1.       Introduction

Caviaculture has the characteristics of an economically profitable mini-farm and can there for effectively deal with protein malnutrition in Africa in general and in Cameroon in particular [1,2]. However, this mini breeding very prolific, easily manageable and inexpensive knows a low production and productivity in Cameroon due to a diet essentially based on cooked residues. Food plays a role of choice in breeding in general and caviaculture in particular Appropriates food and their well management will improve guinea pig production [3]. However, the guinea pig is a monogastric herbivore in which the fibers are essential [4]. These fibers are provided by forages including grasses like Panicum maximum and Pennisetum purpureum which are by their availability, their palatability, their value and the absence of antinutritional factors, the two most commonly used animal feeding in general and guinea pig food in particular [5]. Better integration of these two grasses despite their current use remains a challenge for the breeder [6]. Hence the need to evaluate the forage potential of Panicum maximum and Pennisetum purpureum in caviaculture.

2.       Methods

The study was conducted between December 2016 and May 2017 at the Research and Application Farm (FAR) of the University of Dschang, Located in the Western Highlands Cameroon at an altitude of 1420m, at the east longitude of 09^° 85' 10^° 06' and at the northern latitude from 5^° 36' to 5^° 44'. This region receives 1500 to 2000mm of water per year with a temperature average of 18^°C between July-August and 25^°C between February-March. Its relative humidity varies from 40 to 97% with an insolation of 1800 hours. The climate is equatorial of the Cameroonian type altitude with a long rainy season from mid-November to mid-March and a short dry season from mid-March to mid-November.

 24 weaned (3 weeks after birth) guinea pigs of comparable weight were divided into two homogeneous lots of 12 (5 females and 7 males) animals each. The animals were raised in two boxes made of plywood (1m long, 0.8m wide and 0.6m high) each equipped with lighting and electric heating equipped with 2 feeders in wood for the concentrated feed and two concrete water troughs in one of the livestock buildings made at the Research and Application Farm of University of Dschang. The animals were raised on the ground, on a litter made of wood chips dry untreated 5cm thick, renewed every 2 days to avoid accumulation of feces and urine. The different lodges were equipped with a cover of small mesh to protect animals from mice and other predators that may accidentally enter the livestock building.

The plant material was Panicum maximum and Pennisetum purpureum grasses harvested at the pre-bloom stage on the FAR farm, pre-faded before being directly serve to animals. A sample of 100 g of each feed as well as the food compound (Table 1) was collected dried at 60^°C to constant weight in a ventilated oven of mark Gallemkamp. The samples were subsequently crushed to 1 mm mesh and kept in plastic bags for different bromatological analyzes (Table 2).

At weaning, the females were removed from the boxes. The young were sexed and followed up to 8 weeks of age. Each animal was identified by a numbered metal buckle carried on his ear. The animals of each lodge received each day between 8am and 9am Ad libitum the grass and 20g of a compound food which was composed using ingredients purchased from dealers of agricultural byproducts of the city of Dschang (Pennisetum purpureum Ad libitum + 20g compound food / animal / day; Panicum maximum Ad libitum + 20g compound food / animal / day). Vitamin C was dissolved in drinking water and served with it (at 240 mg in 1.5 liters of water). At the end of the test, 5 animals were randomly select in each lodge, fasted for 12h, slaughtered by cervical dislocation and bleed totally in the throat and eviscerated for the evaluation of carcass characteristics and the proportion of some organs of the digestive tract.

2.1.  Collection of Data

Every morning, refusals food and droppings were cleaned before any new food distribution. Animal weighing were done weekly until the 8th week. This made it possible to determine the post-weaning weight evolution.

They following parameters were then determined:

·         The weight of the classic carcass (PCl = Live weight at slaughter + Weight (blood + head + legs + viscera).

·         Commercial carcass (PCco = live weight at slaughter - weight (blood + head + legs + viscera).

·         The weight of faith, intestine and cecum were determined as follows:

·         Weight of organ or part = 100 (weight of organ or part / live weight at slaughter).

·         All weighing was carried out using a digital scale of 7kg of capacity and sensitivity of 1g.

·         For reproduction, the following parameters were evaluated.

2.2.  Statistical Analyzes

Data on growth performance and carcass characteristics were tested using Student test 5% level of significant and SPSS 19.0 software was used.

3.       Results

3.1.  Comparative Effect of Panicum Maximum or Pennisetum Purpureum on the Evolution of Post-Weaning Guinea Pigs Weight

The average weight has progressively increased regardless to the grass use with time (Figure 1). Hence, no significant difference (P > 0, 05) was observed between the weight of post-weaning pigs feed with P. maximum and those feed with Pennisetum purpureum.

3.2.  Comparative effect of Panicum maximum or Pennisetum purpureum on the weight evolution of post-weaning female’s pigs

The weight of post-weaning females progressively increased regardless to the grass use with time (Figure 2). However, no significant difference (P > 0, 05) was observed between the weight of post-weaning pigs feed with P. maximum and those feed with Pennisetum purpureum during the period.

3.3.  Comparative effect of Panicum maximum or Pennisetum purpureum on weight evolution of post-weaning young males

The weight of post-weaning males increased regardless to the grass use (Figure 3). However, no significant difference (P> 0.05) was observed between weight of males fed with P. maximum, and males fed with Pennisetum purpureum during this period.

3.4.  Comparative effect of Panicum maximum or Pennisetum purpureum on total gains and average daily gains of young post-weaned guinea pigs

Weaning weights were significantly (P 0.05) higher in females and regardless of sex when animals were fed with P. maximum (Table 3). At 8 weeks, no significant differences (P> 0.05) were observed between body weights of animals whatever the sex and the grass used. Although comparable in females, total gains and ADGs was significantly (P 0.05) higher in males and regardless of sex with Pennisetum purpureum.

3.5.  Comparative effect of Panicum maximum or Pennisetum purpureum on carcass characteristics of guinea pigs.

Weights (live, heart, digestive tract, carcass and carcass) classic) were comparable (P> 0.05) between animals fed with P. maximum or Pennisetum purpureum (Table 4). On the other hand, the weight of the head of pigs fed on Pennisetum purpureum were significantly (P 0.05) higher than that of guinea pigs fed with P. maximum. Apart from the weight of the classic carcass which was higher with Pennisetum purpureum, the other characteristics had higher values in guinea pigs fed with P. maximum although no significant difference (P> 0.05) was observed between the two grasses. The proportion of the head and the digestive tract compared to live weight were comparable (P> 0.05) for both forage. The alimentation with Pennisetum purpureum gave liver proportions in relation to body weight significantly (P 0.05) higher.

3.6.  Weight and length of some digestive organs in guinea pigs fed with Panicum maximum or Pennisetum purpureum

Liver weight, large intestine length, and small intestine density were significantly (P 0.05) higher in animals fed with Pennisetum purpureum (Table 5). On the other hand, no significant difference (P> 0.05) was observed between weight of the large intestine, small intestine and caecum of animals fed with P. maximum or Pennisetum purpureum. The large intestine was significantly (P 0.05) longer in animals fed with Pennisetum purpureum. While, the lengths of the small intestine and caecum were comparable (P> 0.05) between the two grasses.

4.       Discussion

The average weight of animals at 8 weeks was comparable between the two grasses. This shows that animals have valued Panicum maximum as well as Pennisetum purpureum. Indeed, after weaning, the piglets would have acquired a greater capacity to value any kind of forage with regard to their herbivorous diet. This would have favored a digestion of the grass regardless of the type of forage. In fact, [7] more the animal is getting older the more it has the ability to better value the cellulose contained in the feed. The highest average weight 332.67g obtained with Panicum maximum in females and 330.16g registered in males fed with Pennisetum purpureum is less than 342.42g for P. purpureum and 337.67g for P. maximum obtained in young animals supplemented with a ration containing Arachis glabrata [8]. This weight is greater than 214 g and 216 g observed respectively with 16% and 18% of protein at the 8-week-old guinea pig [9]. This difference can be explained by the form of presentation of the grass. Indeed, in these last authors, Pennisetum purpureum had been dried, crushed and incorporated into the other ingredients while in this study the animals receive it fresh (leaves and stems).

Weight gain and ADG of guinea pigs receiving Pennisetum purpureum were significantly higher than those of animals fed with Panicum maximum at 8 weeks of age regardless of sex. This is explained by the chemical composition of Pennisetum purpureum whose was better compared to that of Panicum maximum. Pennisetum purpureum would therefore be better suited for meeting the needs of animals after weaning. Our value obtained in this study (4.16 g) is less than 4.94 g obtained [8] in guinea pigs supplemented with Arachis glabrata. This will be explained by the low protein content of our rations. Comparative effect of P. purpureum or P. maximum on guinea pig weights at slaughter and carcass yields live weight of animals at slaughter were comparable for both grasses. However, the highest weight (302.6g) was recorded with P. purpureum. This observation justifies the high bromatological value of P. purpureum compared to P. maximum. This observation is similar to that of [8] in guinea pigs supplemented with different sources of legumes.

The carcass weights while being comparable for both grasses were higher (116.33g) with P.maximum for the commercial carcass and (178.80 g) with P. purpureum for the conventional carcass. The highest live weight (302.6g) obtained in this study is lower than that of the animals fed with diets containing D. intortum (408.40g for P. purpureum and, 426.60g for P. maximum) obtained [8] but remains above 221 ± 11g recorded [9] with 16% protein ration. This difference can be explained by the fact that our grass was served fresh. The highest carcass weight (116.33g for the conventional carcass and 178.80g for the commercial carcass) obtained in this study is greater than 99.3 ± 3.3g observed [9] in male guinea pigs fed with a 16% protein ration. It is, however, less than 202.6 to 246.0g obtained [10] in hybrids from the cross between male and female Bukavu. This would be due to the genetic difference with the animals used in the context of this study. P. maximum gave better carcass yield regardless of the type of carcass.

The highest carcass yield (47.68% for P. purpureum and 49.28% for P. maximum) obtained in the animals submitted to the diets containing D. intortum [8] are higher than 35.10% for P. purpureum and 40.62% for P. maximum obtained in this study. Our numbers are also lower than the 43.5 ± 1.7% and.9% respectively obtained [9] with male guinea pigs fed with a 16% protein diet and [10] in hybrids from the cross between male and female Bukavu. This would be due to the difference in protein level and the low genetic potential of our animals. Compared effect of P. purpureum or P. maximum on some organs involved in digestion in the guinea pig. The weight of the liver, the length of the large intestine and the density of the intestine were significantly higher with P. purpureum. This difference would be related to the bromatological value of this grass indeed according to Atuahéné et al. (1986), the weight of the 5th neighborhood increases with the level of fiber in the food.

Animals fed with P. purpureum had the highest ceacal weight (38.40g). This could be due to the high cellulose content of P. purpureum (34.78g / MS against 33.08g / MS in P. maximum) used in this study. Our results are in agreement with those of [8] who noted in guinea-pigs supplemented with legumes the highest caecum weight compared to the control batch. Similarly, the values ​​ (32.9 ± 1.7g, 29.2 ± 2.3g and 26.3 ± 2.5g) recorded [9] respectively with 14, 16 and 18% protein show that the weight of cecum drops with increasing protein level or lower fiber level food ration. Thus, guinea pigs fed with P. purpureum would have ingested more fiber which would have promoted the development of organs involved in digestion. In fact, in guinea pigs, as in most pseudo-ruminants, caecum is the organ strongly involved in the digestion of cellulose because it houses the microbial flora able to digest cellulose. Thus, the more the food is fibrous, the more microorganisms are solicited and reciprocally the development of the cecum follows. The cecum is indeed [11], the rumen equivalent in ruminants.

Conclusion

This study shows that:

·         The weight of the pigs at 8th week was comparable for both grasses;

·         Pennisetum purpureum gave better weight gains from weaning at 8th week of age;

·         Panicum maximum gave better carcass yields and low organ weights compared to Pennisetum purpureum. 

PM: Panicum maximum, PP: Pennisetum purpureum.

Figure 1: Comparative effect of Panicum maximum or Pennisetum purpureum on the evolution of post-weaning guinea pigs weight.

PM: Panicum maximum, PP: Pennisetum purpureum.

Figure 2: Comparative effect of Panicum maximum or Pennisetum purpureum on the growth evolution of post-weaning female’s pigs.

Figure 3: Comparative effect of Panicum maximum or Pennisetum purpureum on weight evolution of post-weaning young males.

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