Growth and carcass performances of guinea fowls reared under intensive system in Benin

P V Houndonougbo, R R Mota, A A C Chrysostome¹, J Bindelle, H Hammami and N Gengler

University of Liège, Gembloux Agro-Bio Tech Faculty, TERRA Teaching and Research Centre, B-5030 Gembloux, Belgium
rrmota@ulg.ac.be
¹ University of Abomey-Calavi, Agricultural Science Faculty, Animal Production Department, 03BP 2819 Cotonou, Benin

Abstract

Several local guinea fowl varieties continued to be reared in extensive systems in Benin, even though productivity remains low. Improving rearing conditions through feeding and housing may enhance local guinea fowls productivity in Benin. Therefore, the objective of this study was to verify growth and carcass performances of five (Common, Bonaparte, Grey, White and Black) local guinea fowl varieties under intensive management conditions. At birth, 36 keets (young guinea fowls) of each identified variety were randomly divided into six batches and reared up to 16 weeks old under the same feeding and housing conditions. Body weights were recorded up to week 15. At week 16, carcass measurements were also taken.

Growth performances and carcass measurements (morphological and visceral) differed among guinea fowl varieties. The  heaviest body weight was observed in Common (832±24g)  and the lowest in Black variety (698±39g). Highest carcass yield was observed in Grey variety. Liver weight, intestine length and caecum length were highest in Bonaparte variety. Gizzard weight and thigh proportion were highest in Common variety.  Breast weight and breast proportion were highest in Grey guinea fowls. Body weight was moderately correlated with drumstick length, body length, wing size, tarsus diameter, thigh length and thorax circumference (range r = 0.34-0.60). The phenotypic variability and its impact on the characterization of these varieties implies that they are genetically different strains, supporting the hypothesis that the guinea fowl population in Benin presents opportunities for genetic improvement.

Key words: genetic correlation, genetic improvement, management condition, phenotypic variability, productivity

Introduction

As a rural poultry enterprise, the production of guinea fowl has potential to become more profitable in intensive than extensive management systems (Adeyeye and Aremu 2010; Agbolosu et al 2014). The importance of the guinea fowl production is evident in West Africa: domesticated animals are widely exploited, provide high quality of protein and play an important social and cultural role (Dahouda et al 2009; Sanfo et al 2012). However, the remained low guinea fowl productivity may result from low performances and profitability achievements under extensive management systems. Improving rearing conditions through feeding and housing may enhance local guinea fowls productivity in Benin.

Genetic improvement via selection is also an important tool that must be considered (Boko et al 2013; Dahouda et al 2009; Sanfo et al 2012).The growth performance variability under extensive systems have already been reported (Dahouda et al 2009; Halbouche et al 2010; Nahashon et al 2010; Sanfo et al 2012). All of these authors have pointed out the genetic variability between guinea fowl varieties and their nutritional requirements.

On the other hand, to our knowledge, studies comparing growth and carcass performances between guinea fowls in Benin remain unknown. Therefore, the objective of this study was to verify growth and carcass performances of five (Common, Bonaparte, Grey, White and Black) local guinea fowl varieties under intensive management conditions. The following assumptions were made: the first hypothesis was that growth performance differed among varieties, the second that carcass measurements (morphological and visceral) also differed among varieties, and the final hypothesis stipulated that body and carcass measurements differences were crucial to characterize guinea fowl varieties in Benin.

Materials and methods

Five genetic varieties of guinea fowls (Common, Bonaparte, Grey, White and Black) commonly reared in Benin were used in this study. Their names are normally based on plumage color. Therefore, plumage color and also the presence of spots were used to differentiate them (Figure 1).

Figure 1. Guinea fowls varieties named based on plumage color: Commona,b;Bonapartec,d;Whitee,f; Black g,h; Grayi,j. Source Houndonougbo et al (2017).

Ninety fertilized eggs were incubated for each variety. The eggs were originated through individual intra-variety mating performed in village farms and thus, high degree of purity could be expected for each variety. At hatch, 58 guinea keets (young guinea fowls) were obtained per variety. At this moment, due to batch availability, only 36 out of 58 were randomly sorted and divided into six homogeneous batches. This procedure was done separately for each variety. As long as sex identification in guinea fowls can only been done very late (14 weeks old), neither sex identification nor sex balance were performed at hatch. However, after 14 weeks old, the sex identification was performed in order to consider this variable as a fixed effect in the statistical model. The guinea fowls were identified by numbered rings. The groups of six were randomly distributed in a chicken coop with 36 boxes of 0.4 m². After two months, the animals were randomly transferred into metal cages to be raised until 16 weeks old. These birds received the same feeding management. No humidity and temperature control were possible. Therefore, the observed temperature ranged between 23.5°C and 27.7°C, while relative humidity rate was between 70% and 95%.

Physical and chemical composition of the diets offered to birds is presented in Table 1. From week 0 to 16, each bird received 6,580g of food, being 1,050g and 5,530g, respectively in the starter and grower phases. In this period, body weights, feathers color and presence of spots and/or pearls were recorded. At week 16, growth and carcass measurements were analyzed. Twelve animals of 16 weeks old were slaughtered for carcass yields (morphological and visceral) evaluation. The studied growth and carcass traits were: body weight, body length, wing size, boneless drumstick proportion, boneless drumstick weight, boneless thigh proportion, boneless thigh weight, breast circumference, breast length, breast proportion with bone, breast weight with bone, caecum length, carcass yield, drumstick length, drumstick proportion with bone, drumstick weight with bone, gizzard weight, heart weight, intestine length, liver weight, slaughter weight, tarsus diameter, tarsus length, thigh proportion with bone, thigh weight with bone, thorax circumference.

The growth performances were analyzed by using Statistical Analysis System software (SAS, 2002). The GLM procedure of SAS was used for variance analysis. The test of Fisher was used to determine the significance of variety and sex effects. Based on the estimated correlations between the studied traits, Principal Components Analysis (PCA) was used on body measurements recorded at week 16 to further highlight traits that better characterizes the Guinea fowl varieties.

Results and discussion

As shown in Figure 2, the least square mean body weight of guinea fowls was, in general, similar among varieties. Note that there was a slight superiority of Bonaparte up to week six and Common starting at week eight, whereas the lowest performance was observed in Black. At week 16, no significant differences were observed among varieties (range 906-1029g). Few studies have been compared varieties over ages. Fajemilehin (2010) confirmed the relative superiority of Common variety (called Pearl in this study) at advanced ages. Nevertheless, the least square mean body weights in this study were higher than those reported by Fajemilehin (2010). At week eight, this author reported body weights of 276g, 294g and 258g for Common, Grey (called Ash) and Black varieties, respectively. The results in this study were also higher than the values reported by Nahashon et al (2009), Sanfo et al (2009) (range 197g and 227g in both studies) and by Sanfo et al (2012) in Burkina Faso (values around 200g). On the other hand, the results were similar to those reported by Dovonou et al (2009) (range 365g to 416g). In general, body weight measures at weeks 12 and 16 were higher than those in literature (Dahouda et al 2009; Dovonou et al 2009; Fajemilehin 2010; Sanfo et al 2012; Sanfo et al 2009). However, these results were lower than those obtained in improved guinea fowls raised in France (Nahashon et al 2007; Laudadio et al 2012). The growth curves of the studied varieties did not reached the asymptomatic point at week 16 and justified the results reported by Sanfo et al (2009). These authors obtained asymptomatic point at week 22. It can be inferred that animals normally do not reach their full growth potential in 16 weeks of experimentation. Therefore, improvement in their performances may be only achieved by raising them under controlled feeding and housing conditions. This last hypothesis is consistent with Halbouche et al (2010), who reported least square mean body weights of 1,008g at 90 days old in local guinea fowls.

Figure 2. Growth curves for different varieties of local guinea fowls raised under intensive system in Benin.

 The Bonaparte variety showed the highest values for six carcaa traits (Table 2): On the other hand, the Common variety presented highest values for five of them. The Grey variety presented the highest values for breast weight with bone, breast proportion with bone, carcass yield and tarsus length whereas the Black variety had the highest breast circumference and drumstick bone proportion.

In summary, Grey and Black carcass yields were the highest (85.1% to 79.2%), while body weights were the lowest values. The carcass yields found herein were higher than those reported by Sanfo et al (2008) at the same age (75.7%). Moreover, our values were also higher than those observed by Nobo et al (2012) at 13 weeks old (74.1% in males and 75.8% in females). The carcass yields found in the present study were also higher than the 70.0% reported by Laudadio et al (2012), but similar with Nahashon et al (2009) (range 72.9%-76.5%). These not expected results in this study might be explained by the low level of fat in our guinea fowls. The observed differences in carcass yields may depend upon bone and muscle proportion.

The animals were reared under the same environmental conditions and agro-ecological area in Benin as in Tougan et al (2013a). These authors characterized the five local ecotypes of chicken as Holli, Fulani, Sahoue, South and North. They also reported some variability between them. It implies that differences between the five varieties in our study may be an indicator of genetic variability among varieties.

The study of Denbow et al (2000) revealed that fast-growing Leghorn chickens have longer intestine length than slow-growing (179 cm vs. 108 cm). Although our results are lower than this reported in chickens, they partially supported the hypothesis that slow-growing guinea fowls (Black; 90 cm) had shorter intestine than fast-growing (Bonaparte; 103 cm). This is a valid hypothesis even though significant differences in intestine length between fast-growing Common and slow-growing Black guinea fowls were not observed.

Growth and carcass measurements of local guinea fowls can be observed in Table 3. There were no differences for least square mean body weights, drumstick length and thigh length among varieties. However, two varieties showed distinct features: Common, with higher body length and larger wing size, and Grey, with higher tarsus length, tarsus diameter and thorax circumference. There were differences between sexes for body weight, tarsus length, tarsus diameter and wing size. Males were heavier and presented longer and thicker tarsus as well as greater wing size.

Differences between carcass traits were previously reported in five local chicken ecotypes in Benin (Tougan et al 2013b). It was confirmed the same behavior in all studied guinea fowl varieties. Fajemilehin (2010) studied the same varieties and found smaller differences in tarsus length. These results were lower than those reported by Nsoso et al (2006) in improved 12 weeks old guinea fowls in Botswana. The Grey and Black varieties used herein had the lowest least square mean weight, but highest tarsus length and carcass yield. These results are confirmed by the negative correlation reported between tarsus length and body weight. The positive correlation between tarsus length and thorax circumference showed the interdependence between them.

The phenotypic correlations (r) between/within growth and carcass traits recorded at week 16 week are presented in Table 4. Many traits showed from high to very high correlations. Overall, the body weight of guinea fowls was moderate to high correlated with drumstick length, body length, wing size, tarsus diameter, thigh length and thorax circumference (0.34 ≤ r ≤ 0.60). The drumstick length was high correlated with tarsus diameter and thorax circumference (r = 0.64) and moderately correlated (0.29 ≤ r ≤ 0.38) with body length and wing size. The tarsus length was high and positively correlated with tarsus diameter (r = 0.40) and thorax circumference (r = 0.70) as well as negatively and moderate correlated with body length (r = -0.30) and wing size (r = -0.17). The thigh length was high and positively correlated with body length (r = 0.50), as wing size was with body length (r = 0.39) and thorax circumference (r = 0.45).

The first, second, third and fourth eigenvalues of the correlation matrix for growth/carcass measurements represented 40.4%, 25.5%, 10.1% and 7.50% of the initial variance, respectively. The first axis (eigenvector) representing the first eigenvalue was high and positively correlated with all studied traits (range 0.58-0.77), except with tarsus length (r = 0.06) and tarsus length (r = 0.40). The second axis differentiated animals characterized by drumstick length, tarsus length, tarsus diameter and thorax perimeter from animals characterized by body weight, thigh length, body length, and wing size. Finally, the third axis discriminated animals characterized by body weight, tarsus diameter and wing size from the other studied traits.

It appeared that tarsus length, tarsus diameter, body length, thorax circumference and wing size could be used for local guinea fowl characterization in Benin. The principal component analysis (PCA) showed that the four first axes expressed 83.5% of total variability. The representation quality by axis and for the first factorial indicated that the first axis is positively correlated with all studied traits and did not allow animal regrouping. However, the second axis discriminated animals characterized by using body weight, thigh length, body length and wing size from animals characterized by using drumstick length, tarsus length, tarsus diameter and thorax circumference. Slight differences were indicated between heavier (Common and Bonaparte) and lighter (Grey and Black) varieties. It is important to highlight that even if animals came from rather pure strains, the guinea fowl varieties are generally reared in free range altogether and the admixture generated by inter-varietal mating becomes genetic and phenotypic differentiation complex.

Conclusion

• The phenotypic variability observed and their impact on variety characterization enabled to suspect that they are genetically different strains.
  
  
• However, the mixing of these birds in traditional farms, where they are generally reared in free range system, generates admixture between these strains.
  
  
• The results also support the hypothesis that the guinea fowl population in Benin presents large opportunities for genetic improvement based on their phenotypic variability.

Acknowledgement

The authors thank the government of Benin for its financial contribution. The authors are also very much grateful to the Animal Sciences Unit of Gembloux Agro Bio Tech (University of Liege) for all types of supporting activities.

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Received 12 July 2017; Accepted 25 August 2017; Published 3 October 2017

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