The objective of this
study was to evaluate the impact of a low metabolizable energy (low-ME) diet
supplemented with a multienzyme blend
(KEMZYME®) on the growth performance, carcass
traits and meat quality of chickens. A total of 108 broiler chicks (Ross 308)
were randomly allocated to three experimental groups with six replicates per
treatment and five birds per replicate; the groups were treated as follows: a control diet with no additive
and standard metabolizable energy (ME; 3200 kcal kg-1); a low metabolizable energy (low-ME; 3000 kcal kg-1) diet;
and a low-ME diet + 0.5 g kg-1 diet of enzyme (low-ME–Enz). Live
body weight (LBW) at 43 and 47 d and body weight gain (BWG) during the periods from
38 to 43, 43 to 47 and 33 to 47 d decreased with the low-ME and low-ME–Enz diets in
comparison with the control-diet (p<0.05). The values of the feed
conversion ratio (FCR) were significantly increased with low-ME diets with or
without enzyme at all growing stages. There were no significant differences
among treatments in terms of carcass traits. With the exception of the jejunum
weight, dietary treatments did not affect any digestive tract segments. Meat
hardness decreased with the low-ME–Enz diet compared with the other diets (P=0.039). Meat yellowness of the breast muscle increased (P=0.001) with the
low-ME–Enz diet in comparison with the other treatments at 24 h
post-slaughter. In conclusion, the low-ME diet supplemented with
KEMZYME® did not influence most of
performance parameters and carcass traits of chickens; however, adding
enzymes to the low-ME diet is an effective strategy to improve the meat quality
criteria and small intestine characteristics.
Introduction
Maize (Zea mays) and soybean (Glycine max) meal (SBM) are major feedstuffs that
provide energy and protein in commercial poultry diets (Zanella et al.,
1990; Maisonnier-Grenier et al., 2004; Laudadio and Tufarelli, 2010),
as both ingredients are considered to be highly digestible. The
level of metabolizable energy (ME) of diets based on maize–SBM depends on
the digestibility of nonstarch polysaccharides (NSP), starch and protein.
Starch is the main source of energy in maize; however, complete digestion of
maize starch in the digestive tract does not occur as some
components are resistant to digestion (Brown, 1996; Tufarelli et al., 2007).
Nevertheless, nondigestible SBM carbohydrates can be available to broiler chickens in
presence of certain enzymes (Cowan, 1993). Therefore, enzyme-based
strategies have been used to enhance the nutritional benefit of maize and
SBM (Zanella et al., 1999; Maisonnier-Grenier et al., 2004).
Dietary supplementation with commercial enzymes as feed additives in
poultry, to enhance the productive performance, is a well established
feeding strategy (Alagawany and Attia, 2015; Abd El-Hack et al., 2017, 2018;
Alagawany et al., 2017, 2018b). Zanella et al. (1999) found that adding a
commercial enzyme to broiler chicken diets based on maize and SBM improved nutrient
availability, digestibility and broiler performance. In addition,
supplementation with enzyme enabled a reduced-energy diet to be adopted. On
the contrary, other studies have reported that supplementing enzymes in the
maize–SBM diet does not affect broiler chicken performance (Marsman et
al., 1997; Kocher et al., 2002; Meng and Slominski, 2005; Alagawany et al.,
2018a). KEMZYME® is a multiple-enzyme product containing multiproteases,
multiamylases and nonstarch polysaccharide (NSP) hydrolyzing enzymes,
which has been specifically developed to improve nutrient availability and
release extra amino acids and energy in multisubstrate broiler rations such
as maize–SBM and wheat–SBM. Naqvi and Nadeem (2004)
researched energy bioavailability of broiler diets using three levels of ME
(3200, 3000 or 2800 kcal kg-1) after supplementation with KEMZYME®. However,
little is known about the effect of commercial enzyme supplementation on
meat quality and digestive organs, as well as on the sections of the
digestive tract of broilers fed low-ME or normal-ME diets. Thus, the main
objective of this study was to assess the effect of low- and normal-ME level
maize–soybean-based diets supplemented with KEMZYME® on the growth performance,
meat quality, carcass traits and relative organ weights of broiler
chickens.
Ingredients and composition of diets fed to broiler chickens. (Min.–vit. premix refers to “mineral–vitamin premix”.)
Material and methodsBird management and treatments
The experimental procedures were approved by the Local Animal Care and
Ethics Committee of King Saud University, Riyadh, Saudi Arabia, ensuring
compliance with EC Directive 86/609/EEC for animal trials.
A total of 108 broiler chicks (Ross 308) were randomly allocated to three
treatments. Each group was divided into six replicates with six birds per
replicate. The experiment was carried out in an environmentally controlled
poultry unit within a temperature range of 22–24 ∘C. Broiler chicks
were raised in floor pens (1 m ×1 m) under similar management and
hygienic conditions. Standard finisher diets (32–48 d) with an
isonitrogenous content were offered in the form of maize–SBM mash (Table 1), and formulated
to meet or exceed the nutrient requirements of birds (NRC, 1994). Additional
enzyme supplementation was not included in the nutrient matrix (control
diet). KEMZYME® Plus is a multienzyme that combines three
different NSP enzymes (cellulase, β-glucanase and xylanase) for the
degradation of structural NSP, and two different endogenous-like enzymes
(protease and amylase), to enhance the action of endogenous enzymes secreted
in the gastrointestinal tract. KEMZYME® Plus is a feed enzyme
for piglets and poultry and improves the performance of animals when used as a
supplement. Reformulation with KEMZYME® Plus nutritional
matrix minimizes feed costs by enabling less expensive feeds that have a
higher fiber content and lower nutritional value to be used, when compared
with more expensive feeds.
Upon arrival, the chicks received starter feed from 1 to 21 d, and then grower
feed for the period from 22 to 31 d. Broilers were then distributed into the
following treatments: a control diet with no additive and standard
metabolizable energy (ME; 3200 kcal kg-1); a low metabolizable energy
(low-ME; 3000 kcal kg-1) diet; and a low-ME
diet + 0.5 g kg-1 diet of enzyme (low-ME–Enz).
Performance and carcass measurements
Feed intake was calculated on a daily basis by subtracting the amount of
feed rejected from the feed offered. Body weight was measured every 5 d, and the feed conversion ratio (FCR) was computed for each group. At 48 d, a total of 12 birds from each treatment were randomly selected and processed
to determine processing meat and carcass yields. Birds were put off feed for
10 h, then weighed and slaughtered, before being scalded and defeathered in
a rotary picker. Heads and shanks were removed, and the remaining carcass was
dissected to separate breast and leg. Similarly, fat, liver, intestines
(duodenum, jejunum, ileum and ceca), heart, spleen, thigh and drumstick
were separated and weighed. The percentage yield of each part was
calculated on the basis of dressing weight (Poorghasemi et al., 2013).
Effects of dietary treatments on the growth performance of broiler
chickens.
Treatments ItemsControlLow-MELow-ME–EnzSEMp valueLive body weight (BW; in grams)Day 331728173517204.070.326Day 3822562232220910.280.177Day 432662a2593b2577b13.420.012Day 473116a2993b2980b21.970.010Body weight gain (BWG; in grams)Day 33–38105.6599.3597.761.650.118Day 38–43101.38a90.08b91.91b1.610.003Day 43–4790.88a80.01b80.73b1.930.026Overall mean99.14a89.76b92.92b1.530.008Daily feed intake (in grams)Day 33–381791741802.310.508Day 38–431691701661.240.400Day 43–471741711691.850.511Overall mean1741721721.430.706Feed conversion ratio (FCR; grams per gram)Day 33–381.70b1.75a1.85a0.020.034Day 38–431.67b1.89a1.81a0.02<0.001Day 43–471.93b2.14a2.09a0.030.010Overall mean1.89b2.05a2.04a0.02<0.001
Different superscripts within rows represent significant differences (p<0.05); SEM represents the standard error of the mean; overall treatment p value.
Meat quality
The breasts were anatomized, and both pectoralis muscles were weighed. The
initial (at slaughter) and ultimate (after 24 h) hydrogen ion concentrations
(pHi and pHu, respectively) and the initial and ultimate color
component values (colori and coloru, respectively) were
determined. The pH was recorded using a pH meter (Model pH 211; Hanna
Instruments, Woonsocket, RI, USA). Two readings were obtained for the breast
muscle of each carcass, and the mean value of these measurements was the calculated. The
color components of the CIELAB color system (1976) – L* (lightness),
a* (redness) and b* (yellowness) – were measured using a
Chroma meter (Konica Minolta CR-400; Konica Minolta, Tokyo, Japan) and were
taken at two different locations on the top side of the breast muscle. An
average of the two readings of the color components was used for statistical
analyses. Following the measurements of pH and color quality, the breast
muscles were stored frozen at -20∘C for subsequent determination
of cooking loss (CL) and shear force (SF). The water holding capacity (WHC) of
the meat was measured according to the method described by Sun and Luo (1993).
The frozen samples were then thawed overnight at 4 ∘C, placed in a
commercial countertop grill (Kalorik GR 28215; Kalorik, Miami Gardens, FL,
USA), and cooked to an internal temperature of 70 ∘C. The
temperature was measured by introducing a thermocouple thermometer probe
(Ecoscan Temp JKT; Eutech Instruments, Singapore) into the central core of
the muscle. Muscles were weighed before and after cooking using a digital
scale (Mettler MP1210; Mettler-Toledo Ltd., Leicester, UK) to determine
the percentage CL as the difference between the initial and final weights.
The cooked samples used for determining CL were reused to obtain SF
according to Wheeler et al. (2005). Samples were cooled to room temperature
(22 ∘C), then cut into five 2.0 cm × 1.0 cm × 1.0 cm pieces, according to the methodology of Froning and Uijttenboogaart (1988). Shear force was determined as the maximum force (in kilograms) perpendicular
to the fiber using a texture analyzer (TA.HD Stable Micro Systems; Stable
Micro Systems Ltd., Godalming, UK) attached to a Warner–Bratzler knife.
The crosshead speed was set at 120 mm min-1.
Statistical analysis
Data were subjected to an ANOVA using the general linear model (GLM) procedure in SPSS (SPSS, 1997). The differences between means were determined using
the ANOVA procedure, followed by a Tukey post-hoc test to separate means.
A p value of 0.05 was used to assess significance among means.
Results and discussion Growth performance
The effect of the dietary treatments on the broiler performance are reported
in Table 2. Live body weight (LBW) at 43 and 47 d and body weight gain
(BWG) during the periods from 38 to 43, 43 to 47 and 33 to 47 d decreased with low-ME and
low-ME–Enz diets in comparison with the control (p<0.05). The
values of the feed conversion ratio (FCR) were significantly increased with
low-ME diets with or without enzyme, for all ages. There were no significant
differences between the three treatments in terms of daily feed intake. The
current study demonstrated that supplementation of enzyme in a low-ME diet had
no major effect on any performance parameter. A reason for this may be that the
study lasted only 16 d. Naqvi and Nadeem (2004) found that chickens fed
the intermediate-level energy (3000 kcal kg-1) diet plus KEMZYME® achieved
better BWG and FCR values in comparison with those fed the same level of ME without
KEMZYME® supplementation; however, the BWG and FCR values were comparable to animals that were fed on the
control diet (3200 ME kcal kg-1). Perić et al. (2008) investigated the
effect of supplementation of an enzyme complex (containing amylase,
protease, xylanase, β-glucanase, cellulose, pectinase and phytase)
in broiler chicken diets on growth performance, and they found that enzyme
supplementation had a positive effect on BWG and FCR. Zhou et al. (2009)
found that the supplementation of broiler chicken diets with enzyme improved the utilization
of ME, particularly in rations with lower ME levels. On the contrary, other
researchers did not find any positive effects of dietary supplementation of
enzyme for broiler chickens. Günal et al. (2004) found that the dietary
supplementation of enzyme had no effect on BWG, dry matter intake, feed
intake or the FCR of chickens. Similar results have been found in other
studies. Live body weight, feed efficiency, feed intake and survivability
of chickens were not significantly affected by dietary supplementation of
enzyme (Sayyazadeh et al., 2006). Sherif (2009a) observed positive effects
of some enzyme preparations (Natuzyme and Sicozyme) added to diets on the
final LBW and BWG of broilers during the grower–finisher stage, but feed
intake and FCR were unaffected. In another study, Sherif (2009b) reported
that the addition of Avian Plus and Natuzyme enhanced the FCR and economic
feasibility of broiler chickens fed plant protein sources, but feed intake
and BWG were not influenced. Moreover, Cho et al. (2012) reported that
feeding broilers with low-ME diets decreased the growth rate, and that these
effects were alleviated by dietary supplementation of emulsifiers to the
extent that growth was similar to that of birds fed high-ME diets.
Effects of treatments on carcass yield and proportions of various
carcass parts and organs (n=6).
Different superscripts within rows represent significant differences (p<0.05); SW represents slaughter weight.
Carcass traits and relative organ weights
Our findings indicated that there were no significant differences among the
treatments in terms of carcass traits (Table 3). However, spleen weight and
carcass yield were improved with the low-ME diets, either with or without
enzyme, in comparison with the control. These results are in agreement with
those of Holsheimer and Ruesink (1993), who found that carcass yields were
not affected by gradual increases of ME (from 2750 to 3250 kcal kg-1 diet).
Downs et al. (2006) reported similar results; they observed that dietary energy
density did not influence carcass characteristics of broiler chicks. On the
contrary, Mohammadigheisar et al. (2018) found that chickens fed a low-energy diet with multienzyme supplementation had the highest relative liver
weights (p<0.05). Hidalgo et al. (2004) reported similar responses
of carcass yield to increasing levels of ME in the rations of straight-run
broilers. Sayyazadeh et al. (2006) concluded that abdominal fat and carcass
yield of broiler chickens were not significantly influenced by
supplementation of enzyme to wheat, maize and barley-based diets. Conversely, Bin Baraik (2010) found no effect of commercial enzymes, applied
individually or in combinations, on carcass yield, dressing percent and
weight of internal organs of broilers. They also observed that there were no
statistical differences in the percentage of commercial cuts (drumstick, breast,
wing and thigh). These results also agreed with the recent results obtained
by Younis (2013).
Effects of dietary treatment on the meat quality of broiler chickens.
Treatments ItemControlLow-MELow-ME–EnzSEM1p value2Water holding capacity (%)21.620.320.30.2600.089Myofibril fragmentation index0.4580.4580.4240.0010.256Cooking loss (%)35.0836.5433.890.6030.203Shear force (kg)1.651.631.240.1180.287Hardness (kg)0.68a0.68a0.54b0.0200.039Springiness index0.700.690.720.0010.310Cohesiveness index0.470.470.490.0070.484Chewiness index0.230.220.190.0090.209
Different superscripts within rows represent significant differences (p<0.05).
Effects of dietary treatments on the color and pH of broiler
chicken meat.
Treatment ParametersControlLow-MELow-ME–EnzSEM1p value2pHi (initial value at slaughter)6.516.456.650.0330.108pHu (ultimate value after 24 h)5.99b5.98b6.08a0.010.032Temperature (∘C, at slaughter)26.58a25.51b22.55c0.35<0.001Colori (initial value at slaughter)L*39.0139.8740.180.550.687a*2.142.252.580.1040.214b*2.512.983.370.170.130Coloru (ultimate value after 24 h)L*45.3744.5045.710.4110.473a*2.692.532.660.150.914b*4.11b4.30b5.84a0.220.001
Different superscripts within rows represent significant differences (p<0.05); L*: lightness; a*: redness; b*: yellowness.
Intestinal segments
Dietary treatments did not affect digestive tract segments, apart from
jejunum weight. Jejunum weight decreased under a low-ME or low-ME–Enz diet,
when compared with the control (Table 3, p<0.001). To adapt to
those changes, secretion activities of the intestine may increase, which, in
turn, may lead to increases in the weight and size of the gastrointestinal
tract, liver and pancreas. Increased size of the gastrointestinal tract and
intestine could be adaptive responses to an increased need for exogenous
enzymes (Brenes et al., 1993). On the contrary, Wang et al. (2005) showed
that the length and weight of the ileum and the length of the cecum
decreased (linearly, p<0.01) at 21 d of age with increasing
dietary enzyme supplementation. Additionally, the length and weight of the
ileum and the length of cecum decreased (linearly, p<0.05) as the
enzyme level increased at 42 d of age. Moreover, at the ages of 21 and 42 d, relative weights of liver and pancreas decreased (linearly, p<0.01) with increasing enzyme level (Wang et al., 2005). Brenes et
al. (1993) stated that the addition of supplemental enzymes to barley-based
diets reduced the lengths of the jejunum, duodenum and ileum, but enzyme
treatment had no significant effect on organ size in a wheat-based diet. In
general, the use of commercial enzymes in the control diet or in the low-ME
diet altered the morphology of the different segments of the gastrointestinal
tract when compared with the control diet. Enzyme addition to broiler diets
resulted in positive impacts on the energy digestibility of broilers (Pourreza et
al., 2007). Xylanase supplementation significantly improved nutrient
utilization and more nutrients were available to the poultry (Hosseini and
Afshar, 2017; Tufarelli et al., 2007). Ramesh and Chandrasekaran (2011)
reported that supplementation of enzyme improved the apparent metabolizable
energy, and protein and NSP digestibilities in birds, which helped with better
utilization of feedstuffs.
Meat quality criteria
Apart from meat hardness, no parameters of meat quality were statistically
different among the treatments (Table 4). Hardness was lower with the
low-ME–Enz diet when compared with the control and low-ME diets (P=0.039).
In agreement with our results, Habib (2016) reported that the physical
properties of broiler breast meat (pH and water holding capacity) were not
significantly affected by enzyme supplementation (P>0.05). These
results were also in agreement with the data obtained by Bin Baraik (2010),
who observed no significant effect of commercial enzymes (xylanase and
phytase), applied individually or in combination, on meat composition and
meat quality values.
The results of the present study showed that the yellowness of breast muscle
was increased (P=0.001) with the low-ME–Enz diet in comparison with the
other treatments 24 h after slaughter. Lightness and redness were not
influenced by dietary treatment, which is inconsistent with the data of Cho
and Kim (2013) and Mohammadigheisar et al. (2018), who showed that feeding
broiler chickens on low-energy diets resulted in a higher lightness value. On the contrary, the supplementation of multienzymes to low-energy diets decreased the lightness value. The results presented in Table 5
show that, 24 h after slaughter, the pH of the breast meat was affected
(p=0.032) by treatments, and the low-ME–Enz diet had a higher pH (6.08). At
slaughter, the pH value was not influenced by dietary treatments. However, the
results of the current study contradict the findings of Wang et al. (2009),
who found that dietary treatments had no effect on the pH of breast meat.
The temperature at slaughter was significantly decreased with treatments
when compared with the control (p<0.001).
Conclusions
Our data showed that a low-ME diet supplemented with KEMZYME® did not affect
most performance parameters and carcass traits of broiler chickens. However,
live body weight at 43 and 47 d and body weight gain during the periods from 38 to 43,
43 to 47 and 33–47 d were significantly decreased with the low-ME and
low-ME–Enz diets in comparison with the control. The values of the feed
conversion ratio were significantly increased with low-energy diets with or
without enzyme for all ages. Thus, adding enzymes to low-energy diets is an
effective feeding strategy to improve the meat quality criteria and small
intestine characteristics.
Data availability
The data sets are available upon request from the corresponding
author.
Author contributions
EOSH and GMS performed the research and collected data. AMA, ANA and AAS developed the research topic. SHA, MEAE and MA provided valuable statistical
expertise. AT and VL provided useful expertise on meat quality. VT wrote and
edited the paper with support from MEAE and MA.
Competing interests
The authors declare that they have no conflict of interest.
Acknowledgements
The authors thank their respective departments for support.
Review statement
This paper was edited by Manfred Mielenz and reviewed by two anonymous referees.
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