In Cameroon, there is a deficit of about 8 kg/inhabitant/year of protein of animal origin in the population . To feed and satisfy these needs, caviar farming can be an alternative. Indeed, caviar farming is an important element in the rural landscape in Cameroon, in that it improves the rather meagre income of farmers . However, one of the main handicaps to the development of livestock farming in this area is its diet. Indeed, the animals feed mainly on kitchen waste, crop residues and forage grasses, which are often deficient in essential nutrients such as proteins and minerals . The result is low productivity.
Improving the productivity of Guinea pigs can be achieved, among other things, by improving their diet and, above all, by providing them with a balanced food ration . Thus, one easily achievable solution is the use of fodder legumes and other non-conventional protein sources with an established nutritional value as a poor food supplement . Among these unconventional protein sources are the seeds and leaves of Moringa oliefera. Moringa oleifera belongs to the mono-generic family Moringaceae . It is a tree native to north-western India from Pakistan, which borders the Himalayas . It has been introduced into all tropical and subtropical regions  and has become naturalized in many African countries . A tree can produce an average of 15,000 to 25,000 seeds per year . The leaves of this plant, in Cameroon as in most of the countries where it is produced, are used for food and feed. Notably the study by  showed that the leaves of Moringa oleifera improved growth and carcass yield in Guinea pigs. As for the seeds of Moringa oleifera, they are used to treat and purify milk, honey and water  , thanks to its richness in active cationic polyelectrolytes. In North Cameroon, the seeds are also pressed to extract the oil, and the resulting residues in the form of cake are used for fattening (cattle and small ruminants).
One of the major problems limiting the use of Moringa oleifera seeds in animal feed is their high concentration of anti-nutritional factors that reduce the ability of microorganisms to digest the nutrients they contain . Consequently, detoxification methods (physical and chemical), more or less expensive, have been developed to control the negative effects of these anti-nutritional factors to a threshold that is harmless for both humans and animals . Thus, the work of  showed that pulping reduced the levels of condensed tannins, flavonoids and phytates contained in M. oleifera seeds. According to , soaking helps neutralize the enzyme inhibitors present in the seeds in order to improve the digestion of certain complex molecules. In Cameroon, very little work has been done so far on the use of M. oleifera seeds subjected to different treatments on the ingestion and digestibility of rations in Guinea pigs. It is therefore to fill this gap that the present work was initiated with the main objective of determining the effect of M. oleifera seeds treated and included in a concentrated granulated feed associated with Pennisetum purpureum on ingestion and digestibility in Guinea pigs.
2. Materials and Methods
2.1. Study Area
This study was conducted during the month of April 2018, in the Animal Production and Nutrition Research Unit (URPRONAN) of the Faculty of Agronomy and Agricultural Sciences (FASA) of the University of Dschang. The city of Dschang is located at the 15th degree of the East meridian, at latitude 5˚36' - 5˚44' North and longitude 09˚85' - 10˚06' East. The climate of the region is equatorial of Cameroonian type modified by altitude. Rainfall in the locality varies between 1500 and 2000 mm per year. The average annual temperature is around 20˚C, total annual insolation at 1800 hours and average relative humidity varies between 40% and 90%.
2.2. Plant Material
The plant material consisted of seeds of Moringa oleifera (whole, soaked and shelled) and Pennisetum purpureum. Pennisetum purpureum was mowed before flowering at the Dschang University Farm. As for the seeds of Moringa oleifera, they were bought in North Cameroon.
2.3. Animal Material and Housing
Forty English Guinea pigs (20 males and 20 females) aged approximately 4 to 5 months and with an average weight of 350 ± 50 g were used for the evaluation of ingestion and digestibility. The animals were placed in individual wire cages of 10.6 dm3 (76 cm × 46.5 cm × 30 cm) each equipped with a 100 g plastic feeder and a plastic drinker.
2.4. Evaluation of the Chemical Composition of Moringa oleifera Seeds and Preparation of Rations
The chemical composition of Moringa oleifera seeds was carried out to determine the contents of dry matter, ash, organic matter, crude cellulose, crude protein, fat, condensed tannins, non-nitrogenous extractives and total phenols according to the methods described by . The chemical composition of Moringa oleifera seeds was determined at the Laboratory of Animal Nutrition of the University of Agricultural Sciences and Veterinary Medicine of Cluj-napoca (Romania).
Four types of concentrates (Table 1) were manufactured, where three containers 7% of Moringa oleifera seeds, constituted according to the different treatments applied to the seeds.
Each concentrate was then granulated and combined with Pennisetum purpureum to make up the various rations as follows:
- TEM + Pp: concentrate without Moringa seed + 105 g of P. purpureum/Animal/Day;
- MO-whole + Pp: concentrate containing whole Moringa seed + 105 g of P. purpureum/Animal/Day;
Table 1. Centesimal composition of granulated concentrates.
TEM: control concentrate without Moringa oleifera seeds; MO-whole: concentrate containing whole Moringa oleifera seeds; MO-water: concentrate containing Moringa oleifera seeds soaked for 24 hours and MO-peeled: concentrate containing peeled Moringa oleifera seeds.
- MO-water + Pp: concentrate containing peeled Moringa seeds + 105 g of P. purpureum/Animal/Day;
- MO-peeled + Pp: concentrate containing Moringa seeds soaked for 24 h + 105 g of P. purpureum/Animal/Day.
2.5. Evaluation of Ingestion and In Vivo Digestibility of Rations
For each of the treatments, 5 males and 5 females were used. These animals were randomly assigned to individual cages, and feed was served only once each day between 8 and 9 hours. For intake assessment, the amounts of feed served were recorded, and refusals were collected daily and weighed before any further distribution. Refusals were quantified to determine the amounts of food ingested. Food ingestion or consumption was calculated according to the formula opposite:
Food ingestion = Daily amount of food served − Amount not consumed (refusal)
The digestibility trial was preceded by a period of adaptation of the animals to the digestibility cage and the pelleted compound feed, which lasted 10 days. During this period, the amounts of granulated concentrate associated with the Pennisetum purpureum served were adjusted to the animal’s consumption. During the data collection period which lasted 7 days, each morning before the feed was distributed, the faces were collected, weighed and dried at 60˚C in the laboratory in a ventilated oven. Subsequently, the analysis of their dry matter (DM), organic matter (OM), crude protein (CP) and crude fiber (CF) content was done according to the method described by . The apparent digestive utilization coefficients of Dry Matter (CUDaDM), Organic Matter (CUDaOM), Crude Protein (CUDaCP), and Crude fiber (CUDaCF) were calculated according to the formula of :
CUDaDM (%) = (DM ingested − fecal DM)/(DM ingested) × 100
CUDaMO (%) = (OM ingested − OM fecal)/(OM ingested) × 100
CUDaPB (%) = (CP ingested − CP fecal)/(CP ingested) × 100
CUDaCB (%) = (CF ingested − CF fecal)/(CF ingested) × 100
2.6. Statistical Analysis
Food intake and nutrient digestibility data were subjected to analysis of variance (ANOVA) at a factor following the general linear model (GLM). When significant differences existed between treatments, the separation of the means was done by the Waller Duncan test at the 5% significance level . SPSS 21.0 analysis software was used.
3.1. Effect of Different Treatments on the Chemical Composition of M. oleifera Seeds
The different treatments carried out on M. oleifera seeds have had a variable influence on its chemical composition (Table 2). The DM content of peeled M. oleifera seeds was significantly (p < 0.05) higher than the DM content of whole M. oleifera seeds and that of seeds soaked for 24 hours.
The organic matter, protein and fat contents of whole M. oleifera seeds and M. oleifera seeds soaked for 24 hours were comparable (p > 0.05) and significantly (p < 0.05) lower than those of dehulled M. oleifera seeds. The content of non-nitrogenous extractives was significantly (p < 0.05) lower in M. oleifera hulled seeds. Condensed tannins and total phenols were significantly (p < 0.05) lower in M. oleifera seeds soaked for 24 hours. On the other hand, the different treatments carried out on M. oleifera seeds did not significantly (p > 0.05) affect the crude cellulose content.
3.2. Ingestion of Granulated Concentrate with Inclusion of M. oleifera Seeds Subjected to Different Treatments Associated with P. purpureum in Guinea Pigs
Ingestion of granulated concentrates with different treatments of Moringa oleifera seeds induced no significant effect (p > 0.05) on the ingestion of P. purpureum in Guinea pigs (Table 3). However, different treatments of Moringa oleifera seeds significantly (p < 0.05) influenced the ingestion of granulated concentrate in Guinea pigs. Indeed, the intake of granulated concentrate in the MO-whole + Pp, MO-water + Pp and MO-peeled + Pp rations was comparable (p > 0.05) on the one hand and significantly (p < 0.05) lower than the intake of the TEM + Pp ration.
The different treatments of M. oleifera seeds did not significantly influence (p > 0.05) the total ingestion of dry matter and organic matter in the Guinea pigs whatever the ration.
The crude cellulose intake of the MO-water + Pp ration was comparable (p > 0.05) to the TEM + Pp ration and significantly (p < 0.05) higher than the BC
Table 2. Chemical composition of M. oleifera seeds subjected to different treatments.
a,b,c: Averages with the same letters on the same line are not significantly different at the 5% threshold; MS: Dry Matter; SEM: Standard Error on the Mean; p: Probability.
Table 3. Ingestion of granulated concentrate with inclusion of M. oleifera seeds subjected to different treatments associated with P. purpureum in Guinea pigs.
a,b,c: Averages with the same letters on the same line are not significantly different at p < 0.05.
intake of the MO-whole + Pp and MO-peeled + Pp rations. Moreover, the crude fiber intake data obtained with the TEM + Pp ration did not show a significant difference (p > 0.05) with those obtained with the MO-peeled + Pp ration. The lowest significantly (p < 0.05) value of crude fiber intake was obtained with the MO-whole + Pp ration.
Crude protein intake of the TEM + Pp and MO-whole- + Pp rations were comparable (p > 0.05) on the one hand, and significantly (p < 0.05) higher than the intake of crude protein of the MO-whole- + Pp and MO-water + Pp rations on the other hand. The crude protein intake of the MO-whole + Pp ration was significantly (p < 0.05) lower than that of the other rations.
3.3. Nutrient Digestibility of the Granulated Concentrate with Inclusion of Seeds of M. oleifera Subjected to Different Treatments Associated with P. purpureum in Guinea Pigs
In this trial, the digestive utilization factor of DM, OM and CF of rations containing differently treated M. oleifera seeds was comparable (p > 0.05) to the control ration (Table 4). Similarly, the crude protein digestibility of the MO-whole + Pp rations was comparable (p > 0.05) to that of the MO-water + Pp ration. On the other hand, the CP digestibilities of the TEM + Pp and peeled + Pp rations were comparable and significantly higher than those of the MO-whole + Pp ration.
The fat and protein contents of whole M. oleifera seeds and 24-hour soaked seeds were comparable and significantly lower than those of dehulled seeds. This could be attributed to seed pulping. Indeed, these elements are concentrated in large quantities in the kernels compared to the shell. Soaking and pulping significantly decreased the levels of condensed tannins and total phenols in M. oleifera seeds, but this decrease was more pronounced in M. oleifera seeds soaked for 24 hours. This result is consistent with work by  which showed that pulping reduced the levels of condensed tannins, flavonoids and phytates in
Table 4. Digestibility of granulated concentrate with inclusion of M. oleifera seeds subjected to different treatments associated with P. purpureum in Guinea pigs.
a,b,c: Averages with the same letters on the same line are not significantly different at p < 0.05; CUDa: apparent digestive utilization factor.
M. oleifera seeds. In addition,  reported a decrease in tannins, phytates and phenols in legume seeds after soaking in water for 24 hours.
During this study, the inclusion of treated (soaked and dehulled) Moringa oleifera seeds in the rations significantly increased crude protein intake compared to the ration containing untreated (whole) Moringa oleifera seeds. This could be explained by the fact that the technological treatments carried out on the Moringa oleifera seeds attenuated their negative effects of condensed tannins and phytates thus increasing the palatability of these rations. This is consistent with the work of  who reported a decrease in crude protein intake with the inclusion in rations of unconventional protein sources rich in anti-nutritional factors (Desmodium intortum and Arachis glabrata).
In the present study, no significant difference was observed between the different treatments for CUDa of BC DM and OM with fresh Pennisetum purpureum associated with the rations. This would be related to the small variation the proportions between the ingredients of the different rations, which accounts for the narrowness of the ration. This would be related to the small variation the proportions between the ingredients of the different rations, which accounts for the narrowness of the ration. Indeed, the different rations were iso-nitrogenated. The same observation was made by  ;  and  who reported that the inclusion of unconventional protein sources (Desmodium intortum, Arachis glabrata and Moringa oleifera) did not significantly affect the quality of the diet the apparent digestive utilization factor of DM, OM and CF. On the other hand, the digestibilities of the CP of the TEM + Pp and peeled + Pp rations were comparable and significantly higher than that of the MO-whole + Pp ration. This could be due to the treatment carried out on M. oleifera seeds which reduced their tannin content. Indeed, according to  and  the tannins present in the feed can form insoluble complexes with dietary proteins and thus decrease their digestibility or bind to digestive enzymes and inactivate them. These results are superior to those obtained by .
The study showed that the lowest levels of condensed tannins (8.2% MS) and total phenols (2884 mg/100gMS) were obtained with M. oleifera seeds soaked in water for 24 hours. Guinea pig ingestion of the granulated concentrate was higher (35.34 gMS) with the ration not containing Moringa oleifera seeds. In addition, the highest crude protein intake values were obtained respectively with the control ration (5.10% DM) and the ration containing peeled Moringa oleifera seeds (4.72% DM).
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