NUTRIENT DIGESTIBILITY AND GROWTH PERFORMANCE OF BROILER CHICKENS FED PROCESSED TROPICAL SICKLEPOD (SENNA OBTUSIFOLIA (L.)) SEED MEAL BASED-DIETS

The eight-week feeding trial was conducted to evaluate the nutrient digestibility and growth performance of broiler chickens fed raw or processed Senna obtusifolia seed meal (SOSM). Six experimental diets were compounded to contain 0% SOSM and 20% each of the raw, boiled, soaked, sprouted and fermented SOSM respectively. Two hundred and sixteen (216) broiler chicks were randomly allotted to six (6) dietary treatments in a randomised complete block design with three (3) replicates containing 12 chicks each. Data were collected on nutrient digestibility, feed intake, weight gain, feed conversion ratio and mortality. The result of productive performance indicated that feed intake, weight gain and feed conversion ratio were significantly (P<0.05) depressed in broiler chickens fed raw, soaked and sprouted Senna obtusifolia seed meal. However, broiler chickens fed fermented SOSM showed better (P<0.05) productive performance that was close to those fed the positive control diet (0% SOSM). The mortality rate did not reveal any particular trend. However, the low mortality rate recorded in the different treatments indicated broiler chicken can tolerate up to 20% of either raw or processed SOSM. Broiler chickens fed raw SOSM recorded lower values for dry matter (63.06%), crude protein (52.46%), ether extract (53.88%), crude fibre (30.72%) and nitrogen-free extract (46.11%) digestibility than those fed the other processed SOSM. The nutrient digestibility of broiler chickens fed fermented SOSM was significantly (P<0.05) better followed by those fed boiled Senna obtusifolia seed meal. For instance, broiler chickens fed fermented Senna obtusifolia seed meal recorded the highest crude protein and ether extract of 69.91 and 70.03% compared to the other processing methods. It can be concluded that 20% fermented SOSM can be incorporated in the diets of broiler chickens with Corresponding author: e-mail: audaggai@gmail.com Augustine Clement et al. 372 acceptable depreciation in biological performance. Slightly lower levels of boiled SOSM can be included in the diet of broiler chickens but the levels should be ascertained in further studies.


Introduction
The high cost of feeds is the major challenge responsible for the slow growth rate of the Nigerian poultry industry. This is attributed to the scarcity and high cost of conventional protein sources such as soya bean and groundnut cake (Igene et al., 2012). Ukachukwu and Osuagwu (2006) have further reported that feed which accounted for 70% of costs of intensively reared poultry is a major limiting factor to the growth of the poultry industry. Therefore, the search for a cheaper alternative protein source is very necessary. Senna obtusifolia seed is one of such alternative that has been neglected in feeding poultry. The proximate composition of the seed as reported by Ingweye et al. (2010) has revealed that it has protein content of 29.54%, which suggests that it may be a good feed source for poultry. Senna obtusifolia seed contains some anti-nutritional factors such as tannins and alkaloid which will affect the digestibility and utilization of nutrients (Augustine et al., 2014). These anti-nutritional factors may be harmful to livestock when consumed beyond certain threshed hold. Therefore, before recommending Senna obtusifolia seeds as a feed ingredient for poultry, it is important to evaluate the best processing method(s) that will enhance the utilisation of the seed. Information on processing method(s) that will optimally improve the utilisation of Senna obtusifolia seed is scanty hence the need to bridge such information gap. This study was therefore conducted to evaluate nutrient digestibility and growth productive performance of broiler chickens fed raw or processed Senna obtusifolia seed meals.

Materials and Methods
The research was conducted at the Poultry Unit of the Department of Animal Production, Livestock Teaching and Research Farm, Adamawa State University. It is located between latitudes 9°30' and 11° north of the equator and longitudes 13° and 13° 45' east of the Greenwich meridian. The temperature regime in Mubi area is warm to hot throughout the year, however, there is usually a slight cold period between November and February. There is a gradual increase in temperature from January to April. The minimum and maximum temperatures of the area are 18.1°C and 32.8°C. The mean annual rainfall ranges from 900 to 1050 mm (Adebayo, 2004). Nutrient digestibility and growth performance of broiler chickens 373 Experimental stock and their management Two hundred and sixteen (216) day-old broiler chicks (Anak strain) were brooded and managed in deep litter pens of 0.06 m 2 /bird. The broiler chickens were vaccinated against Gumboro (2 and 4 weeks of age) and Newcastle disease (3 and 5 weeks of age). The experimental broiler starter diet was fed ad-libitum to the chicks for 35 days while the broiler finisher diet was fed for the remaining twenty one (21) days, respectively. Clean drinking water was similarly supplied ad-libitum throughout the period of the experiment.

Processing of Senna obtusifolia seeds
Senna obtusifolia seeds were divided into five batches. The first batch was left unprocessed (raw). The second batch was soaked in water for 24 hours. The third batch was boiled in water for 1 hour. The fourth sample was soaked in water for 48 hours and thereafter removed, washed, drained and spread on a jute sack and allowed to sprout. The fifth batch was cooked and placed in an air-tight container and allowed to ferment for 5 days. The differently processed Senna obtusifolia seeds were properly sun-dried and milled.

Experimental diets (treatments) and experimental design
Raw and differently processed Senna obtusifolia seed meals (soaked, boiled, sprouted and fermented) were included at 20% level each in the diets of broiler chickens at both starter and finisher stages (Tables 1 and 2). There were all together six treatment diets designated T1, T2, T3, T4, T5 and T6. Diet T1 contained 0% Senna obtusifolia seed meal and therefore served as the positive control while diet T2 contained raw Senna obtusifolia seed meal and served as the negative control. Diets T3, T4, T5 and T6 contained soaked, boiled, sprouted and fermented Senna obtusifolia seed meals, respectively. The 216 broiler chickens were randomly allotted to the six dietary treatments in a randomised complete block design (RCBD). Each treatment group was replicated three times with 12 chickens per replicate. The starter and finisher phases of the experiment lasted for 35 and 21 days, respectively.

Chemical analysis
The experimental diets were analysed for proximate composition and level of anti-nutritional factors using standard procedure as described by AOAC (2004).The dry matter content was determined using the oven dry method and crude protein was determined using the Kjeldahl method. The soxhlet extraction method was used for the determination of ether extract. The fibre content was evaluated using the trichloroacetic method. The tannins and total phenols were determined using the Folin-Denis method as described by Doss et al. (2011). 75 Vitamin -Mineral Premix (Animal Care) supplies the following per 2.5 kg: Vitamin A 12,000,000 vit. D 3 3000,000, vit. E30,000 mg vit. K 3 2,500 mg, folic acid 1,000 mg, niacin 40,000, calpan 10,000 mg, vit. B 2 5000 mg, vit. B 12 20 mg, vit. B 1 2,000 mg, vit. B 6 3,500 mg, biotin 80 mg, antioxidant 125,000 mg, cobalt 250 mg, selenium 250 mg, iodine 1,200 mg, iron 40,000 mg, manganese 70,000 mg, copper 8,000 mg, zinc 60,000 mg and chloride 200,000 mg. **Metabolisable energy (ME) calculated according to the formula of Pauzenga (1985)

Measurement of productive parameters and mortality rate
Daily feed intake was determined by the difference between daily feed offered and daily feed leftover. Final weight was taken at the end of the experiment and the overall weight gain was obtained by subtracting the initial weight from the final weight. Feed conversion ratio (FCR) was calculated using the formula shown below: FCR = feed intake weight gain Mortality rate was recorded as it occurred. Augustine Clement et al. 376 Determination of nutrient digestibility At the last week of the experiment, three (3) broiler chickens were randomly selected from each replicate and placed in individual battery cages for the digestibility study. The birds were allowed a three-day adjustment period. Measured quantity of feed was given to each bird every morning and the leftover weighed the next morning to calculate feed intake by each bird. Faecal collection lasted for three days. Faecal samples collected from each treatment group were bulked, milled and analysed for proximate composition according to the procedure of AOAC (2004). Nutrient digestibility coefficient (NDC) was calculated using the formula shown below: (NDC%) = (Nutrient in diet x feed intake) -(Nutrient in faeces x faecal output) x 100% Nutrient in diet x feed intake.

Statistical analysis
Data obtained were subjected to analysis of variance (ANOVA) of the randomised complete block design (RCBD) using Statistix 9.0 (Statistix 2003). A significant difference was considered at the 95% confidence level.

Results and Discussion
The results of the proximate composition of the experimental broiler starter and finisher diets are presented in Tables 3 and 4, respectively. The crude proteins for the starter and finisher diets were close to the values (23 and 20% respectively) for starter and finisher diets recommended by Aduku (1995) as the optimum protein requirement for broiler chickens in the tropics. The metabolisable energy contents of the diets ranged from 2883.80 to 2912.44 kcal/kg for the starter diets and 2903.02 to 3119.39 kcal/kg for the finisher diets. These values were close to the values (2800 kcal/kg) for broiler starter diets and (3000 kcal/kg) for broiler finisher diets recommended by Aduku (1995) as the energy requirements of broiler chickens in the tropics.
The levels of tannins and total phenols of the experimental diets revealed that these anti-nutritional factors were relatively high in the diets containing raw Senna obtusifolia seed meal compared to the positive control diet (0% RSOSM) and diets containing 20% of each of boiled, soaked, sprouted and fermented Senna obtusifolia seed meals. This is an indication that the different processing methods used were effective in reducing the levels of the anti-nutritional factors. These findings concurred with the earlier report of Udedibie and Nkwocha (1990) who found processing methods such as soaking, boiling and fermentation to be effective in reducing anti-nutritional factors in legume grains.  The productive performances of broiler chickens fed raw or processed Senna obtusifolia seed meals (PSOSM) are presented in Table 5. Final live weight and overall weight gain indicated significant (P<0.05) variation among the treatment groups. The average final live weight and overall weight gain of the broiler chickens fed raw Senna obtusifolia seed meal (RSOSM) were the lowest (P<0.05) compared to the other groups fed the processed Senna obtusifolia seed meals. This could be attributed to the negative effects of anti-nutritional factors such as tannins, oxalates and phytates present in the seed meal. This finding is in line with the report of Emiola et al. (2013) who fed raw mucuna seed meal to broiler chickens and observed a similar depressive effect on the growth of the chickens. The average final live weight and overall weight gain of the broiler chickens fed processed seed meal showed improvement in growth performance compared to the group of chickens fed the raw seed meal. This indicates that the different processing methods used reduced the level of the anti-nutritional factors to tolerable levels. This also concurred with the observations made by some researchers (Orgyeret al., 2009;Udensi et al., 2010;Tuleun et al., 2011;Emiola et al., 2013) who used soaking, boiling and fermentation methods as processing methods for pigeon pea and mucuna seeds and reported a significant reduction in the level of anti-nutritional factors. Table 5. Productive performance of broiler chickens fed raw or processed Senna obtusifolia seed meals.   The broiler chickens fed the fermented seed meal (FSOSM) had better (P<0.05) overall weight gain followed by those fed the boiled and sprouted Senna obtusifolia seed meal based diets. This concurred with the results obtained by Tuleun et al. (2011) who observed boiling and fermentation to be more effective in detoxification of anti-nutritional factors. Hong et al. (2004) reported that fermented soya bean meal had high protein content and amino acid composition. This may be the reason for the better performance observed in the group of broiler chickens fed FSOSM. Hirabayashi (1998) has further pointed out that inclusion of fermented feeds in poultry diets improves nutrient digestibility and growth performance. Udedibie et al. (1996) attested that boiling was very effective in reducing saponins compared to soaking in water. The superior performance (P<0.05) recorded in broiler chickens fed BSOSM and FSOSM indicated that boiling and fermentation as processing methods proved to be very effective in detoxifying the antinutritional components present in Senna obtusifolia seed meal. In a similar study, Tuleun et al. (2011) fed broiler chickens fermented mucuna seed meal based diet and reported better performance of the chickens. The superior (P<0.05) performance of broiler chickens fed FSOSM may be attributed to improvement in the crude protein content of the seed meal and possibly due to microbial protein that is usually associated with fermented materials as reported by Yashim et al. (2009). Ilyas et al. (1995 have further pointed out that fermented feeds contain biologically active by-products such as probiotic bacteria and lactic acid which exert some beneficial effects in the body of poultry. Daily weight gain showed a similar trend as that of overall weight gain. The feed intake and feed conversion ratio of broiler chickens fed the different experimental diets showed significant (P<0.05) variations. The feed intake and feed conversion ratio of broiler chickens fed FSOSM were higher (P<0.05) followed by those of the chickens fed BSOSM. The differences in the performance of broiler chickens fed boiled, soaked, sprouted and fermented Senna obtusifolia seed meals could be attributed to differences in levels of residual anti-nutritional factors in the diets. A similar finding was reported by Emiola et al. (2013), who fed processed mucuna seed meal to broiler chickens. Broiler chickens fed raw Senna obtusifolia recorded the lowest values for dry matter, crude protein, ether extract, crude fibre and nitrogen-free extract digestibility than those fed the other processed Senna obtusifolia seed meal.
The poor (P<0.05) nutrient digestibility observed in broiler chickens fed RSOSM could be attributed to the adverse effects of tannins and other related polyphenols present in the raw seed meal. This conformed to earlier observation made by Amaefule et al. (2011), who fed broiler chickens raw pigeon pea meal based diet and reported depressed nutrient digestibility. Furthermore, Reed (1995) pointed out that anti-nutritional factors can bind with protein in diets and form less digestible complexes and they may also combine with endogenous enzymes and thus depress digestibility. The broiler chickens fed the positive control diet (0% SOSM) exhibited superior (P<0.05) nutrient digestibility compared to the groups fed the processed seed meal. This could be due to the effect of residual antinutritional factors present in the processed seed meals. Emiola et al. (2013) reported adverse effects of residual anti-nutritional factors in mucuna seed meal on the performance of broiler chickens.
The nutrient digestibility (Table 6) of broiler chickens fed fermented seed meal based diet was significantly (P<0.05) better followed by those of broiler chickens fed boiled seed meal based diet and compared to those of broiler chickens fed raw, soaked and sprouted seed meals. This finding is in line with the report of Tuleun et al. (2011), who have reported that boiling and fermentation are more effective in neutralising of anti-nutritional components of the seeds. Osman (2007) further pointed out that the solubilisation of tannins occurred during fermentation resulting in a more significant decrease in the tannin content.

Conclusion
This study revealed that broiler chickens fed the processed Senna obtusifolia seed meal performed better than those fed the raw seed meal. Among the broiler chickens fed the differently processed seed meals, those fed the fermented Senna obtusifolia seed meal indicated the superior performance in terms of nutrient digestibility and growth performance. Up to 20% of fermented Senna obtusifolia can be incorporated in broiler diets with acceptable depreciation in biological performance. A further study should be conducted using raw or processed Senna obtusifolia to feed other monogastric animal such as rabbits, pigs and rats.