Commercial Feed Diluted with Different Fiber Sources and Enzyme Product for Broilers: Growth Performance, Carcass and Gut Health

ABSTRACT The dilution of commercial broiler feed with copra meal (CM), palm kernel meal (PKM) and cassava leaf meal (CLM) and enzyme supplementation was investigated. Two hundred and eighty 7-day old Cobb 500 broilers were fed commercial feed alone or diluted with the test ingredients with and without enzyme. There were no interaction effects (p>0.05) on feed intake (FI) and weight gain (WG). Poorer (p<0.05) feed conversion ratio (FCR) was observed on the diet diluted diets from 22-42 d, but this was restored (p>0.05) by enzyme supplementation. There was no interaction effect on final body weight (FBW). Diet dilution depressed FBW (p<0.05) but enzyme supplementation restored (p>0.05) this weight depression. Abdominal fat was lighter (p<0.05) on CLM compared to CM. There were no interaction effects (p>0.05) on the weight of gut segments and E. coli count. Heavier (p<0.05) liver, gizzard and intestine were observed on the test diets. Commercial feed dilution with CM, CLM and PKM at 100 g/kg for starter and 200 g/kg for finisher would be a viable option for smallholder broiler production. More research is needed into dilution levels and enzyme concentrations.


INTRODUCTION
Globally, poultry meat consumption is increasing at a faster rate in developing countries (Ravindran, 2012;OECD, 2018) where feed availability is a major production constraint (Ravindran, 2012).High feed cost due to unavailability of conventional ingredients such as maize and soybean meal, is the single most important factor affecting poultry production.Copra meal (CM), palm kernel meal (PKM) and cassava leaf meal (CLM) are moderate sources of protein but high in fiber and low in essential amino acids.There are reports of feeding CM, PKM and cassava leaf meal (CLM) (Eruvbetine et al., 2003;Sundu et al., 2006;Abdollahi et al., 2016;Devi & Diarra, 2017) to poultry but recommendations are generally low.There is the need for research in feed technologies to optimize the inclusion of CM, PKM and CLM in poultry diets.Dilution of commercial feed with CM at 200 g/kg significantly reduced cost without compromising performance of Hubbard broilers grown to 53 days (Pandi, 2005).However, report on feed dilution in modern broilers with higher nutrient requirements is still scanty.Recently, Mael et al. (2020) observed that the dilution of commercial feed at 100 g/ kg maintained performance and reduced the cost of producing Cobb 500 broilers, but at 200 g/kg dilution, enzyme supplementation was required.Diarra & Anand (2020) also found that both CM and CLM have potential to dilute commercial broiler feed with cost benefit.Although PKM is similar to CM and CLM in nutritional characteristics there are no reports on its use in commercial feed dilution for broilers.
Several enzyme products have been found to improve the utilization of fibrous ingredients by poultry and reduce feed cost ( Berwanger et al., 2017;Alagawany et al., 2018;Dayal et al., 2018;Rehman et al., 2018).Dietary fiber may also improve bird performance through enhanced gut health (Iji et al., 2001;Jha et al., 2019).
This study evaluated the performance of Cobb500 broilers fed commercial feed alone or diluted with CM, PKM and CLM.The hypotheses were (i) feed dilution will not affect bird performance, (ii) enzyme supplementation of the diluted feed will be beneficial, and (iii) birds fed the diluted feeds will have lower E. coli count compared to the control.

MATERIALS AND METHODS
The study was conducted at the Teaching and Research Farm of the Agriculture and Food Technology Discipline of the University of the South Pacific.The Animal Ethics Committee of the University approved the experimental protocol.

Experimental ingredients and diets
Expeller extracted CM and PKM, major by-products of coconut and palm oils extraction were obtained from Pacific Oil Samoa and Guadalcanal Plains Palm Oil Limited Solomon Islands, respectively.Cassava leaf harvested from 8-month-old sweet cultivar was sun-dried for 5 days and ground in a hammer mill from Golden Machinery Equipment Co. Limited (Zhengzhou Runxiang, China) to pass through a 4 mm sieve.The composition of the test ingredients in selected constituents is presented in Table 1.The test ingredients could not be analyzed for amino acid composition due to lack of analytical facilities in the study area and difficulties to send samples overseas during the lockdown to Covid-19.A commercial broiler feed based on wheat, maize and soybean meal from the Pacific Feed, Fiji served as the control.The crude protein and metabolizable energy contents of the control feed were 205 and 190 g/kg; 12 and 12.5 MJ/kg in the starter and finisher, respectively.The control feed supplied 12 and 5 g; 10.4 and 4.3 g of lysine and methionine/kg in the starter and finisher, respectively.The control feed contained 40 g crude fiber/kg in both the starter and finisher.

Experimental birds and management
Two hundred and eighty 7 d-old Cobb 500 male broiler chicks (185 ± 5.3 g) were allotted in groups of 10 to 28 open-sided floor pens (2.59 m 2 ) in a factorial arrangement (4 fiber sources x 2 enzyme levels).Each diet was fed to four replicate pens in a completely randomized design.The starter diet was fed from 8-21 d and the finisher from 22-42 d.Feed and drinking water were available ad libitum throughout the experimental period.The birds received 24 h light up to 14 d, and 15 h thereafter until the end of the experiment.

Data collection
Data were collected on feed intake, BWG, FCR, carcass and gut measurements and E. coli count.Feed intake was calculated by difference between the quantities supplied and left over.The birds were individually weighed at the start of the experiment, d 21 and d 42 and weight gain during each growth phase calculated by difference.Feed conversion ratio was derived as the ratio of feed consumed to weight gain and corrected for mortality.
On d 42, two birds weighing closer to the pen mean were fasted overnight for carcass studies and gut measurements.The birds were killed by cervical dislocation, scalded at 50 ºC for 30 seconds, manually plucked and eviscerated.Carcasses and different cuts were weighed and expressed as percentages of the liveweight.Gut segments (proventriculus, gizzard, intestine, caeca and liver) were also weighed on a portable digital scale (JadeverJKH-500 series, Smartfox, Auckland, New Zealand) sensitive at 0.1 g and expressed as relative to the live weight.Small intestine length was taken, from the duodenum to the ileocaecal joint, using a measuring tape and expressed as cm/kg body weight.The caeca were placed in labelled sterile sample bottles with ice and sent immediately to the microbiology laboratory for E. coli count following the procedure described by Wang et al. (2017).

Chemical analysis
The fiber sources were analysed for dry matter, nitrogen, total fat, crude fiber and ash according to standard procedures (AOAC, 1995).Crude protein (CP) was calculated as nitrogen × 6.25 (feed factor).

Statistical analysis
Data collected were subjected to one-way analysis of variance (ANOVA) (Steel et al., 1997)

Growth performance
The growth performance results are presented in Table 3.With the exception of FCR during the finisher phase, there were no interaction effects (p>0.05) on the growth parameters observed.The best F/G  (p<0.05) was recorded on the control.Enzyme supplementation of the CM and CLM-based diets improved (p<0.05) FCR comparable to the control but enzyme supplementation of the PKM diet had no effect (p>0.5) on FCR.
In the main effects, birds fed the control gained more (p<0.05)weight than those fed the CLM-diluted diet during the starter phase.Weight gain was not different (p>0.05) between the control, CM and PKM as well as among the test diets.During the finisher phase, the best FCR (p<0.05) was recorded on the control.Feed conversion ratio gain did not differ (p>0.05)among the test diets.Enzyme supplementation improved (p<0.05) F/G.Final body weight was heavier (p<0.05) on the control compared to CLM and PKM.Final body weight did not differ (p>0.05) between the control and CM and among the test diets.Enzyme supplementation improved (p<0.05) FBW.

Carcass measurements
Results of carcass measurements (Table 4) showed no interaction effects (p>0.05) on any of the parameters studied.Similarly, there were no main effects (p>0.05) on the relative weights of carcass, breast, thigh and drumstick.Birds fed the CLM dilution diet had lighter (p<0.05)abdominal fat than the control group.There was no difference (p>0.05) in abdominal fat weight between the control, CM and PKM diets.Enzyme supplementation did not affect (p>0.05)carcass measurements.

Gut measurements and E. coli count
Results of organ measurements and E. coli count are presented in Table 5.There were no interaction effects (p>0.05) on the relative weight of gut segments/ glands (liver, gizzard, proventriculus, caeca and intestine), intestine length and E. coli count.In the main effects, lighter (p<0.05)liver and gizzard were recorded on the control compared to the test diets.The weight of intestine increased (p<0.05) on CLM and PKM compared to the control.Intestine weight did not differ (p>0.05) between the control and Cm and among the test diets.Enzyme supplementation had no marked (p>0.05)effects on gut segments measured and E. coli count.

Growth performance
Currently, there are very few studies on dilution of commercial feed with fiber sources on broiler performance.The growth performance pattern observed suggests that this level of dilution (100 and 200 g/kg in the starter and finisher, respectively) can maintain broiler performance.Enzyme supplementation of the diluted diets was shown to be beneficial probably due to increased fiber hydrolysis.The beneficial effect of enzymes products on transit time in broilers fed fibrous CM (Diarra, S. S. et al., 2015;Devi & Diarra, 2017), rye (Lázaro et al., 2003), soybean (Adeyemi et al., 2013) and de-oiled rice bran (Anuradha & Roy, 2015) diets has been reported.Similar studies on commercial diet dilution with CM (Mael et al., 2020) and CM or CLM (Diarra, S. & Anand, 2020) also reported improvement in broilers with enzyme supplementation.The pattern of WG and F/G in the main effects was not clear but this suggests the need for more studies on enzyme concentration.

Carcass measurements
There were no interaction effects on the relative weights of carcass and cuts (breast muscle, thigh, drumstick and abdominal fat).The reason for reduced abdominal fat on CLM in the main effects was not clear but probably due to compositional differences among the fiber sources, especially in micronutrients.In the present study, the fiber sources were not analyzed for micronutrients but cassava leaf is known for its good profile in lysine (Morgan & Choct, 2016).Several studies (Ojano-Dirain & Waldroup, 2002;Adeyemi et al., 2013;Fouad & El-Senousey, 2014;Mendes et al., 2014) have confirmed the role of dietary lysine in reducing abdominal fat in broilers.Although all diluted diets were supplemented with lysine and methionine, possible beneficial effect of additional lysine from CLM may be postulated.The mode of action of dietary lysine on abdominal fat has mainly been attributed to its lipogenesis inhibitory activity (Fouad & El-Senousey, 2014).

Organ weight and E. coli count
The heavier liver and gizzard on the test diets is suggestive of increased activities of these segments on the test diets.Increased gizzard weight on high-fiber diets due to fiber accumulation and grinding activity in this organ is well reported (Hetland et al., 2004;Jiménez-Moreno et al., 2009).Increased biliary secretion for digestion and release of nutrients sequestered in the fiber fraction may also be implicated in the pattern of liver weight.Diarra & Anand (2020) also observed similar trends in gizzard and liver weights of broilers fed commercial diet diluted with CM or CLM.The pattern of full intestine weight in this study may be attributed to digesta weight on the test diets at the time of slaughter due to slower transit.The effect of dietary fiber on digesta transit time is well documented (Jiménez-Moreno et al., 2009;Rougière & Carré, 2010;Mateos et al., 2012).

Table 1 -
Composition of the experimental fibre sources.
of the GLM in SPSS (SPSS for Windows 2013, version 22.0; IBM Corporation, Armonk, NY, USA) with pen as the experimental unit.Treatment means were compared using the Duncan Multiple Range test and differences considered significant at p<0.05.

Table 2 -
Composition of the basal diets (as fed basis) and calculated analyses based on the nutrient content of the commercial feed, CM, CLM and PKM.

Table 3 -
Growth performance of broilers fed commercial diet alone or diluted with different fibre sources and enzyme supplementation.

Table 4 -
Relative weight of carcass and cuts (percentage) of broilers fed commercial diet alone or diluted with different fibre sources and enzyme supplementation.Values are means of 4 replications (n = 4); means in the column bearing different letters (a, b) are different (p<0.05),CM: copra meal, CLM: cassava leaf meal, PKM: palm kernel cake, ME: Metabolisable energy; SEM: standard error of the mean.

Table 5 -
Relative weight of gut segments (percentage), intestine length ((cm/kg weight)) and caeca E. coli count (log10 CFU/g) of broilers fed commercial diet alone or diluted with different fibre sources and enzyme supplementation.Values are means of 4 replications (n = 4); means in the column bearing different letters (a, b) are different (p<0.05),CM: copra meal, CLM: cassava leaf meal, PKM: palm kernel cake, ME: Metabolisable energy; SEM: standard error of the mean. eRBCA-2021-1546