Most of the developing countries are found in the tropics and are experiencing rapid urbanization [1]. The dominant issues to address are food security and nutrition, combating rural poverty to enhance rates and patterns of agricultural growth can contribute to economic development and environmental protection [1]. Most of the malnutrition seen in the world is as a result of relying too heavily on a few staple foods [2]. It is however difficult to obtain such variety but meat can complement most diets especially those dependent on a limited selection of plant foods. Contributions from sustainable increase in livestock and poultry production will therefore be desired in order to meet the demands of the human population for quality protein supply. It has been estimated that it will be necessary to increase meat production by 80 percent between 2000 and 2030 [3].

Rural poultry production over the years had centered on local chickens [4]. The local chicken contributes immensely to protein availability for rural communities, being the major source of meat than other protein providing products [5]. Rural poultry production had also support crop agriculture when sales of chickens are made to support rural farmers’ revenue input to crop production or as a cushion when revenues expected from crop production are not feasible [6]. Rural farming communities of over 90 percent in developing countries reared local chickens on free range production systems [4]. This system of rural poultry production is not only affordable to the rural farming communities, but had also fitted into cultural and socio-economic lives of farming communities in the developing nations [7].

As important as the rural poultry production is in developing nations, value chain intervention and value addition strategies had not been introduced to the rural farming communities for adoption to improve revenue for the rural farming communities [8]. In view of these, the rural poultry production had not been able to provide its maximal support to rural farming communities [8]. Disease epidemics, unimproved housing and poor nutrition have over the years being a challenge limiting full utilization of the potential of the rural poultry sector in developing countries [9]. Aside value chain and value addition interventions, diversifying rural poultry production by introduction of unconventional poultry breeds like the French broiler guinea fowl will also provide improved support for the rural poultry production subsector.

Apart from body weight, a number of conformity traits are known to be good indicators of body growth and market value of guinea fowls [10]. Poultry breeders have tried to establish the relationship that exists between body weight and body linear measurements such as shank length, thigh length, keel length, body length, chest circumference and wing length. The relationships between these traits provide useful information on the performance and carcass value of the animals [11]. The relationship between body weight and body linear measurements is important for selection in breeding programs for genetic improvement of the breed [12]. The use of body linear measurements to predict body weight of different species of animals have been attempted by various researchers [13-15], however, there is little information on the prediction of body weight of poultry using body linear measurements [16].

The objectives of this study were to determine the relationships between body weight and body linear measurements of the French broiler guinea fowl raised in the humid tropics of Nigeria and to model the relationship between body weight and body linear measurements of the French broiler guinea fowl.

Location of study

This study was carried out in Makurdi, Benue State, Nigeria. Makurdi lies on latitude 7°30’ 22’’ N and longitude 9°21’ 22’’E with a climate typical of the tropical zone, Makurdi has two distinct seasons. The wet season; which ranges from April to October and the dry season which ranges from November to March with an annual rainfall range from 508 mm to 1016 mm. The annual temperature ranges from 22.8°C to 40°C with annual relative humidity range of 47% to 87%.

Experimental design, birds and their management

The experimental design used was the randomized complete block design (RCBD). About 86 French broiler guinea fowl keets at 5 weeks of age were transferred to the rearing pen measuring 5 m×5 m dwarf walled with wire mesh, aluminum roofing sheet and cemented floor and wood shaving was used as litter material at a 2 cm depth. The birds were given anti stress (Vitalite®) on arrival through drinking water. They were fed commercial grower diet containing 18% crude protein while feed and water were provided ad libitum. The French broiler guinea fowls were dewormed at 32 weeks to control endo-parasites, cleaning of feeding and watering equipment’s were carried out daily while litter materials were changed routinely.

Experimental procedure

Body weight measurement: Body weight of the individual birds was measured by placing the guinea fowl on a digital sensitive scale and taken weight in grams.

Body linear measurements: The Shank length, thigh length, keel length, chest circumference, body length and wing length were measured using a flexible measuring tape graduated in centimeters. Shank length was measured by taking the distance between the foot pad and hock joint. Thigh length was measured by measuring the distance between the hock joint and the tidio-fibula-fumoral joint. Keel length was measured by taking the distance between the anterior and posterior ends of the Keel. Chest circumference was taken by measuring the circumference of the body around the breast region. Body length was taken by measuring the distance between the phygostle and the last posterior vertebrate. Wing length was taken by measuring the distance between the tips of the phallenges to the scapula joint.

Data collection and analysis: Data were collected on thirty eight weeks old French broiler guinea fowls. Descriptive statistics was employed to measure the mean and standard error using Minitab 18. The relationship between body weight and body linear measurements was determined using Pearson’s product moment correlation (r). Linear regression of body linear parameters on body weight was also performed using the following simple and multiple linear regression equations.

Y=B+β₁X₁ (1)

Simple regression equation

Where;

Y=dependent variable (Body weight).

B=the intercept

X1=independent variable

Y=Dependent variable (Body weight).

B=B+β₁X₁+β₂X₂ …β_kX_k (2)

Multiple regression equation

Where;

Y=the intercept

Β_s=the slope

Xs=independent variables (SL, TL, KL, CC, BL, WL).

Average body weight and body linear parameters

The mean values of body weight and body linear parameters are presented on Table 1. Body linear parameters ranged from 7.76 ± 0.53 cm to 23.53 ± 2.14 cm with shank length showing the least and body length shows the highest measurement.

Table 1:  Mean Values of Body Linear Parameters of the Broiler Guinea Fowl

Correlations between body weight and body linear measurements of the French broiler guinea fowl

The correlations between body weight and body linear measurements of the French broiler guinea fowls are presented on Table 2. Body weight and body linear measurements had (P<0.01) associations.

Table 2:  Correlation between Body weight and body Linear Measurement of the French Broiler Guinea Fowl

Prediction equation relating to body weight and body linear parameters

Prediction equation relating to body weight and body linear parameters is presented on Table 3. Body weight had significant (P<0.01) associations with body linear parameters. The values of the coefficient of determination (R2) ranged from 0.2% to 19.4%.

Table 3: Predictive equations and strength of prediction for body weight of the French broiler guinea fowl

Body weight and body linear parameter

The mean value for body weight observed in this study was higher than the values 1.23 g, 1.13 g and 1.28 g for pearl grey, peal grey pied and white guinea fowls in Ghana reported by Brown et al. [17]. This could be that the French broiler guinea fowl is an improved strain compared to pearl grey, peal grey pied and white guinea fowls. Mean shank length observed in this study was also higher than the value reported by Kasperska et al. [18] but lower than the range of 8.88 ± 3.1 cm to 9.31 ± 4.7 cm reported by Panyoka et al. [19] for domestic and wild helmeted guinea fowl of Kenya. Brown et al. [17] also reported higher values for local guinea fowl in Ghana. Differences observed in this study could be attributed to differences in breeds, levels of improvement, environmental factors and management practices employed. Mean thigh length value observed in this study was higher than the value of 11.57 ± 0.01 reported by Ogah [20] for indigenous guinea fowl of Nigeria. This could be that the French broiler guinea fowl is an improved strain compared to the indigenous guinea fowl of Nigeria. Mean keel length in this study was higher than the value of 11.57 ± 0.10cm reported by Ogah [20] and Brown et al. [17] for pearl grey, peal grey pied and white guinea fowls in Ghana. This could also be that the French broiler guinea fowl is an improved strain with broader body linear parts compared to the indigenous guinea fowl of Nigeria. Mean chest circumference reported in this study was higher than the mean value (26.85 cm) reported by Brown et al. [17] for local guinea fowl in Ghana. This could be because of the superior genome of the French broiler guinea fowl. Mean wing length and body length reported in this study were lower than the values reported by Panyoka et al. [19] for guinea fowls in Kenya. This could be as a result of uncontrolled mating system and breeding objectives which must have led to loss in hybrid vigor.

Correlations between body weight and body linear measurements

Body weight and body linear measurements had positive association in this study. That is, there existed a positive correlation between body weight and body linear parameters. This is in agreement with reports by Ukwu et al. [10] who reported high and positive correlation between body weight and body linear measurements in the Nigerian chicken, the report of Momoh and Kenshima [16] using Nigerian local chicken also agrees with the result of this study. Findings in this study indicated that shank length and chest circumference had the strongest correlations with body weight as compared to other body linear parameters. This corroborates with the results of Ojo et al. [21] who investigated the relationship between body weight and linear body measurements in Japanese quails. This implies that an improvement in shank length and chest circumference will lead to a corresponding improvement in body weight. The observed effect may be due to pleiotropic effect and gene linkage effects between the two traits of the French broiler guinea fowl. Selection for body weight gain could be achieving selection for shank length and chest circumference.

Prediction of body weight using body linear parameters

The significant and positive associations among body weight and body linear parameters, indicated by the prediction equations showed that, the predictive equations could be used to predict body weight with high accuracy. The highest coefficient of determination of shank length indicated that it has the highest accuracy to predict body weight compared to the other body linear measurements. R² values in this study were lower than those reported by Ukwu et al. [10] and Momoh and Kenshima [16] for Nigerian local chicken. This could be due to the effects of breeds determining body parts dimensions, environments and management systems employed.

Conclusion

The results of this study indicated that there were strong and positive correlations between body weight and body linear parameters. The study also indicated that body weight can be predicted using body linear parameters. Shank length had the highest capacity and accuracy to predict body weight compared to the other body linear measurements. This was followed by chest circumference. This relationship could be used in selection programs for genetic improvement of body weight gain in the populations of the French broiler guinea fowl raised in Nigeria. Thus, breeding program designed for genetic improvement of body weight gain in the populations of the broiler guinea fowl can apply selection to shank length and chest circumference as selection criteria.

From the results of the study, the following recommendations were drawn.

The strong relationship between body weight and body linear measurement can be exploited for genetic improvement of body weight gain of the broiler guinea fowl strains. Selection for body weight gain can be achieved by selection for shank length to explore the correlated association between these traits.