Enzyme Supplemented Neem Leaf Meal Based Diets: Effects on Carcass and Meat Quality of Broiler Chickens

— The study investigated the influence of neem leaf meal (NLM) with or without enzyme supplementation on carcass and meat qualities of broiler chickens. Two hundred and eighty eight (288) broiler chickens were randomly allocated to diets in which NLM was included at 0, 1.5, 3 and 5% with and without enzyme supplementation to form eight (8) dietary treatments. There were three (3) replicates per treatment and twelve (12) birds per replicate in a 4 x 2 factorial arrangement. At the end of the 8 th week, three chickens/ replicate were humanely slaughtered for assessment of carcass and organ characteristics and meat quality of the thigh, chest and drumstick muscles. The results showed that only the relative weights of back (g/kgLW) was significantly influenced (P<0.05) by levels of NLM inclusion. There was also significant (P<0.05) increase in relative weights (g/kgLW) of the liver and pancreas of the broilers with NLM inclusion. Cooking loss, thaw loss and palatability of meat from these chickens were not adversely affected by inclusion of NLM in the diets. Furthermore, the values obtained for moisture contents of the 3 muscles were within acceptable range. In conclusion, inclusion of NLM in broiler finishers ’ diets up to 5% did not jeopardize the development of carcass and organs, and meat quality of the chickens. Additional effect of enzyme supplementation was not observed in this study.


INTRODUCTION
The poultry industry has been a major supplier of affordable animal protein because chickens especially have a short generation interval, quick turnover, and fast growth rate (Allouche et al., 2015;Ubuaet al., 2019). However, highcost of conventional feedstuffs has been a major setback on the path of the industry in Nigeria (Sunmola, 2018). For instance, with the increase in production of maize and other feed stuffs, the price also keeps rising (FAO, 2013) and in order to ensure fast and optimum growth of broiler chickens, provision of a well-balanced ration is necessary.
The search for alternative feed ingredients like agroindustrial waste (Fabunmi et al., 2019), leaf meal and other unconventional feed stuffs (Hien et al., 2017) became necessary so as to cushion the effect of high cost of feed ingredients vis-à-vis high cost of poultry feed. However these alternative feed ingredients come with considerable amount of fibre and antinutrients (Akintomide et al., 2021) but might be better utilized with the inclusion of exogenous enzymes (Razaet al., 2009) to the diet.Polyzyme®, an exogenous enzyme,contains xylanase, phytase, cellulase, β -glucanase, pectinases, αamylase, protease, α -galactosidase, βgalactosidase, lipase and mannanase, which are able to digest complex carbohydrates. Polyzyme®is used at the manufacturer's recommended dosage of 400g per ton of mash feed (Sunmola et al., 2019).
Neem leaf contains a good amount of protein, minerals and vitamins although it is high in fibre which is characteristic of leaves (Ubua et al., 2019;Akintomide et al., 2021). Kumar et al.(2010) reported the relevance of neem leaf meal (NLM)to poultry due to itsanti-bacterial, anticoccidial, anti-oxidant and hepatoprotective properties. It Akintomide et al. International Journal of Environment,Agriculture and Biotechnology,7(1) could also serve as an antiprotozoal, antifungal and immune modulatory agent (Kale et al., 2003). Various inclusion levels has been suggested, Ubua et al. (2019) recommended the inclusion level of 2.5% NLM, Akintomide and Onibi (2018) reported that broilers were able to tolerate 5% NLM and oral administration of aqueous infusions of neem leaf up to 0.3% in drinking water was reported by Egbeyale et al.(2021)but there is a dearth of information on the inclusion of NLM on broiler meat quality. This study was therefore designed to investigate the effect of NLM with or without Polyzyme® supplementation on carcass and organ characteristics, and meat quality of broiler chicken.

Management Practices for Experimental Birds:
The NENT (2018)ethical guidelines for the use of animals in research were adopted. The experiment was also approved after due presentations to the research protocol team of the Department of Animal Production and Health, FUTA. Two hundred and eighty eight (288) broiler chicks (Marshall Breed) were purchased from a reputable hatchery and were randomly allocated to the 8 dietary treatments. Each treatment was replicated thrice with12 birds per replicate in a 4 x 2 factorial arrangement on a completely randomized design. Birds were raised under good hygienic conditions in deep litter throughout the experimental period which lasted for 8 weeks. Experimental diets and potable water was supplied ad libitum. Vaccines were administered as scheduled.
Carcass and Meat Quality Assessment:At the end of the8 th week,three birds per replicate were randomly selected and humanely slaughtered for carcass and meat quality assessment.
Carcass and organ measurements: Live weight was taken at point of slaughter. At the end of the bleeding process the body weight was determined. Subsequently the chickens were defeathered after scalding in hot water, dressed, eviscerated, dissected into parts and weighed. The following weights were taken; live, eviscerated, thigh, drumstick, neck, head, shank, wing, chest and back. The internal organs; liver, kidney, lungs, heart, gizzard, proventriculus, spleen and pancreas were also separated and weighed.
Cooking loss: Meat samples of thigh, chest and drumstick were initially weighed (before cooking) and carefully put into well labeled polythene bags. These bags were then cooked in boiling water for 35 minutes after which they were removed, drained and allowed to cool to room temperature. Each cooked meat sample was then reweighed (final weight) and cooking loss obtained as: Cooking loss (%) = Initial weight of meat -Final weight of meat / Initial weight of meat x 100 / 1.

Thaw loss:
Frozen samples of the three muscle types were removed from the freezer after about four weeks, weighed (initial weight), put into well labeled nylon (perforated) and placed in the fridge for 24 hours to thaw. The samples were then removed from the nylons, mopped and reweighed (final weight). Thaw loss (%) = Initial weight of meat -Final weight of meat / Initial weight of meat x 100 / 1.

Moisture content:
Moisture content of the three muscle types were determined. First, aluminum foil was weighed then meat sample was put into it and weighed again. The foil and content were placed into the oven at 70 o C for 72 hours after which they were cooled and reweighed. Moisture content (%) =Loss in weight of sample / Weight of sample before drying x 100 / 1.

Palatability:
The thigh muscle was used for palatability test after measurement of cooking loss. The samples were de -skinned, visible fat removed and cut into small pieces which were coded and evaluated by a 9 -member untrained student panel using a 9 point hedonic scale from extremely dislike (1) to extremely like (9).

Statistical Analysis
All data generated were subjected to one-way analysis of variance (ANOVA)and factorial analysis as appropriate. Where significant differences were found, means were compared using Tukey test of the Minitab Statistical Package Version 17.

Carcass and Organ Characteristics
Akintomide et al. The results of the organ weights (g/kg live weight) of broiler finishers fed diets containing NLM with or without Polyzyme® supplementation are presented in Table 2. The weights of liver, pancreas and proventriculus were significant (P<0.05) due to level of NLM fed to the broiler chickens. The relative weights of liver and pancreas followed same trend with 5% NLM having the highest values and control having the lowest values. Broilers fed 5% NLM also had the highest proventriculus weight. The relative weights of the liver, kidney, heart, lungs, gizzard, pancreas, proventriculus and spleen were not significantly (P>0.05) influenced by Polyzyme® supplementation.

IV. DISCUSSION
Slaughtered chickens are not only sold as whole but also in smaller cuts. Hence, effect of alternative feedstuffs on these cuts is worth considering. Furthermore, meat from the chest, thigh and drumstick are the most expensive commercial cuts from a chicken (Adeyemi et al., 2008). Neem leaf meal (NLM) did not affect the carcass yield as seen in the non-significant differences recorded for eviscerated weight in this study. All parts except the back were not influenced by levels of NLM inclusion. Bonsuet al. (2012) also reported a non-significant difference in dressed weight of broilers fed up to 2.5% NLM in their diets. In addition, the results of this study agree with that of Ubuaet al. (2019) in which no significance was observed in the carcass characteristics of broilers fed NLM. So, it can be safely inferred that the inclusion of up to 5% NLM promoted similar carcass development of the broilers as they utilized the NLM-based diets for muscle growth (Ubuaet al., 2019). Addition of Polyzyme® did not elicit any adverse effect on muscle development of the chickens. This is in line with the report of Sunmolaet al.
(2019) in which no significant difference was observed in the dressed, thigh and breast weights of broiler chickens fed sweet orange peel meal withPolyzyme® supplementation. It is noteworthy that responses to feed enzymes are variable and they depend on enzymes, substrate and individual birds so, there could be physiological limitations to the use of enzymes (Ravindran, 2013).
An increase in the relative weights of liver and pancreas was observed with increased NLM inclusion. Birds on the 5% NLM diets had the highest liver, pancreas and proventriculus weights. These three organs are highly involved in the digestion of feedstuffs. The proventriculus produces gastric juices and enzyme needed for digestion (PoultryHub, 2018), working closely with the gizzard. Svihus (2014) opined that the proventriculus and gizzard can be considered as one organ. The pancreas also produces the pancreatic juice to further aid digestion. In addition to bile production (PoultryHub, 2018), the liver helps to remove waste and toxins from the body system. So, increase in weights of these organs is suggestive of increased activities either due to the high fibre level of NLM or the phytochemicals it contains. According to Obunet al. (2013), there was no significant difference in liver and pancreas weights of broilers fed control and 5% NLM diets and a reduction (P<0.05) in gizzard weight was observed. Bonsuet al. (2012) also reported no significant difference in weights of liver and gizzard of broiler fed NLM up to 2.5%.
It can be seen from the results that levels of NLM up to 5% and Polyzyme® supplementation did not adversely affect the meat quality of these broiler chickens as depicted by the non-significance in cooking loss, thaw loss and palatability. Values for moisture content of thigh muscle though significant did not show any particular trend with inclusion of NLM. All values for moisture content were within the range of 66-75% described for meat by USDA (2011). According to Belle (1937), meat with cooking loss between 20-25% has excellent flavour and higher values of about 40-50% will leave the meat dry. High values of cooking loss will affect the eating quality of meat unfavourably (Mehmoodet al., 2019).Cooking loss values according to level of NLM in this study were between 18.93-28.22% and that of enzyme supplementation was between 20.15-26.95%. Since these values were not up to 40%, it could be safely inferred that the flavour and juiciness of meat from the broiler chickens were not adversely affected. The thaw loss across the 3 muscle types was less than 4% which in essence did not predispose the meat to high loss due to leaching of soluble protein and flavour. Contrary to Bonsuet al. (2012) that reported a slight bitter taste in meat of broilers fed up to 2.5% NLM, the palatability and general acceptability of meat in this study were not compromised.

V. CONCLUSION
It can be concluded that the inclusion of up to 5% neem leaf meal with or without Polyzme® supplementation did not jeopardize the carcass, organ and meat quality of broiler chickens. Moreover, there is the need for further research to justify the use of Polyzyme® in broiler diets with inclusion of neem leaf meal.