Protein-energy malnutrition is prevalent in most African countries. Given the vulnerability of large livestock to climatic and health hazards, livestock production development strategies are paying more and more attention to short-cycle animals, including poultry, which occupy a special place [1] [2] . Indeed, poultry farming is seen as a means of investment or capitalization making it possible to mobilize funds when necessary, and in addition to satisfying the animal protein needs of populations [2] [3] . It represents an interesting source of proteins of high biological value and makes it possible to quantitatively and qualitatively improve the diet of populations [4] . Poultry farming is an important activity for the development of a country’s economy. In the Republic of Congo, poultry products (meat, eggs, milk and others) occupy an important place in household consumption. In fact, Congo imports approximately 50% of the total volume of animal products estimated at 45789.6 tonnes in 2007 [5] .

In addition, the productivity of local breed chicken remains low despite significant actions to support the sector in the areas of health (vaccination and deworming campaign), food and housing and even strategies marketing [6] . A growth rate of 3% is recorded, a carcass weight of 0.8 to 1 kg [7] and an annual laying of 27 eggs per hen per year [8] . Multifactorial causes generally contribute to this low productivity, among which reproduction figures prominently. Indeed, natural brooding remains the main means of obtaining chicks in traditional poultry farming [8] . The use of artificial brooding remains marginal, especially in rural areas due to the unavailability of incubators adapted to this environment, mainly due to the absence of electricity and the rising cost of oil.

The shortage of livestock feed in terms of quality and cost constitutes an obstacle to the development of monogastric breeding in Congo [9] . In fact, feed represents 70% to 80% of the cost of poultry production. However, the availability of conventional raw materials (soybeans, peanuts and their derivatives, fish meal, corn, etc.) for poultry production clashes not only with the diet of humans but also with that of monogastric species. Under these conditions, the search for and development of alternative food resources available locally in chicken feed should make it possible to improve their productivity [10] . Among these alternative food resources, Cajanus cajan leaves feature prominently. Indeed, flour from Cajanus cajan leaves is a local and easily accessible non-conventional food resource (RANC) in Congo. They are relatively energetic, rich in proteins (22% to 30% DM) and amino acids, minerals, vitamins. Pigeon peas are also low in fat, making them a food of choice in both human and animal nutrition. Its nutritional value is very close to that of beans or peas so appreciated by many peoples, and can be used as a supplement in the diet of chickens [11] .

Work carried out by [12] [13] showed that it is possible to improve the reproductive performance of hens by giving them conventional feed. However, the mobilization of conventional resources requires a fairly heavy investment which breeders in the sector almost do not have. However, there are unconventional food resources (Cajanus cajan; Cassia tora, Leucaena leucocephala, Moringa oleifera, etc.) that can replace conventional protein sources [14] [15] .

Studies carried out by various authors [12] [13] [16] - [19] showed that Cajanus cajan leaves are rich in nutrients, particularly proteins, minerals and vitamins. They have been incorporated up to 5% to 20% respectively in the feed of poultry, pigeons and guinea fowl without any harmful effect on the productivity and health status of the animals. It is in this context that this study was undertaken. The general objective of this work is to contribute to the search for ways and alternatives to improve the diet and productivity of hens.

The temperature during our experiment varied between 38˚C to 37.2˚C. The temperatures recorded at our incubator are similar to those (37.7˚C and 37.8˚C) reported by [20] [21] . These results indicate that the temperature varied slightly in a decreasing manner as time progressed. Our results are similar to those of [22] who believe that the optimal temperature must be maintained at 38.9˚C, during the first two weeks of incubation, and reduced to 36.1˚C from the 19th day of incubation because the chicks also produce heat. Our results are different from those of [23] , who thinks that this temperature should be between 39 and 39.5˚C (102˚f - 103˚f) and also be constant during incubation. According to [20] [21] , for incubators with forced ventilation, the ideal temperature for better development of the embryo and optimal hatching is 37.7˚C to 37.8˚C. This temperature is also decisive for the correct growth of the chick after hatching. Low temperatures delay hatching but are more dangerous than high temperatures [22] . Humidity varied in an increasing direction (60% to 70%). This development ensures the proper development of the embryo but also facilitates digging by making the shell more fragile. Our results corroborate those [20] [21] [24] , which stipulate that the best incubation results are obtained with a relative humidity of 50% to 60% during the first 18 days and at more than 75% during the last three days of incubation.

The fertility rates depending on the rations in our study varied significantly between 26.88% and 86.95%. This variation in fertility rates could be explained by the level of mobility and the breeding conditions which in a certain way caused stress to the animals. The most interesting rates (78% and 91%) have been reported in lighter breeding conditions [25] [26] . According to [22] [25] [27] , the sex ratio is generally one rooster for 10 hens with variations depending on the breed. [28] , rather recommends that to have good fertilization, it takes 8% to 8.5% of roosters of the number of hens to obtain 90% to 92% of fertilized eggs from the 26th week of age and 94% to 97% from the 28th week. In chickens, the higher the laying rate, the higher the percentage of fertile eggs. The hens that lay the most eggs would also be the ones that get the most attention [23] . The hatching rates obtained in this study are generally low and vary between 36.87% and 17.18%. This low hatching rate could be explained on the one hand by the untimely power outages causing variations in temperatures and relative humidity at the level of the incubator, and on the other hand by the rearing conditions of the breeders in experimental cages undoubtedly facilitating the breeding of females by males. Higher rates have been reported by various authors in Africa. Indeed, it would be 80% [29] [30] [31] respectively in Nigeria, Senegal and Cameroon. However, it shows a strong variation depending on the country. In Mali, it varies between 60% - 70% [32] and 42% - 80% in Guinea according to [33] . This variation would be due, in addition to possible errors linked to the data collection methodology, but also to the season. For this purpose, the hottest seasons would be the most unfavorable, undoubtedly because of the poor conservation of eggs due to high ambient temperatures [32] [34] .

The embryonic mortalities recorded in our study varied between 2.10% and 30.68%. These rates were significantly different depending on the treatments. This difference could be due on the one hand to power outages during the incubation period, consequently causing temperature variations, and on the other hand, to the frequency of relative humidity control during the incubation phase incubation. Note also that these high embryonic mortality rates could be the result of poor egg porosity in these batches. Indeed, too great a porosity would lead to excessive evaporation with the consequence of dehydration of the embryo and death, and too low porosity would cause insufficient evaporation and consequently the embryo dies by drowning.

The rates of unfertilized eggs in the different experimental batches varied between 72.20% and 12.03%. The high rates of unfertilized eggs in our study would undoubtedly be linked to the quality of the males. Indeed, males whose sexual characteristics of interest (absence of dewclaw, weakly developed and leaning crest, asymmetry of the barbels) in reproduction are not well developed must be excluded. In our study, the limited number of males did not allow for adequate selection.

Generally speaking, the incorporation of Cajanus cajan leaf flour into the ration of breeders did not cause any adverse effects on the health status of the chicks produced from the latter’s eggs. Indeed, no mortality was observed during the entire thirty (30) day study period. The 0% mortality rate suggests that the incorporation of sun-treated cajanus cajan leaf meal does not have negative impacts on the general functioning of the reproductive organs of chickens.

The leaves of Cajanus cajan, like those of other legumes, constitute an important source of nutrients. They are relatively rich in nutrients, particularly proteins, minerals and vitamins. They have a better benefit of essential amino acids (lysine, phenylalanine, valine, leucine and isoleucine). The grains are edible (India, Kenya, etc.) and rich in fatty acids, the main ones being linoleic acid and palmitic acid. Our study involved 219 eggs from 40 subjects fed Cajanus cajan leaf flour as a substitute for soybean meal at the ENSAF School farm. It appears from this study that the reproductive parameters of these laying hens are good. There was no difference between the two foods distributed (control and experimental) to the laying hens regarding the start of laying, the fertility rate of 86.95 (CC 15%); 43.95% (CC 5%); 33.20% (CC 10%) and 26.88 (CC %). A hatching rate of 36.8% (CC15%); 25.96 (CC 10%); 22.05 (CC 5%) and 17.18 (CC 0%), the shell mortality rate per batch was 2.10 (CC 10%); 10.74 (CC 0%); 19.28 (CC 5%) and 30.68 (CC 15%).

At the end of our study, we can conclude that the incorporation of Cajanus cajan leaf meal up to 15% in the reproduction type ration in hens, had no harmful effect on the reproduction performance of laying hens. Congo. On the contrary, it improved growth parameters and increased reproductive parameters. It did not cause any harmful effects on the health of the chicks produced from the latter. Taking into account the performances obtained in this study, it can be concluded that the incorporation of Cajanus cajan leaf meal can be recommended up to 15% in the breeding type feed in laying hens.

1) Summarize and comment on the challenges related to poultry farming:

In the Republic of Congo, despite a strong demand for poultry, the level of production remains low and does not cover the needs of the populations. This situation increases Congo’s dependence on the outside world for meat products, giving way to massive imports [35] (DJOMBO, 2016). Consequently, the quantity of imports increases every year, it was estimated at 200 billion in 2011 [36] (FAO, 2012). This deficit in meat products is linked not only to the low productivity of local breeds but also to the insufficient mastery of production techniques and to the demographic explosion that the Congo is experiencing [37] (AKOUANGO, 2010). To reverse this trend, the desire of the Congolese State is to ensure the sustainability of agricultural activities through the modernization of family farming towards commercial agriculture, that is to say, to make this sector more productive in order to diversify its economy [38] (PDAC, 2017). Since 2002, we have seen a revival of the poultry sector, particularly in peri-urban and rural areas. Despite these efforts, the poultry sector in Congo faces a food problem. The success of poultry farming depends on several factors including nutrition. These are, in a few lines, the challenges of poultry farming in the Republic of Congo.

2) Does the addition of Cajanus cajan leaf flour influence the nutritional components of eggs?

In order to answer this relevant question, our study did not evaluate the quality of eggs from chickens fed Cajanus cajan leaves. However, we raise this question as a perspective to determine the nutritional quality of eggs from chickens fed on Cajanus cajan leaves.

3) Does the addition of Cajanus cajan leaf meal influence the health of chickens?

In our study, it appears that the study of the survival of chicks from chickens fed on Cajanus cajan leaves showed a 0% chick mortality rate. From these results, we can conclude that the incorporation of Cajanus cajan leaves up to 15% does not influence the health status of poultry.