Effect of Graded Levels of Spirulina ( Arthropsira Platensis ) on Feed Intake and in vivo Digestibility of Trypsacum laxum in Guinea Pig ( Cavia Porcellus L )

The intake and in vivo digestibility of Trypsacumlaxum in guinea pigs according to the graded level of spirulina was evaluated in Cameroon. 20 animals aged of 6 months with an average weight of 450 ± 50 g were randomly divided into 4 equivalent groups. Each group received T. laxum and 40g of compound feed containing 0% (TS0), 2% (TS2), 4% (TS4), and 6% (TS6) of spirulina. Feed intake was the different between the left over and the quantity served. The sample of T. laxum and those of each diet as well as feces were collected and analyzed for the apparent digestibility of each nutrient. Animals were weighed at the beginning and at the end of each period of the test to determine the body weight gain. This study showed that the average daily intake of dry matter (DM) for TS0, TS2, TS4 and TS6 was 74.39 ± 2.98, 78.66 ± 3.14, 83.89 ± 4.28 and 77.76 ± 4.40 g/head/day. The highest apparent digestibility coefficients of different nutrients were obtained with animals fed TS6 group while the lowest were observed in TS0.The apparent digestibility coefficient of dry matter (DM), organic matter (OM) and crude protein (CP) of the supplemented group were statistically higher than those of the control diet. Animals’ weight performances were statistically comparable between treatments. Thus, the combination of T. laxum with concentrated feed containing spirulina can be recommended for guinea-pigs, but the level of incorporation may not exceed 4% of its daily ration.


Introduction
Food insecurity in general and protein shortage in particular is a real problem in African countries [1]. The deficit in animals protein due to the increasing population have led to the search for other sources of readily available and more affordable protein sources of animal origin [2]. Guinea pig is favored as alternative [1,3], because of its high growth rate, low fat and protein-rich meat that constitutes a major advantage of production [4,5]. In addition, it is a secondary source of income. In fact, breeding is an important asset [6] that can address several food and socio-economic issues in low-income families [7]. Despite these advantages of guinea pigs, in Cameroon, its production remains weak because of several constraints including food management. The animals are fed on kitchen waste and crop residues. This situation does not allow this monogastric herbivore to satisfy the needs of its caecal flora and externalize its genetic potential [8]. Improvement in guinea pig productivity can be achieved through a balanced diet [9,10], with dietary protein being the most important component of production cost and at the same time the limiting factor. The high cost of concentrates commonly used as protein supplement in guinea pigs, [11][12][13] leads to higher cost of production and does not always make it possible to obtain a good productivity [7]. The search for other sources of supplements available and assimilable by the animal, including green supplements [13] is more necessary, to optimize the use of T. laxum and keep animals in acceptable performance [12]. However, many legumes can be used, but generally adapted to rodents, due to concentration of anti-nutritional factors in the plants [14]. Spirulina because of its high protein content (60 to 75%) and its high digestibility (75 to 80%) could be a protein source to improve productivity and reduce the cost of production. Unfortunately, very little research on spirulina has been initiated or published on the rationalization of food use in cavies. It is in this perspective that this study was undertaken to evaluate the effect of four levels of supplementation with spirulina on the in vivo digestibility of T. laxum.

Experimental Design
The guinea pigs were randomly distributed into During the test, samples of 100 g of experimental feed and feces from each animal were taken daily and dried at 60 ° C to constant weight in a ventilated oven and milled to determine the digestibility of nutrients. At the end of the test, animals were fasted for 12 hours, and then sacrificed by cervical dislocation followed by bleeding. They were then dressed at the abdominal area and then eviscerated. The caecum was removed, sectioned, and their content was put into sterile tube to evaluate the caecal flora constitution according to the method described by Benson [15].
Weighing was made using a digital scale balance with a capacity of 3 kg and a precision of 1 g. At the end of the study, mean values of feed intake, average daily gain, and apparent digestibility coefficients of nutrients were determined.

Chemical Analysis of Feed and Faces
The dry matter (DM) and organic matterwas determined by drying 0.5 g of sample in an oven overnight at 100 ° C, ash was obtained by incineration at 500 ° C for 6 hours and organic matter (AOAC, 1990).
Crude fiber (CF) was determined using the sheerer method and crude protein (CP) by the Kjeldahl method by AOAC [16]. Apparent digestibility coefficients (ADC) were determined by the following formula: x 100

Statistical Analyses
Feed intake, apparent digestibility coefficients and caecal flora constitution data were subjected to one-way analysis of variance. When significant differences existed between treatments, the separation of means was done by the Duncan test at 5% significance level [17]. SPPS 20.0 software was used.

Animal Weight Performance
Total weight gain and daily weight gains during digestibility were comparable between treatments.
Mean total weight gain and mean total daily weight gain were highest in TS4 group animals, while the lowest was record with TS6 animals (Figure 1).

Constitution of Guinea Pig Ceacal Flora.
The effect of spirulina level on the composition of the guinea-pig flora is illustrated by the     [11], Ramirez-Riviera et al. [12], Peiretti and Meineri [18], Noumbissi et al. [19] and Fotna [20] who showed that the inclusion of protein source increased feed intake. This result shows the good palatability of spirulina in guinea pigs. Indeed, Marie-Christine [21] showed that supplementation with spirulina in the diet of pigs, poultry and broilers improve their acceptability, palatability and digestibility.
In the case of cellulolytic microflora, its nutrients would be better digested, thereby accelerating the digestive transit [2,23]. This has the effect of pushing the animal to consume more. Indeed, Quigley and Poppi [24] showed that spirulina has the potential to increase the production of microorganisms and reduce and Noumbissi et al. [19], but lower than 73.7 and 103.21; 115.80 and 170.9 g DM/head/day) obtained by Kouakou et al. [11] and Egena et al. [23] and Getachew [27] on sheep, Kouakou et al. [11]in guinea pigs fed P. maximum and supplemented with Euphorbia heterophylla and Noumbissi et al. [19]. This can be explained by the fact that, protein intake of spirulina would have stimulated palatability of guinea pigs.
Moreover, several works by Razafindrajoana et al. [22] and Marie-Christine [21]   Tsukahara [29], Miégoué et al. [5,30]. These authors reported that, guinea pig normal flora is predominantly anaerobic gram (+), grams (-) being present in lesser quantities. Spirulina can therefore be used as a source of protein in guinea pigs' diet without, however, running the risk of altering the composition of the caecal flora, which is generally unstable in order to ensure better digestibility of the nutrients. Losson [31] showed Spirulina supplementation therefore tends to modulate the colonization of the digestive tract by microbial populations involved in the gut microbiota homeostasis.

Conclusion
The effect of graded levels of spirulina on ingestion, in vivo digestibility and caecal flora of guinea pig (Cavia porcellus) were evaluated. From this study, it appears that the level of spirulina: • Influenced intake of T. laxum, compound feed, dry matter (DM), organic matter (OM), crude fiber (CF) and crude protein (CP); • Improved apparent digestibility of different nutrients; • Did not influence caecal flora but allowed their balance by modulating different ceacal flora populations; • The administration of spirulina at the rate of 4% seem to be appropriate for guinea pig feeding but further investigation is necessary before using level above.
Spirulina is a blue-green algae that grows naturally on Lake Tchad and its use as an alternative source of nitrogen in guinea pigs fed on forage of low nutritional quality should be vulgarized.

Conflict of Interest
There are no conflict of interest among authors for this article.