The study was undertaken at the University of Dschang Research and Application Farm (FAR) and in the laboratory of Animal Nutrition of the University of Dschang with the following geographical coordinates: 5°44’-5°36’ and 5°44’-5°37’ Latitude North; 10°06’-9°94’ and 10°06’-9°85’Longitude East and an altitude of 1394 m in the Western Region of Cameroon. It has a Cameronian climate with an altitude characterized by a short dry season (mid-November to mid-March) and a long rainy season (mid-March to mid-November). Rainfalls vary between 1500 and 2000mm per year with an average of 1800mm and an average temperature of 22°C 17.

The study was conducted within a special building of 50 m² which protects the animals from rain, sun; excessive cold and predators while providing them light with good ventilation. In this building, 96 guinea pigs were uniformly distributed in 12 boxes (of 7.2 m²) separated with the help of plywood placed on cemented floor. Six (6) boxes were covered with a layer of litter made of white wood chip and six were without litter.

96 (48 males and 48 females) adult guinea pigs (Caviaporcellus) weighing 390 ± 110 g averagely were used. These animals were randomly distributed into two lots and maintained in 12 identical boxes of 0.6 m² each (4 males and 4 females of comparable weight per box). From these 12 boxes, six (6) had a floor covered with 375g of litter and six had an empty floor. Within 12 weeks (3 months), these 96 individuals were reared and fed 3times/day (7-7:30am, 12-12:30 and 5:30-6pm) with Brachariaruziziensis, Trypsacumlaxum, Panicum maximum, Pennisetumclandestinum, Pennisetum purpureum, Arachis glabata, Desmodiumintortum, and Calliandracalothirsus. The guinea pigs dungs were collected after 3 days at the same time between 6 to 7 am within the experimentation period. After cleaning the boxes, the dungs from the floor without litter were separated from feed debris and weighed while those from the floor with litter were equally separated from feed debris and weighed with litter using and electric scale (CAMRY). The weight of the dungs from the littered floor was then separated from that of the initial litter in other to evaluate the quantity of dung produced. After this collection, three samples per lot were taken for bromatological analysis in the laboratory of Animal Nutrition of the Faculty of Agronomy and Agricultural Science (FASA) of the University of Dschang as described by Kjeldhal 18 in other to determine the nitrogen and phosphorus content as described by Pauwels et al19. The analysis helped in evaluating the quantity of dungs necessary for the fertilization of a fish pond with a known area and to know the number of guinea pig to be reared in a fish pond with a known area.

At the end of the experiment, the total quantity of dung collected from the littered floor was determined. This quantity deduced from that of the litter helped to determine the exact quantity of dung produced by the animals. In the second lot without litter, the calculation method was the same with the exact quantity of dung produced directly obtained without litter.

In other to compare the differences between the nature of the floor and the breeding boxes for the collection of dungs of guinea pigs, the different data collected were subjected to the test of student. The Ducan test was used to separate means at a threshold significance of 1% when there was significant different between the means. The SPSS 21.0 software was used for the analysis.

(Table 1) shows the productivity of guinea pigs dungs by animal reared on a littered and empty floor respectively.

The quantity of dungs collected was greater when the floor was covered with litter. Hence, 60.53±0.64g and 51.69±0.36g of dung/guinea pig/day were respectively collected from a littered and empty floor. This weight difference is significant at a threshold of 1% (p˂0.01). This might be due to the fact that the litter that absorbed urine was not taken into consideration during the weighing of the weight and calculations. Urine has good nitrogen content. It would be therefore appropriate to advise farmers to collect dungs from a littered floor. Hence, not only the biomass would be high, but also the nitrogen content.

The daily dry matter productivity of guinea pig dung per animal is summarized in Table 2

The percentage of dry matter is high with or without litter (94.28%) which is an evidence of low moisture content of 5.72%. Hence, the dungs of guinea-pigs present a good content of dry matter available for the production of planktonic biomass and the direct feeding of fish species in heterotrophy ponds. This is in accordance with the works of Dabbadie et al 20 which stipulate that when an organic particle enters water, it future doubles. It is either consumed directly by heterotrophic especially some fish or degraded to release mineral elements which permits the production of phytoplankton by photosynthesis. However, FAO, 21, Dabbadie et al 20 and Pouomogne 22 determined the maximum safety level of animal organic matter in cool and temperate climate of 0.6kg DM/j/100m² fish pond and in hot and tropical climates of 1.2 kg DM/100m²/j fish pond.

The different chemical components of the guinea pigs dungs are presented in Table 3 and Table 4.

(Table 3) summarizes the crude protein, ash and organic matter contents of dungs. The different percentages of the crude protein, ash and organic matter are respectively 10.65%; 19.89% and 80.01%. This explains the richness of these dungs in nutritive elements which are available for the feeding of different fish species. The crude protein content (10.65%) in the guinea pigs dungs corroborates with the results obtained by Friote 23 and Pouomogne 24 on the crude protein content of some plants and fruits often used for the feeding of fish and fertilization. They explained that crude protein contents between 6 and 26% give good yields. This high content of organic matter (80.01%) is largely greater than 15% obtained with pig manure and slightly less than 88% in chicken droppings obtained by Efole 25. This content (80.01%) of organic matter is high for the fertilization of fish ponds in other to stimulate the natural production of phytoplankton and zooplankton.

After the conversion of percentages into grams, it is noted that in 51.69g of dungs produced, there exist 11.74g of nitrogen and 0.38g of phosphorus. The high quantity of nitrogen noted in the dungs can be due to the high protein content of feed. Therefore, these dungs can be of great aquaculture interest as the N/P ratio of the inputs is an important factor for the organic fertilization of fish ponds. According to Pouomogne et al 22, the nitrogen and phosphorus quantities in water have to be 1mg/l and 0.5 mg/l respectively. Moreover, in Thaïland having weather conditions (average temperature=25°c, average altitude=1778.33m) similar to that of the Western Region of Cameroon Knud-Hansen 26 noted that there is no universal recipe for the maximum rate of nitrogen and phosphorus fertilization because of the variability of fish ponds (every fish pond has its specificity). However, Knud-Hansen 26 stated that this rate might be around 30kg of nitrogen/ha/week and 10kg of phosphorus/ha/week in the breeding of tilapia that is 42.85 g/day/100 m2 and 14.28 g/day necessary /100 m² respectively. Lin et al 27 proposed contributions made between 20 and 40g of nitrogen/100m²/day. Also, Edward 28 noted that in Thaïland 2 to 4 kg of organic nitrogen /ha/day are necessary for the production of 7.3 and 10.95 tons of fish/ha/year in the breeding of tilapia. According to the nitrogen production by guinea pigs and propositions of the above mentioned authors, 2 to 4 guinea pigs/day/100m²is necessary for the individuals to produce 20 to 40g of nitrogen/day as recommended by Lin et al 27 and Edward 28. These animals have to produce between 88.06 to 176.12 g of dungs per day. These numbers can give an expected result of 10.21tons of fish/ha/year. However, according to Dabbadie and Lazard 20, during integration, the number of animals varies with the intensification level, weight and age of the animals.