result of the water binding ability of dietary fibre [
Parameters | T1 | T2 | T3 | T4 |
---|---|---|---|---|
DM | 19.05 ± 0.42ab | 17.95 ± 0.30b | 19.42 ± 0.42a | 16.36 ± 0.30c |
Moisture | 80.95 ± 0.42ab | 82.05 ± 0.30b | 80.58 ± 0.42c | 83.64 ± 0.30a |
Crude fibre | 11.20 ± 0.09c | 13.18 ± 0.30b | 11.37 ± 0.04c | 15.64 ± 0.34a |
CP | 15.60 ± 0.19b | 18.10 ± 0.35ab | 13.74 ± 0.39c | 18.33 ± 0.22a |
EE | 9.51 ± 0.07c | 9.76 ± 0.06b | 9.70 ± 0.04bc | 10.31 ± 0.07a |
Ash | 11.07 ± 0.41b | 9.25 ± 0.13c | 10.62 ± 0.10b | 12.14 ± 0.34a |
NFE | 52.63 ± 0.22b | 49.69 ± 0.20c | 54.57 ± 0.35a | 43.57 ± 0.62d |
RGE | 81.02 ± 8.51b | 83.87 ± 4.35b | 81.50 ± 6.99b | 88.89 ± 3.67a |
a, b, c, d, ab = Means on the same rows but with different superscripts are statistically (P < 0.05) significant; DM = Dry matter; CF = Crude fibre; CP = Crude protein; EE = Ether extract; NFE = Nitrogen free extract. T1 = No inclusion of MFCP (Control); T2 = 20% inclusion of MFCP; T3 = 40% inclusion of MFCP; T4 = 60% inclusion of MFCP; RGE = Rate of gastric emptying.
and this could be as a result of the high crude fibre content of this diet. This is in consonance with the report of Bindelle [
The low fat content of T1 is an indication that fat was well absorbed in T1, while high fat content in T4 is an indication of poor absorption and this may be as a result of the fact that dietary fibre hinders the absorption of all other nutrients [
Pigs that were fed T1 had the heaviest vesicular glands when compared with pigs fed MFCP diets. The toxigenic effect of the residual cyanide of the cassava peel could have been responsible for the low weight of the vesicular glands in the MFCP-fed pigs. The heavier vesicular glands in pigs that were fed T1 is an indication of greater fluid volume of semen to ensure optimum motility and fertility [
Parameters | T1 | T2 | T3 | T4 |
---|---|---|---|---|
DM | 38.75 ± 0.42a | 33.37 ± 0.30b | 37.78 ± 0.39a | 29.36 ± 0.41c |
Moisture | 61.25 ± 0.42c | 66.63 ± 0.30b | 62.22 ± 0.39c | 70.64 ± 0.41a |
CF | 8.18 ± 0.08c | 9.47 ± 0.09b | 8.45 ± 0.06c | 12.92 ± 0.26a |
CP | 15.18 ± 0.21b | 16.85 ± 0.33a | 15.07 ± 0.27b | 16.97 ± 0.43a |
EE | 8.76 ± 0.07bc | 8.93 ± 0.08b | 8.31 ± 0.07c | 10.11 ± 0.29a |
Ash | 11.06 ± 0.37bc | 10.28 ± 0.15c | 11.46 ± 0.22ab | 12.28 ± 0.38a |
NFE | 56.82 ± 0.55a | 54.48 ± 0.26b | 56.71 ± 0.58a | 47.73 ± 0.40c |
a, b, c, ab, bc = Means on the same rows but with different superscripts are statistically (P < 0.05) significant; DM = Dry matter; CF = Crude fibre; CP = Crude protein; EE = Ether extract; NFE = Nitrogen free extract; T1 = 0% inclusion of MFCP (Control); T2 = 20% inclusion of MFCP; T3 = 40% inclusion of MFCP; T4 = 60% inclusion of MFCP.
Parameters | T1 | T2 | T3 | T4 |
---|---|---|---|---|
Vesicular gland | 0.35 ± 0.03a | 0.15 ± 0.03d | 0.30 ± 0.11b | 0.23 ± 0.04c |
Prostate gland | 0.10 ± 0.00b | 0.15 ± 0.03a | 0.08 ± 0.01c | 0.15 ± 0.06a |
Cowper’s gland | 0.20 ± 0.00a | 0.13 ± 0.01b | 0.13 ± 0.01b | 0.13 ± 0.01b |
a, b, c, d = Means on the same rows but with different superscripts are statistically (P < 0.05) significant; T1 = 0% inclusion of MFCP (control); T2 = 20% inclusion of MFCP; T3 = 40% inclusion of MFCP; T4 = 60% inclusion of MFCP.
Parameters | T1 | T2 | T3 | T4 |
---|---|---|---|---|
Vesicular gland | 0.53 ± 0.05a | 0.23 ± 0.02c | 0.44 ± 0.17b | 0.41 ± 0.09b |
Prostate gland | 0.15 ± 0.01b | 0.25 ± 0.07a | 0.11 ± 0.02c | 0.28 ± 0.11a |
Cowper’s gland | 0.30 ± 0.02a | 0.20 ± 0.01b | 0.19 ± 0.03b | 0.23 ± 0.03b |
a, b, c = means on the same rows but with different superscripts are statistically (P < 0.05) significant; T1 = 0% inclusion of MFCP (control); T2 = 20% inclusion of MFCP; T3 = 40% inclusion of MFCP; T4 = 60% inclusion of MFCP.
these two glands in pigs fed MFCP in comparison with those in the control would therefore mean less secretion and hence reduced ovum fertilizing capacity of the seminal plasma of pigs fed MFCP-based diets. The relatively lower weights of the vesicular and Cowper’s glands would have been caused by the adverse effect of residual cyanide in the peels [
The histopathology of the testes of animals on T1 (control diet) in
served compared with testis of animals on T1. In T3 (
In T4 (
These Histological examinations revealed progressive changes in testicular architecture according to treatment effects (Figures 2-5). This disruption and degeneration of the testicular tissues could be attributed to the toxic effect of residual cyanide (16.75 mg/kg) on the testes at 60% level of inclusion. This was similar to the alteration observed in spermatogenesis due to inclusion of gossypol [
The sloughing of apical seminiferous tubule epithelium into the lumen observed in the testis of animals fed T4 (
Vacuolization and keratinization of seminiferous tubule and peritubular tissue of the seminiferous tubules were increased in the testes of animal fed MFCP diets. The vacuolization of the seminiferous tubule may be as a result of toxigenic nature of residual cyanide in MFCP that could probably engender reduced fertility. This is similar to the vacuolization and degeneration of seminiferous tubule observed in rat due to obstruction or dysfunction of epididymis [
The interstitial cells of Leydig were prominently interspersed in testes of animals fed diet T1 (
The performance of the grower pigs was better in terms of total weight gained of the pigs in favour of the 40% level of inclusion of MFCP. This means that the inclusion of MFCP at 40% level in the diets of grower pigs will not adversely affect growth performance and the digestive physiology of the pigs. The result however reveals that nutrient and water absorption in the GIT are affected by dietary inclusion of microbially fermented cassava peel. These performance indicators of the normal gastro-intestinal physiology were decreased at 60% inclusion level of MFCP. Feeding pigs with inclusion of MFCP above 40% could therefore adversely affect the rate of nutrient absorption, gut health and general health status of growing pigs. Therefore, within the limit of this study MFCP should not be fed above 40% to growing pigs. Also, feeding boars with more than 40% inclusion MFCP could depress reproductive performance. The high relative weight of the prostate glands in pigs fed on the MFCP diets calls for more empirical evaluation, as it is suggestive of a pathological condition in the similitude of an abnormal enlargement of the gland in response to the diets. Hence, predisposition to prostate cancer could result from prolonged exposure to diets containing more than 40% MFCP as observed in this study. The testicular architecture observed in this study showed that feeding microbially fermented cassava peel higher than 40% inclusion in diet would lead to reduction in reproductive performance of growing pigs.
The prospects of value addition to cassava peels through the intervention of micro-organisms within the limit of this experiment are in the areas of better growth performance and feed conversion up to 40% inclusion level. The challenges or constraints are lowered reproductive performance and reduced growth rate that are experienced at levels of inclusion higher than 40%, probably due to the crude fibre and residual cyanide levels in the microbially fermented peels. The focus of further research in this field should therefore be directed at those micro-organisms with better crude fibre and cyanide degrading ability than the ones used in this trial. However, from this experiment, tolerant levels of 0.35 mg of HCN intake/kg body weight, 11.16 mg of HCN/kg of feed and crude fibre level of 17.87% were established for growing pigs fed dietary inclusion of cassava peels fermented with a consortium of Lactobacillus coryneformis, Lactobacillus delbrueckii and Aspergillus fumigatus.
The authors express their gratitude to the Federal University of Technology, Akure under the Centre of Excellence for Food Security, for providing financial support for this research work.