A comparative study of growth (Body weight and linear body measurements; Neck length, Body length, Thigh length, Shank length and Breast width) and seasonal influence on some reproductive hormones (luteinizing hormone (LH), progesterone (P4) and estradiol (E2) and egg production in two strains of guinea fowl (Belgie and Pearl) was conducted at the Poultry Unit, Teaching and Research Farm of the Department of Animal Science, Faculty of Agriculture, Ahmadu Bello University, Zaria, Kaduna State. Body weight and linear body measurements were taken biweekly from 16 weeks to 28 weeks of age. The year was classified into four seasons; late dry (January, February and March); early rain (April, May and June); late rain (July, August and September) and early dry (October, November and December). Level of reproductive hormones and egg production were assessed in each season. There was a significant (P<0.05) strain effect on body weight throughout the experimental period, mean body weight ranged from 488.13 ± 8.84 to 1057 ± 9.3g and 309.35 ± 7.4 to 782.86 ± 7.16g in Belgie and Pearl strains, respectively. There was also significant (P<0.05) difference in linear body measurements at different ages with Belgie having the highest value in all the parameters measured. Season had significant (P<0.05) effect on hormonal level with highest figure obtained in the late rainy season. Means for the hormonal assay in the late rainy season were LH-4.670 ± 0.25, P4– 1.390 ± 0.11, E2- 2.000 ± 0.2 and LH- 5.060 ± 0.2, P4– 1.970 ± 0.08 and \E2- 1.860 ± 0.19 in Belgie and Pearl, respectively. There was no egg production in season one; late dry. Total egg produced during the late rainy season was significantly (P<0.05) higher than what was produced in the other seasons in the two strains. Correlation coefficients for body weight and linear body measurements were positive and high in Belgie; BDL 0.804, BRW 0.955, NKL 0.765, THL 0.857, SHL 0.826 while in Pearl, they were positive and high in breast width 0.903, thigh length 0.884 and neck length 0.892 but low in back length 0.268 and shank length 0.252.
Correlation coefficients for season and hormones were positive and high during the late rainy season; LH 0.546, P4 0.771, E2 0.828 while that of season and egg number was positive and low. Belgie strain can be improved upon for better growth traits while Pearl for better egg production trait.
Malnutrition has been a persistent problem in Africa especially Nigeria. The most important area of deficiency is in the intake of animal proteins. Guinea fowl (Numida meleagris) meat and egg contribute immensely to the alleviation of this animal protein deficiency with demand being higher than supply and can be a tool for poverty reduction (Koney, 2004). Attractive plumage and value as a table bird with game-type flavor and higher meat to bone ratio of guinea fowl has led to its worldwide acceptance (Embury, 2001). They are widely consumed by a large number of Nigerians because of the meat and egg which possess distinct flavor and taste (Ayeni and Ayanda; 1982).
Guinea fowl production is associated with small holder farmers in Africa and is described as ”poor man‟s pheasant” (Smith, 2000). It has ambiguitous distribution in Africa where it has distinct popularity among small holder farmers (Nwagu and Alawa 1995). This specie of poultry is kept for various purposes depending on the society. Like chicken, guinea fowls are a source of protein (Embury, 2001). Other advantages of rearing guinea fowl include; low production cost, greater capacity to utilize green feeds, control of ticks and other pests and better ability to protect itself against predators and fewer requirements for labour and management (Sayila, 2009). However, egg production is seasonal in guinea fowls (Ogwuegbu et al., 1988). Sonaiya and Swan (2004) also reported that guinea fowls are seasonal breeders, laying eggs only during rainy season, under free range conditions. This is because successful poultry species instinctively lay and incubate their eggs at a time of the year when newly hatched chicks will have a better supply of high protein and energy food provided by the environment. Saina et al. (2005) reported 5±1 months breeding season in Zimbabwe, Southern Africa
The seasonality of production has been recognized as one of the major problems that may hinder large scale commercial guinea fowl production. Factors responsible for this seasonality are however not yet clearly known. Progesterone, estradiol and luteinizing hormone are the most important steroid hormones affecting reproduction in livestock and poultry and have been reported to be positively related to egg production in turkeys (Mashaly et al., 1979). Tanabe et al. (1981) reported a positive correlation between circulatory levels of progesterone and estradiol in egg production in laying hens in a pure-line. The preovulatory rise in plasma progesterone and estradiol precede and stimulate the rise in luteinizing hormone and there is a positive feedback reaction between progesterone, estradiol and luteinizing hormone that induces ovulation (Kanoth and Sharp, 1998). Adeyinka et al. (2007) reported a positive correlation between circulatory level of progesterone and egg production in guinea fowls Numida meleagris galeata.
The live body weight of any animal is an important variable that determines market value of that animal. There is variation in growth performance of different strains of guinea fowl (Fajemalehin 2010). The exact time at which the animal is ready for slaughter can be assessed on the basis of its body weight and general development (Akanno and Ibe, 2006). Age is a major determinant of growth and physiological development in livestock (Assan, 2013).
Linear body measurement helps in comparison of growth in different parts of the body. It has been severally used to characterize strains, evaluate carcass yield, sex performance and predict live weight gain in livestock (Oke et al., 2014). Linear body measurements have a recurring interest to livestock production either to supplement body weight as a measure of productivity or as predictors of some less visible characteristics (Sapriyantono et al., 2012).
Body weight has direct relation to the production and profitability of any livestock enterprise. Body weight measurement is used the most to evaluate body development in livestock and
poultry production (De Brito Ferreira et al., 2000), but it is not easily measured in the field. Several studies have shown that body weight has a direct relationship with morphometric characteristics and carcass traits in poultry (Ogah, 2011).
The strong relationship existing between body weight and linear body measurements may be useful as selection criteria, since positive correlations of traits suggest that they are under the same gene action (pleiotropy) (Kabir et al., 2006; Aziz and Al-Hur, 2013). This study was undertaken to compare the body weight and morphometric traits and seasonal influence on some reproductive hormones and egg production in two strains of guinea fowl in a humid rainforest zone.
It has well been identified that very little is done in terms of scientific research into the production, management and improvement of the indigenous guinea fowls as compared to domestic chicken (Magaga and Haule, 1994).
Studies investigating the difference existing in growth performance and egg production among different strains of guinea fowls, have focused on nutrition (Jones et al. 2010, Nahashon et al. 2007) and on the effect of housing system (Yamak et al. 2016).
Growth performance in guinea fowls may also be affected by genetic effect while egg production apart from genetic effect may be affected by season and reproductive hormones availability. Therefore, the present study is aimed at comparing the growth performance and seasonal influence on some reproductive hormones (LH, P4, E2) and egg production in two strains of guinea fowls (Belgie and Pearl).
1.2 Objectives of the Study
- To compare the growth performance (Body weight and linear body measurements) of Belgie and Pearl strains of guinea fowl.
- To assess the effect of season on some reproductive hormones (progesterone, estradiol and luteinizing hormones) and egg production between the two strains of guinea fowls (Belgie and Pearl).
1.3 Research Hypotheses
Null hypotheses (Hₒ): There is a significant difference between body weight and linear body measurements in Belgie and Pearl strains of guinea fowl.
Alternative hypotheses (Hₐ): There is no significant difference between body weight and linear body measurements in Belgie and Pearl strains of guinea fowl.
Null hypotheses (Hₒ): Season has no significant effect on some reproductive hormones (luteinizing hormone, progesterone and estradiol) and egg production in Belgie and Pearl strains of guinea fowl.
Alternative hypotheses (Hₐ): Season has significant effect on some reproductive hormones (luteinizing hormone, progesterone and estradiol) and egg production in Belgie and Pearl strains of guinea fowl.