Tomato (Lycopersicon esculentum) is one of the most popular vegetables used as salad in food preparations and also commercially in form of juice, soup, puree, ketchup or paste. Commercial processing of tomato produces a large amount of waste at various stages.
The wet tomato pomace which amounts to 81,000 tons annually in Iran is considered
as waste and may cause serious environmental problems (Pirmohammadi
et al., 2006). Dried Tomato Pomace (DTP) is a mixture of tomato skin,
pulp and crushed seeds that remain after the processing of tomato for juice,
paste and/or ketchup. The proximate analysis shows that DTP may contain considerable
nutrients such as crude protein, crude fiber, ether extract and nitrogen free
extract (King and Zeidler, 2004). Elloitt
et al. (1981) demonstrated that DTP is a good source of protein and
the chemical composition of tomato cannery wastes suggests that this by-product
contains 20-25% protein with 13% lysine more than that of soybean meal protein
(Sogi et al., 2002), therefore has the potential
to be applied as a high protein ingredient in poultry diets (Persia
et al., 2003). The results of research studies show that the anti-nutritive
factors found in unheated tomato pomace do not induce any unfavorable impacts
on productive traits of broiler chicks as a result it can be used in broilers
diet to provide some parts of protein requirement (Persia
et al., 2003). The only limiting factor for its application in the
diet can be the presence of poisonous pesticides residue in the waxy skin layer
Tomato pulps can be incorporated up to 15% to the diet without indicating any
adverse effects on broilers performance and carcass yield (King
and Zeidler, 2004).
Dotas et al. (1999) showed that dried tomato
pulp can be used at 8% for laying hens and if diets are supplemented by fat
this amount can raise to 12% for broilers without any harmful influence on performance
parameters. DTP should not be used >20% of the whole diet for broiler chickens
because its high level of crude fiber limits the energy of the diet and also
the excessive powder removes the taste of the diet (Al-Betawi,
2005). In spite of existing research (Persia et
al., 2003; King and Zeidler, 2004; Al-Betawi,
2005; Jafari et al., 2006) that evaluated
the impact of DTP on performance of broilers and laying hens none were found
that have employed incremental levels of DTP in order to optimize the inclusion
rate of DTP in broiler diets. Thus, this study was designed to evaluate the
effect of incremental levels of DTP in combination with commercial enzymes on
growth performance and dietary ileal protein digestibility in broiler chickens.
MATERIALS AND METHODS
Dried Tomato Pomace (DTP) was purchased from a tomato processing company. The
nutrient analysis of DTP was carried out according to the standard methods of
analysis (AOAC, 1996) in order to determine dry matter,
crude protein, crude fat, crude fiber, ether extract, calcium and phosphorous
concentration (Table 1).
Animals and diets: A total number of 384 days old broiler chicks (Ross 308) were raised in one group till the 7 days of age. At day 7, chicks were divided into 32 groups of 12 birds each and every 4 groups were randomly allocated to one of 8 experimental diets according to a factorial arrangement based on a completely randomized design. Treatments included 0, 3, 6 and 9% of dried tomato pomace from 7-21 ddys; 0, 6, 9 and 12% from 21-42 days and 0, 9, 12 and 15% from 42-49 days with (A-D groups) and without (a-d groups) enzyme supplementation.
A commercial multi enzyme containing 10% visco units, 2200 IU xylenase, 200 IU β-glucanase and also cellulase, pectinase, protease and β-mono cidaze per gram was added to the enzyme supplemented diets at the concentration of 500 g ton-1. All the chicks were fed the same pre-starter diet from 1-7 days containing 20.6% crude protein and 2870 kcal metabolizable energy per kg of diet.
Experimental diets were formulated to be isocaloric and isonitrogenous in the
starter (7-21 days), grower (22-42 days) and finisher periods (43-49 days) to
meet the requirements according to NRC (1994) (Table
2). All diets were fed in mash form through out the 7 weeks experimental
period. Birds had free access to water and feed and were maintained under 23
h light program. The environmental temperature in the house was initially set
at 32°C and gradually reduced to 22°C by week 6.
Data collection and sampling: Body weight and feed intake were monitored at 7, 21, 42 and 49 days of age using pens as the experimental units. Before weighting, the birds were fasted for 4 h. At day 49, two birds per pen with a body weight close to the mean were individually weighed and slaughtered.
Then proportion of the carcass, abdominal fat, heart, liver, gizzard and small
intestine weight to live body weight were calculated. To determine ileal protein
digestibility of the diets, 3 g kg-1 chromic oxide were added to
the diets for 5 days at day 44 and at 49 days of age, two birds randomly selected
from each replicate were killed by cervical dislocation. Then, contents of the
ileum (from Meckels diverticulum to 1 cm above the ileo-caecal junction)
were collected. The ileal digesta samples were frozen, freeze dried, ground
and analyzed for nitrogen and chromic oxide to determine ileal protein digestibility
(Batal et al., 2000).
Chemical analysis: Feed and ileal digesta samples were analyzed for
chromic oxide using the procedure described by Fenton and
Fenton (1979). Nitrogen was determined by the Kjeldahl method and the protein
contents were calculated using the multiplication factor of 6.25. The following
equation was used for the calculation of ileal proten digestibility:
Litter moisture: At 49 days homogenous, 100 g L samples from each pen
were taken and dried in 105°C for 48 h and litter humidity was calculated,
Statistical analysis: The GLM procedure of SAS (SAS Inst. Inc., Cary,
NC) was used to analyze the continuous variables of the broiler chicken data.
Duncan (1995)s multiple range test was applied
to separate means. Statements of statistical significance are based on a probability
||Ingredients and compositions of the experimental diets in
|All enzyme supplemented diets had the same composition but
contained 0.05% ravobio multi enzyme; 1: mineral premix per kg of diet:
Fe (FeSO4.7H2O, 20.09% Fe), 50 mg; Mn (MnSO4.H2O,
32.49% Mn), 100 mg; Zn (ZnO, 80.35% Zn), 100 mg; Cu (CuSO4.5H2O),
10 mg; I (KI, 58% I), 1 mg; Se (NaSeO3, 45.56% Se), 0.2 mg; 2:
vitamin premix per kg of diet: vitamin A (retinol), 2.7 mg; vitamin D3 (cholecalciferol),
0.05 mg; vitamin E (tocopheryl acetate), 18 mg; vitamin k3, 2 mg; thiamine
1.8 mg; riboflavin, 6.6 mg; panthothenic acid, 10 mg; pyridoxine, 3 mg;
cyanocobalamin, 0.015 mg; niacin, 30 mg; biotin, 0.1 mg; folic acid, 1 mg;
choline chloride, 250 mg; antioxidant 100 mg
RESULTS AND DISCUSSION
Performance: Data obtained on performance parameters are shown in Table
3. Considering BWG there was no significant effect of treatments at 7-21
days but in other periods increasing dried tomato pomace markedly (p<0.05)
decreased BWG particularly in D treatment. This is while, no significant differences
were observed among DTP added groups. Enzyme supplementation marginally improved
BWG of broiler chicks, particularly over the 21-42 days period. The results
are in accord to those reported by Almirall et al.
(1995) who reported that B-glucanase enzyme improved body weight of broilers,
this enzyme decomposes glucanes and none starch polysaccharides and enhances
digestion and absorption of nutrients. But as dietary inclusion rate of DTP
increased (c and d groups) even enzyme supplementation could not compensate
for the weight reduction due to increasing DTP. Birds fed the control diet were
significantly heavier at 42 and 49 days of age compared to other treatments.
This could partially be due to the high fiber content of the diet and consequently
reduced energy access of the chicks. Persia et al.
(2003) also observed significant reduction in weight gain of broiler chickens
in the 8-21 days phase as the tomato waste level increased. Additionally, high
content of fiber allows exaggerated multiplication of intestinal bacteria which
may reach superior portions of jejunum producing acids which degrade enzymes
in charge of digestion. The chickens fed with enzyme-supplemented diets had
higher body weights in comparison with none supplemented diets, probably because
of the increasing digestibility of nutrients and more availability of energy
as a result of enzyme activity. Similar to current findings, Liral
et al. (2010) also reported a linear reduction of body weight in
different weeks of age as the inclusion rate of tomato wastes increased in broiler
The highest level of DTP inclusion resulted in a marked increase in feed intake
at 21-42 days compared to control birds. But enzyme inclusion in the diet reduced
feed intake compared to none-supplemented groups, although the differences observed
did not reach statistical significance. Feed intake increasing can be justified
with regards to diet high fiber which limits energy access also the NSPs in
contact with water form a gel that reduces passage time and absorption of nutrients
and thus, increases feed consumption to compensate and meet nutritional demands.
In treatments with enzyme, though no significant differences were found, the
feed intake reduced because of the effects of enzyme on non starch polysaccharides
and subsequent improvement in digestibility and absorption (Table
3). There was no impact of experimental diets on cumulative feed consumption
over the 42-49 days and entire period. This result may be related to ingestion
and digestion capacity which, increases as the birds get older, adult birds
seem to be able to fit to high fiber content diets as they have a better developed
digestive tracts compared to younger birds so that they can reduce or neutralize
negative effects of fibrous portion of the diet (Potter
et al., 1990; Philip et al., 1995).
||Effect of incremental levels of tomato pulp powder on body
weight, body weight gain, feed intake and Feed Conversion Ratio (FCR) of
broilers chickens at different ages
|a-c Means in a row with no common superscripts differ significantly
(p<0.05); 1A: control (0% tomato pulp powder in starter, grower
and finisher); B: 3, 6 and 9% tomato pulp powder in starter, grower and
finisher, respectively; C: 6, 9 and 12% tomato pulp powder in starter, grower
and finisher, respectively; D: 9, 12 and 15% tomato pulp powder in starter,
grower and finisher, respectively; a, b, c and d are enzyme supplemented
||Effect of incremental levels of tomato pulp powder on carcass
traits and lymphoid organ weights of broiler chickens (percentage of body
weight) at 49 days of age
|1A: control (0% tomato pulp powder in starter,
grower and finisher); B: 3, 6 and 9% tomato pulp powder in starter, grower
and finisher, respectively; C: 6, 9 and 12% tomato pulp powder in starter,
grower and finisher, respectively; D: 9, 12 and 15% tomato pulp powder in
starter, grower and finisher, respectively; a-d are enzyme supplemented
Feed efficiency deteriorated significantly as the inclusion level of DTP increased in different periods and birds receiving the control diets exhibited the lowest FCR (p<0.05). High fiber content of the diet and the limitation of diet energy or the presence of pesticides residue in the outer skin layer of tomato pulps may account in part for deterioration of FCR.
Enzyme supplementation also, none significantly improved feed efficiency and
marginally decreased FCR in different phases, the reduction was more pronounced
in b group. The current results are in line with those obtained by Alam
et al. (2003) who reported that by addition of enzymes the anti nutrient
effects of non starch polysaccharides are reduced and improvement of growth
performance is achieved.
Jafari et al. (2006) also observed decrease
of feed efficiency in laying hens at 27-38 weeks of age with the inclusion of
up to 15% of tomato waste in their diets. These findings are in agreement with
those reported by Buchanan et al. (2007) who
indicated that inclusion of 24% of DTP in broiler diets resulted in the worst
feed conversion ratio due to high fiber content. On the contrary in a study
with laying hens, Nobakht and Safamehr (2007) reported
that DTP did not have any adverse impact on final BW and FCR of hens when inclusion
rate increased to 7.5%.
Carcass traits: As Table 4 displays carcass characteristics
were not influenced by experimental diets. Broilers in enzyme supplemented groups
tended to have higher carcass yield and lower abdominal fat but the impact of
enzyme disappeared when the inclusion rate of DTP increased (c and d groups).
The obtained results are similar to that reported by King
and Zidler (2004) who showed that DTP up to 15% in diet does not affect
carcass traits of broiler chicks. Enzyme supplementation could have had a positive
effect on nutrient digestibility and energy availability resulting in higher
carcass yield compared to none supplemented groups.
Ileal protein digestibility and litter moisture: According to Table
5, there was no deleterious effect of DTP inclusion in diet detected on
protein digestibility at 49 days and the obtained values were quite similar
among dietary treatments. These results confirm the previous reports stating
that DTP is a high quality vegetable protein source and there are no anti-nutritional
factors in DTP which may influence protein digestibility (Liadakis
et al., 1995; Sogi et al., 2005). DTP
had no significant impact on litter moisture measured at 49 day of age. But
the moisture content of the litter marginally decreased by enzyme supplementation.
||Effect of incremental levels of tomato pulp powder on ileal
protein digestibility and litter moisture at 49 d of age
|1A: control (0% tomato pulp powder
in starter, grower and finisher); B: 3, 6 and 9% tomato pulp powder in starter,
grower and finisher, respectively; C: 6, 9 and 12% tomato pulp powder in
starter, grower and finisher, respectively; D: 9, 12 and 15% tomato pulp
powder in starter, grower and finisher, respectively. a-d are enzyme supplemented
Similar to the findings, Adams (2003) showed that enzyme
supplementation in broiler diets reduced litter moisture, probably because enzyme
activities decreases water binding capacity of NSPs which reduces wet droppings
and consequently litter moisture.
The ambivalent reports regarding the effectiveness and the optimum inclusion
rate of DTP in broiler diets (Persia et al., 2003;
King and Zeidler, 2004; Jafari et
al., 2006) could be due to several factors including origin of the farm
(area, state), soil conditions and use of fertilizers, means of irrigation,
variety of tomato, ripeness, tomato processing conditions and cannery plants,
relative percentage of seed, skin, pulp and leaves in wet pomace and many more
factors related to drying process. These factors can influence the degree of
nutrient digestibility of DTP and consequently its nutritional value and impact
on productive traits of broiler chicks.
In this study, the results of the current study indicate that dried tomato pomace can be practically applied into broiler diets up to 3, 6 and 9% with a multi-enzyme supplementation in the starter, grower and finisher phases respectively, without experiencing any harmful effects on productive and carcass characteristics.