Effect of garlic meal on growth performance and carcass characteristics of indigenous Venda chickens

Indigenous chickens are economically, nutritionally and culturally very important in most rural areas (Swatson et al., 2001). Most of the chickens found in the rural areas are the indigenous breeds. To date, indigenous Venda chickens remain an important source of good quality meat and additional income for many rural households of South Africa (Hadjula, 2006). There is, therefore, a need to improve their productivity without compromising the meat attributes. The results of the studies carried out by Faruga and Jankowski (2000) indicated that garlic (Allium sativum) supplementation stimulate the immune reactions, thus reducing death and improves the performance of broiler chickens. Allium sativum used as single plant extracts or as mixed preparations has been reported to support both performance and health status of the chicken (Manzanilla et al., 2001). These can be attributed to bioactive components (allicin) present in garlic (Amagase et al., 2001). The extracts of this plants are used as feed supplements to improve growth performance in broiler chickens (Abdullah et al., 2010). Other studies did not find any improvement in broiler chicken productivity with garlic meal supplementation (Janvendel et al., 2008; Rahmatnejad et al., 2009; Ghasemi et al., 2010). There is, also, no agreement on supplementation levels of garlic meal for optimal productivity of broiler or on the indigenous chickens. Additionally, no studies were found on garlic meal supplementation effects on productivity of South African indigenous chickens. Thus, one possible nutritional strategy of improving productivity and reducing mortality in indigenous chickens may be supplementation with garlic meal. Therefore, the objective of this study was to determine the effect of garlic meal supplementation on feed intake, digestibility, and growth rate, feed conversion ratio, live weight, mortality and carcass characteristics of Venda chickens aged one to 13 weeks.

This study was conducted at the University of Limpopo Experimental Farm at Syferkuil, South Africa. The farm is located at about 10 km northwest of the Turfloop campus. The mean temperatures in winter (April to July) range between 10.1 and 28.4°C and in summer (August to March) between 18 and 36°C. The study was conducted between December, 2013 and March, 2014. The study commenced with 800-day-old chicks with an average weight of 30.25 ± 2 g and was carried out for a period of 13 weeks. A completely randomized design was used to randomly allocate the chicks to four garlic supplemented treatments with each treatment replicated ten times, thus, 40 floor pens were used in total. The chicks were fed a grower diet supplemented with different levels of garlic meal. The grower diet contained 880 g of DM/kg, 12.2 MJ of metabolisable energy/kg DM and 180 g CP/kg DM. The four treatments were as presented in Table 1. Light was provided 24 hours daily while feed and water were provided ad libitum throughout the experiment. The experiment was terminated when the chickens were 91 days old. The ingredients, nutrient composition of the grower diets and proximate analysis of garlic meal are presented in Table 2. All statistical analyses were performed using (SAS, 2012). Data were investigated with analysis of variance (ANOVA). General Linear Model procedures for statistical Duncan test for multiple comparisons was used to test the significance of differences between treatment means (P<0.05). The responses in feed intake, feed conversion ratio, live weight, growth rate, carcass weight and other carcass characteristics to level of garlic meal supplementation were modelled using the following equation:

 
                                Y = a + b₁x + b₂x²

 
Where Y = optimum feed intake, feed conversion ratio, live weight, growth rate and carcass characteristics, a = intercept, b1 and b2 = coefficients of quadratic equation, x = garlic meal level of supplementation and –b₁/2b₂ = x value for optimal response. The quadratic model was fitted to the experimental data by means of NLIN procedures of SAS (SAS, 2012). The quadratic model was used because it gave the best-fit model.
 

 

The results obtained from the effect of garlic meal supplementation on indigenous Venda chickens are presented on Tables 1, 3, 4, 5, 6 and 7, respectively. Results of this study indicate that garlic meal supplementation improved diet intake, growth rate, feed conversion ratio and live weight of unsexed Venda chickens aged one to 49 days. This is contrary to the results of Janvendel et al., (2008), Rahmatnejad et al., (2009) and Ghasemi et al., (2010) who did not find any effect of garlic meal supplementation on the performance of broiler chickens. However, Rahardja et al., (2010) reported that garlic meal supplementation at 1.2 and 4 % improved feed intake in pullets aged 4 weeks. Similarly, Kumar et al., (1991) reported that garlic meal supplementation increased weight gain, feed intake and feed conversion ratio of broiler chickens aged one to 21 days. However, these authors did not determine garlic meal level for optimal productivity of the chickens. The present results indicate that supplementation level of garlic meal 14.0 g/kg DM supported optimal feed intake of unsexed Venda chickens aged one to 49 days. This level is similar to 13.9 g/kg DM reported by Javandel et al., (2008) in broiler chickens aged one to 21 days. However, this value is contrary to the linear response observed by Rahardja et al., (2010) for pullets aged four weeks. Supplementation level of garlic meal 18.9 g/kg DM optimized growth rate of Venda chickens aged one to 49 days. This level however, is lower than the 43.9 g/kg DM reported by Javandel et al., (2008) in broiler chickens aged one to 21 days. Furthermore, Aji et al., (2011) reported a positive linear relationship between growth rate of broiler chickens and supplementation level of garlic meal, this might mean that the levels used by these authors were not high enough to optimize growth rate. Supplementation level of garlic meal 27.5 g/kg DM optimized feed conversion ratio of unsexed Venda chickens in the present study. This level is higher than 9.8 g/kg DM observed in the study conducted on broiler chickens aged one to 21 days by Javandel et al., (2008). This improvement might have been due to improvement in feed intake, feed conversion ratio and growth rate of chickens when supplemented with garlic meal. Live weight of unsexed Venda chickens was optimized at garlic meal supplementation level of 17.0 g/kg DM. Elagib et al., (2013) reported a higher spplementation level of 24.5 g/kg DM for live weights of broiler chickens aged 42 days.
 

 

 

 

 

               
Garlic meal supplementation improved feed intake, growth rate, feed conversion ratio and live weight of Venda chickens aged 50 to 91 days. These results differ from those of Ashayerizadeh et al., (2009) who reported that garlic meal supplementation did not have any effect on body weight gain and feed conversion ratio of broiler chickens aged 22 to 42 days. Similarly, Ghasemi et al., (2010) reported that inclusion of 0.1 and 0.2 % garlic meal to the diets of laying chickens aged three to eight weeks did not significantly affect their body weight gain and feed conversion ratio. A garlic meal supplementation level of 14.24 g/kg DM optimized carcass weight of Venda chickens aged 91 days. This level is higher than the 10.2 g/kg DM observed by Javandel et al., (2008) in broiler chickens aged 42 days; however, it is lower than the 21.4 g/kg DM recorded by Elagib et al., (2013) in broiler chickens aged 42 days. The dressing percent and thigh weights were optimized at a garlic meal supplementation level of 12.7 g/kg DM. The 12.7 g/kg DM level for dressing percent is lower than 18.25, 26.4 and 53.1 g of garlic meal/kg DM reported for broiler chickens by Elagib et al., (2013), Fadlalla et al., (2010) and Fayed et al., (2011), respectively. The difference could be attributed to the breeds used. The breast meat weight of Venda chickens, in the present study, was optimized at a garlic meal supplementation level of 11.2 g/kg DM. This is lower than the 21.4 g/kg DM observed in broiler chickens by Elagib et al., (2013).