الفهرس 
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Abstract
In this study, two separate experiments were conducted on broilers. In experiment I, the effect of adding biological feed additives as probiotic, prebiotic and synbiotic with and without feed restriction were evaluated. The second experiment (II) was applied to investigate the impact of feeding the unconventional feeds (potato peels, and sugar beet pulp) with or without enzyme in broilers. In both experiments, the influence of the used feed additives, feed restriction and unconventional feeds on performance, blood parameters, carcass traits and economic efficiency were investigated. Moreover, digestibility rates of the diets were measured in experiment II only.
Materials and methods
Experiment I
Two hundred and forty unsexed one day-old chicks of Arbor Acres breed were used for 8 weeks. Two trials were included, A & B, with 120 birds in each. Every trial was divided into 4 equal groups, each with 30 chicks. The birds in trial A were fed ad libitum throughout the experiment, while the chicks in trial B were fed ad libitum during the first week of age, then subjected to 5 hours/ day of feed restriction from the beginning of the second week up to the end of the experiment. In both trials, the birds in group 1 were fed on a control diet, while the other groups were given the same control diet supplemented either with a probiotic (Enhancer®, at a dosage of 0.250 kg / ton in the three feeding phases) in group 2, prebiotic (Bio–Mos®, at a rate of 2.0, 1.0, & 0.5 kg / ton in starter (0-3 wks), grower (3-6 wks), and finisher (6-8 wks) diets, respectively) in group 3, or synbiotic in group 4. The synbiotic used was a mixture (50:50 by weight) of 0.125 kg/ ton probiotic (Enhancer®) with 1.0, 0.5 & 0.25 kg of prebiotic (Bio-Mos®) in the three phase diets, reaching a total of 1.13, 0.63, 0.38 kg / ton in starter, grower and finisher diets, respectively.
The experimental diets were formulated from the commonly used feedstuffs to satisfy the broiler nutritional needs stated by NRC for poultry (1994) which recommends a metabolizable energy density of 3200 kcal/kg in all the phase-diets and 23, 20 and 18 % crude protein in starter, grower and finisher, respectively. Birds were allowed to have free access to water throughout the experiment.
Experiment II
One hundred and fifty unsexed one-day old chicks (Ross-308) were used for 6 weeks in this experiment and divided into five groups, each of 30 chicks. The chicks in group 1 were fed on the control diet. The birds in groups 2 & 3 were offered diets containing potato peels and sugar beet pulp, as unconventional feedstuffs, at the rate of 15% & 7.5%, respectively, while the chicks in groups 4 & 5 were fed the same diets but with adding the enzymes mixture (Enziver®) at the rate of 0.250 kg / ton. The chicks were fed according to NRC for poultry (1994) on a starter diet (0-3 wks), and then a grower one till the end of the experiment at 6 weeks. Feed and clean water were supplied ad-libitum throughout the experiment. Moreover, a digestibility trial was carried out during the last 5 days of the experiment.
Measured parameters
The parameters measured in both experiments were performance, some blood indices, carcass characteristics and economic efficiency. In addition, the digestibility rates of DM, inorganic matter, crude fiber and ether extract of the diets used in experiment II were determined.
Results
Experiment I (Trial A & B)
1- Birds fed diets supplemented with probiotic, prebiotic and synbiotic in both trials had greater body weight compared with the control ones. Moreover, probiotic and synbiotic fed birds had a greater body weight than birds fed with the prebiotic. The end weight at the eighth week reached a percentage of 128, 108 and 134% of the control group (100%) in the probiotic, prebiotic and synbiotic groups of trial A and 138%, 121%, and 133% in the same groups of trial B, respectively. The body weight of restricted feeding groups was significantly lower than the corresponding ones in the ad libitum trial.
2- The cumulative feed intake during the starter period was not affected among the different experimental groups of both trials. However, it increased during grower and finisher periods in birds fed diets supplemented with biological feed additives compared with the control groups. In trial A, feed consumption at the end of the experiment reached up to 112, 101, and 114% of the control (100%) with the probiotic, prebiotic and synbiotic groups, respectively, while in trial B, the amount of feed consumed in the same groups constituted 130%, 116%, and 122%, respectively, when compared with that of the control.
3- The cumulative FCR in the 8 weeks were 1.70, 1.82, & 1.64 for probiotic, prebiotic, and synbiotic, respectively, compared with 1.94 for the control, with the clearest effect in synbiotic and probiotic groups. While, in trial B the cumulative FCR were 1.60, 1.64 & 1.56 at the end of the experiment in the three additive groups (probiotic, prebiotic, and synbiotic, respectively) compared with 1.71 for the control. The feed efficiency of each additive group in feed restriction trial was higher than its corresponding one in the ad libitum trial.
4- The feed additives in both trials did not affect hemoglobin, serum total protein, albumin, globulin glucose, and cholesterol except the packed cell volume which was increased in the additive treatments with restriction at the end of the experiment. Nevertheless, there was a slight significant decrease in globulin due to restriction. Serum total cholesterol concentration was not affected by feeding regime except a slight decrease in feed restriction at the 8th week of age (132.67 vs. 157.33 mg/dl).
5- The dietary treatments did not influence the carcass yield. However, the relative weights of liver, gizzard and proventriculus, small intestine and bursa of fabricius were found to be increased. The additives decreased the visible fat in the carcass, with more decreasing effect in the additive groups with restriction.
6- The lowest feed cost per kg of weight gain was observed in the birds fed diets supplemented with synbiotic, probiotic and prebiotic. Moreover, feed restriction improved the feed cost of production and economic return in the different groups.
Experiment II
1- The body weight of birds fed diets containing potato peels and sugar beet pulp without enzyme supplementation was significantly lower than the control. Moreover, the body weight of chicks fed sugar beet pulp was significantly lower than that of those fed potato peels. The control group reached a weight of 1836g at the end of the experiment, whereas the birds in groups 2 and 3, reached a final weight of 94% (1734g) and 89% (1635g) of the control, respectively. However, addition of enzymes to the two unconventional feed diets (groups 4 & 5) improved the weight to a great extent, especially with the sugar beet pulp group. At the end of the experiment, the body weight of the chicks fed potato peels and sugar beet pulp with enzyme treatment reached about 108% and 112%, respectively, of the control.
2- During the starter period, the feed intake of birds fed potato peels and sugar beet pulp decreased more than the control. At the grower, the feed intake of potato peels was similar to that of the control, but it was still decreasing in sugar beet pulp. Overall the experimental period, the feed intake of the control group was about 3068g / bird, whereas in the two unconventional feed groups was slightly decreased to reach about 97% (2978g) and 93% (2846g) of the control group. Addition of enzymes increased the feed intake during the starter and grower periods. Overall the experiment, the feed intake in potato peels and sugar beet pulp with enzymes reached about 107% and 110%, respectively, when compared with the control.
3- At the starter period, the FCR of potato peels and sugar beet pulp groups was higher than the control. During the grower, the FCR was higher only in sugar beet pulp, but nearly equal to that of the control in potato peels. Overall the experiment, the FCR was slightly increased in the two unconventional feed groups. However, addition of the enzyme to potato peels and sugar beet pulp improved the conversion ratio to be nearly the same level of the control at the starter, whereas it became lower in both treatments during the grower period.
4- In the digestibility trial, feeding the unconventional feeds decreased DM content of bird excreta but it increased with the addition of enzymes. It did not change the digestibility rate of the ether extract compared to the control, while the addition of enzymes increased it to 78.45and 83.97% with potato peels and beet pulp, respectively, compared with 73.66% in the control. Crude fiber digestibility decreased from 18.91% in the control to 15.0 and 15.23% in the peels and beet groups, respectively, while the addition of enzymes increased it to 22.26 and 31.78% in the two unconventional feeds, respectively.
5- At the end of the starter period, feeding of potato peels or sugar beet pulp without and with enzymes did not affect the concentration of total protein, ALT, AST, triglycerides, high density lipoprotein- cholesterol and very low density lipoprotein- cholesterol. However, the levels of total cholesterol and low density lipoprotein- cholesterol were lower in potato peels and sugar beet pulp with or without enzymes, when compared with the control. Also, at the end of the grower period, there was no effect of potato peels or sugar beet pulp without and with enzymes on the tested blood parameters, except low density lipoprotein- cholesterol.
6- At the end of the experiment, carcass yield and relative breast weight had no significant differences among groups. Moreover, there were no significant differences in the relative weight of liver, heart, spleen and large intestine among the treatments. However, the relative weight of gizzard was higher in sugar beet pulp without or with enzymes. The relative weights of proventriculus and small intestine were higher with the enzyme supplementation groups. However, the relative two ceca weight was the highest in the sugar beet pulp group without enzymes, but no differences were found among the other groups. The visible fat was numerically lower with the unconventional feed diets with or without enzyme compared to the control, but the most prominent effect was noticed in sugar beet pulp diets.
7- The feed cost of weight gain production was lower in potato peels with or without enzyme, but higher in sugar beet pulp and similar to the control in sugar beet pulp with enzyme.
Conclusion
Experiment I
Biological feed additives as probiotic, prebiotic and synbiotic could be routinely added to broiler diets, especially when feed restriction program is followed. It is advised to restrict feed, and add probiotic or synbiotic to increase weight, improve feed conversion rate and get higher economic efficiency.
Experiment II
Potato peels can be used at the rate of 15% in the grower diet of broilers without any adverse effect on the performance. While, the inclusion of sugar beet pulp at 7.5% in the diet resulted in poor growth performance. It is recommended that poultry producers should be encouraged to include the high-fiber feeds as potato peels (15%) and sugar beet pulp (7.5) in the diets with enzymes supplementation. As this can help in improving the broiler production costs and solving the problem of current shortage and rising prices of conventional feed ingredients.