3.1. Body Weight, Feed Intake and Feed Conversion Ratio of Broiler Chickens
Results are shown in
Table 3,
Table 4 and
Table 5. Body weights from week 1 and 2 were highly significant (
p < 0.001) in
T2 group but significantly (
p < 0.05) different in the same
T2 group in week 3 when compared with the control group, respectively. In addition, there was a significant (
p < 0.001) difference in body weight in
T2 and
T3 in week 2 when
T2 and
T3 were compared with
T1 and
T2, respectively. In week 3, significance differences (
p < 0.01) and (
p < 0.05) in body weights were observed between
T2 and
T1, and between
T3 and
T2, respectively. There were significant (
p < 0.01) differences in body weight between
T2 and
T1 and between
T3 and
T1, respectively in week 4. However, in week 5, a significant (
p < 0.05) difference in body weight only exists between
T3 and
T1. There were highly significant (
p < 0.001) differences between
T1 and
T2;
T1 and
T3. In the sixth week of the experiment, there was no significant difference (
p > 0.05) in body weight between the treated groups and the control. Overall, the mean body weight obtained in
T1 (1269 ± 31.17 g) in the sixth week was higher when compared with other experimental groups and the control. Feed intake in week 3 decreased (
p < 0.05) in
T2 and
T3 when compared with the control group. However, there was a significant reduction (
p < 0.01) in FI between
T1 and
T2, and between
T1 and
T3, respectively. In the fourth week, FI decreased (
p < 0.001) significantly in
T2 and
T3 when compared between treated groups, and with the control. A similar trend of decreased (
p < 0.001) in FI was observed in week 5 and 6, respectively. A significant improvement in FCR was recorded in the first (
T1) treatment group. In the sixth week of age, there was significant (
p < 0.05) decrease in feed conversion ratio of broiler chickens in
T1 when compared with the control. The feed conversion ratio of broiler chickens in the sixth week of the experiment for control,
T1,
T2, and
T3 were 0.97, 0.49, 0.64, and 0.53, respectively. Feed conversion efficiency did not differ (
p > 0.05) in all the treatment groups in the 1st week of the experiment. During the six weeks of the experimental period, the percentage of mortality in each group was 24, 12, 20 and 16% for control,
T1,
T2, and
T3, respectively.
The present study revealed that probiotic supplementation had an impact on the body weight of broiler chickens from the fourth week of life. This may be explained as one of the yeast probiotic beneficial effects of promoting a healthy gastrointestinal tract environment by nourishing the enterocytes, improving ileal mucosal development and reinforcing mucosal barrier function through maintaining epithelial integrity. This finding is similar with the result obtained by Zhang
et al. [
5], who reported improve growth rate of male broiler chickens supplemented with
S. cerevisiae. In addition, this finding agrees with the results obtained by several authors [
20,
21] in studies with broiler chickens. The highest body weight was recorded in the experimental group administered with the lowest probiotic concentration (
T1 0.25 mL). This very concentration was directly administered to the birds daily without reconstitution in drinking water. However,
T2 could not cause an increase in body weight as seen in
T3. This probably may be associated with the dose effect in
T3, which is higher than the
T1 dose. This result demonstrated that single strain
Saccharomyces cerevisiae (Antox
® probiotic) supplementation has a more positive effect on body weight when administered in lower concentrations, without being reconstituted in drinking water as prescribed by the manufacturer (Montajat Veterinary Pharmaceutical Co. Ltd., Dammam, Saudi Arabia). Santin
et al. [
22] showed that the cell walls of
Saccharomyces cerevisiae improve nutrient absorption from the intestinal mucosa and suggested that this factor may be responsible for the improvement in performance of broiler chickens supplemented with
S. cerevisiae. A probiotic acts by reducing the feed conversion ratio, resulting in an increase in daily live weight gain [
23], which is achieved through a natural physiological way and improvement of digestion by balancing the resident gut microflora. The differences in final body weight in the sixth week may be associated with differences in feed intake.
Table 3.
Effect of supplemental yeast probiotic on body weight of broilers. Significance difference is indicated by single and double asterisk as: * p < 0.05 vs. control, ** p < 0.01 vs. control, *** p < 0.001 vs. control; C, control group (without probiotic); T1, first treatment group; T2, second treatment group; T3, third treatment group. The data are presented as Mean ± SEM, (n = 30). Significance difference at p < 0.05.
Table 3.
Effect of supplemental yeast probiotic on body weight of broilers. Significance difference is indicated by single and double asterisk as: * p < 0.05 vs. control, ** p < 0.01 vs. control, *** p < 0.001 vs. control; C, control group (without probiotic); T1, first treatment group; T2, second treatment group; T3, third treatment group. The data are presented as Mean ± SEM, (n = 30). Significance difference at p < 0.05.
Week | C | T1 0.25 mL | T2 0.5 mL | T3 1.0 mL | p-values |
---|
1 | 90.97 ± 1.98 | 91.63 ± 1.14 | 67.63 ± 2.45 *** | 89.77 ± 1.61 *** | p < 0.0001 |
2 | 185.4 ± 5.25 | 199 ± 3.84 | 147.9 ± 6.34 *** | 185.4 ± 5.29 *** | p < 0.0001 |
3 | 402.7 ± 12.55 | 425.3 ± 10.13 | 355.4 ± 16.57 * | 407.9 ± 12.48 * | 0.0015 |
4 | 647.4 ± 17.29 | 733.6 ± 13.93 ** | 611.6 ± 23.92 *** | 544.7 ± 18.15 ** | p < 0.0001 |
5 | 886.0 ± 30.77 | 926.5 ± 18.59 | 862.1 ± 38.19 | 804 ± 32.50 * | 0.0322 |
6 | 1157 ± 49.55 | 1269 ± 31.17 | 1141 ± 43.29 | 1143 ± 46.48 | 0.1307 |
Table 4.
Effects of dietary yeast probiotic supplement on feed intake of broilers. Significance difference is indicated by single and double asterisk as: * p < 0.05 vs. control, ** p < 0.01 vs. 0.5, *** p < 0.001 vs. control. C, control group (without probiotic); T1, first treatment group; T2, second treatment group; T3, third treatment group. The data are presented as Mean ± SEM, (n = 30). Significance difference at p < 0.05.
Table 4.
Effects of dietary yeast probiotic supplement on feed intake of broilers. Significance difference is indicated by single and double asterisk as: * p < 0.05 vs. control, ** p < 0.01 vs. 0.5, *** p < 0.001 vs. control. C, control group (without probiotic); T1, first treatment group; T2, second treatment group; T3, third treatment group. The data are presented as Mean ± SEM, (n = 30). Significance difference at p < 0.05.
Week | C | T1 0.25 mL | T2 0.5 mL | T3 1.0 mL | p-values |
---|
1 | 424.3 ± 68 | 574.3 ± 116 | 365.7 ± 33 | 557.4 ± 108 | 0.0395 |
2 | 1161.0 ± 91 | 1175.0 ± 103 | 1097.0 ± 97 | 1089.0 ± 91 | p < 0.0001 |
3 | 2149.0 ± 222 | 2206.0 ± 205 | 1771.0 ± 139 * | 1805.0 ± 137 * | p < 0.0001 |
4 | 2958.0 ± 133 | 3007.0 ± 132 | 2559.0 ± 107 *** | 2579.0 ± 105 *** | p < 0.0001 |
5 | 5379.0 ± 424 | 5521.0 ± 343 | 4342.0 ± 273 *** | 4377.0 ± 271 *** | p < 0.0001 |
6 | 7283.0 ± 116 | 7570.0 ± 173 | 5856.0 ± 65 *** | 6159.0 ± 107 *** | p < 0.0001 |
Table 5.
Effect of supplemental yeast probiotic on feed conversion ratio of broilers. C, control group (without probiotic); T1, first treatment group; T2, second treatment group; T3, third treatment group.
Table 5.
Effect of supplemental yeast probiotic on feed conversion ratio of broilers. C, control group (without probiotic); T1, first treatment group; T2, second treatment group; T3, third treatment group.
Week | C | T1 0.25 mL | T2 0.5 mL | T3 1.0 mL |
---|
1 | 0.16 | 0.21 | 0.24 | 0.22 |
2 | 0.33 | 0.24 | 0.39 | 0.31 |
3 | 0.27 | 0.21 | 0.26 | 0.22 |
4 | 0.33 | 0.22 | 0.30 | 0.52 |
5 | 0.66 | 0.64 | 0.53 | 0.48 |
6 | 0.79 | 0.49 | 0.64 | 0.53 |
In the present study, there were significant differences in feed intake between treated birds and control birds. This may be attributed to improved digestion and absorption of nutrient in the digestive tract due to the presence of live yeast cells of
Saccharomyces cerevisiae. These findings are consistent with a series of experimental studies, which revealed that dietary prebiotics [
24] and probiotics [
25] increase feed intake of broiler chickens. However, it is in contrast with the findings by [
26,
27] who reported that dietary additions of probiotics and organic acid preparations, respectively, did not affect feed intake of broiler chickens. Improvement in feed intake by dietary probiotic and prebiotic supplementation often resulted in improved growth performance. Furthermore, significant differences in feed intake existing between treated birds and the control group may be partly responsible for the variation in growth performance. Nevertheless, the birds supplemented with the lowest concentration of the probiotic were heavier than the birds in other treatment groups with the control (C) inclusive. A significant improvement in feed conversion efficiency was recorded in the first experimental group (
T1) treated with the probiotic. FCR values for broiler chickens treated with 0.25 mL of dietary
Saccharomyces cerevisiae probiotic possessed the highest body weight at the 6th week. These results are in agreement with the findings of Jin
et al. [
28] who reported that although a significant improvement in feed conversion ratio was observed in probiotic-supplemented broilers chickens, the results were inconsistent. Probiotics act by reducing the feed conversion, thereby resulting in an increase in daily live weight gain. This may be attributable to efficient ileal digestibility of nutrients. Szymczyk
et al. [
29] reported a marked reduction in feed conversion efficiency in animals fed 1.5% conjugated linoleic acid-supplemented diet relative to control. In addition, Bansal
et al. [
23] reported significant and better weekly feed conversion efficiency on probiotic supplementation in the diet of commercial broiler chicks.
3.2. Carcass and Organ Weights of Broiler Chickens
Weights and yields for carcasses and some organs of broiler chickens are presented in
Table 3. Birds in
T1 experimental group tended to be heavier than birds in
T2 and
T3 experimental groups. However, they were much heavier (
p < 0.01) when compared with the control group. Weights of the thighs and drum sticks in
T1 were higher (
p < 0.05) when compared with the control group, but the yield percentages were not. Abdominal fat weight was significantly low (
p < 0.001) in all probiotic-supplemented groups when compared with control group. This was consistent with the decreased yield percentages in all the probiotic supplemented groups. There was no significant difference (
p > 0.05) in the weights of the heart and intestine in all the treated groups. In addition, there was no significant difference (
p > 0.05) in the weights of the gizzards, liver, spleen, gall bladder and lungs. The differences in carcass weights of broiler chickens may originate from differences in feed conversion ratio and feed intake. In the present study, the feed conversion ratio was low in
T1 probiotic group (results not included) and this same group recorded the highest body weight in the xith week of the experimental period. These results further corroborated the recent findings that probiotic act by reducing the feed conversion ratio, thereby resulting in an increase in daily live weight gain [
23]. The yeast probiotic in
T1 was more effective in elevating the live weight of broiler chickens followed by
T3 group. This may be explained as the improved digestion and absorption of nutrients in the digestive tract of broiler chickens by the live yeast cells of
Saccharomyces cerevisiae. Abdominal fat represents the main fat deposition in broiler chickens and it seems to be directly related to total carcass fat [
30,
31]. Excess accumulation of abdominal fat means both processing and waste problems, but also indicates inefficient energy use [
32]. In the present study, significant differences were observed in abdominal fat in probiotic-supplemented groups. There was overt decreased in weight of abdominal fat in all the probiotic-supplemented groups, indicating the fact that probiotics enhance efficient energy usage. This study is similar with several studies that reported lowering of abdominal fat by probiotic supplementation [
24,
30,
32,
33]. On the contrary, Bozkurt
et al. [
34] showed that dietary supplementation of prebiotics, organic acids and probiotics had no significant effect on abdominal fat pad accumulation in broiler chickens. The entire mass of the intestine in
T1 group was heavier but not significant than the weights of intestine from other experimental groups. This result disagrees with the findings by Alcicek
et al. [
35], who reported that dietary supplementation of probiotics lowered the weight of the small intestine. In addition, there was no significant effect of the probiotic on the weights of organs like the liver, gizzard and lungs. In some previous findings, dietary prebiotic and probiotic supplementation, respectively, did not increase the liver weights of broiler chickens [
28,
36]. Results of probiotic effect on the carcass and organ weights of broilers are shown below (
Table 6).
Table 6.
Effect of supplemental yeast probiotic on carcass and organ weights of broilers. Significance difference is indicated by single, double and triple asterisk as: * p < 0.05 vs. control, ** p < 0.01 vs. control, *** p < 0.001 vs. control; C, control group (without probiotic); T1, first treatment group; T2, second treatment group; T3, third treatment group. The data are presented as Mean ± SEM, (n = 10). Significance difference at p < 0.05.
Table 6.
Effect of supplemental yeast probiotic on carcass and organ weights of broilers. Significance difference is indicated by single, double and triple asterisk as: * p < 0.05 vs. control, ** p < 0.01 vs. control, *** p < 0.001 vs. control; C, control group (without probiotic); T1, first treatment group; T2, second treatment group; T3, third treatment group. The data are presented as Mean ± SEM, (n = 10). Significance difference at p < 0.05.
Parameters | C | T1 0.25 mL | T2 0.5 mL | T3 1.0 mL | p-values |
---|
Live weight (g) | 1382.0 ± 37.95 | 1678.0 ± 64.34 ** | 1482.0 ± 34.69 | 1515.0 ± 56.08 | 0.0034 |
Carcass weight | 903.5 ± 35.47 | 1094.0 ± 46.68 ** | 987.5 ± 26.82 | 996.7 ± 31.77 | 0.0096 |
% | 65.38 | 65.20 | 66.63 | 65.79 |
Thigh (g) | 270.0 ± 8.65 | 318.6 ± 14.49 * | 298.9 ± 8.11 | 303.8 ± 10.91 | 0.0424 |
% | 29.88 | 29.12 | 30.27 | 30.48 |
Drum stick (g) | 153.9 ± 4.68 | 178.5 ± 7.73 * | 171.5 ± 5.55 | 170.7 ± 3.56 | 0.0368 |
% | 17.03 | 16.32 | 17.37 | 17.13 |
Abdominal fat | 9.10 ± 0.18 | 6.60 ± 0.16 *** | 7.60 ± 0.16 *** | 7.10 ± 0.23 *** | p < 0.0001 |
% | 1.01 | 0.60 | 0.77 | 0.71 |
Gizzard (g) | 45.00 ± 4.79 | 57.50 ± 2.32 | 54.80 ± 2.34 | 56.30 ± 3.89 | 0.1050 |
% | 4.98 | 5.26 | 5.55 | 5.65 |
Liver (g) | 44.50 ± 1.92 | 45.80 ± 1.98 | 47.10 ± 1.96 | 50.00 ± 1.76 | 0.1455 |
% | 4.93 | 4.19 | 4.77 | 5.02 |
Heart (g) | 9.40 ± 0.45 | 10.40 ± 0.52 | 9.40 ± 0.31 | 10.90 ± 0.32 | 0.0376 |
% | 1.04 | 0.95 | 0.95 | 1.09 |
Lungs (g) | 10.70 ± 0.42 | 11.80 ± 0.49 | 10.80 ± 0.51 | 11.60 ± 0.43 | 0.2633 |
% | 1.18 | 1.08 | 1.09 | 1.16 |
Intestine (g) | 151.7 ± 8.23 | 177.6 ± 7.64 | 157.3 ± 4.64 | 168.0 ± 7.11 | 0.0590 |
% | 16.79 | 16.23 | 15.93 | 16.86 |
3.3. Anti-Oxidant Enzyme Activities and Malondialdehyde Concentration of Broiler Chickens
Results of serum anti-oxidant enzyme activities are shown in
Figure 1. CAT activity was significantly higher (45.53 ± 1.60 U/mL;
p < 0.01) in
T1 when compared with
T2. In addition, there was significant (
p < 0.05) CAT activity in
T3 when compared with
T2. SOD activity in all the treatment groups was not significantly (
p > 0.05) different when compared with the control and treatment groups. GPx activity was greater (43.20 ± 1.02 U/mL;
p < 0.001) in
T1 when compared with
T3 and control group.
Figure 1.
Effect of supplemental yeast probiotic on serum antioxidant enzyme activities of broiler chickens. Significance difference is indicated by single, double and triple asterisk as: * p < 0.05 vs. 1.0, ** p < 0.01 vs. 0.5, *** p < 0.001 vs. control. Data are presented as Mean ± SEM, (n = 15).
Figure 1.
Effect of supplemental yeast probiotic on serum antioxidant enzyme activities of broiler chickens. Significance difference is indicated by single, double and triple asterisk as: * p < 0.05 vs. 1.0, ** p < 0.01 vs. 0.5, *** p < 0.001 vs. control. Data are presented as Mean ± SEM, (n = 15).
In addition, a more significant (p < 0.01) difference in GPx activity exists between T2 and the control. When T1 was compared with T3 and T2 with T3, a significant (p < 0.05) difference was observed between these treatment groups. There was significant (p < 0.05) difference in MDA concentration in T1 when compared with T3.
Anti-oxidant enzymes are most effective when acting synergistically with one another or with other components of the anti-oxidant barrier of the organism when their activity remains balanced. It has been shown that nutrition plays a vital role in maintaining the pro-oxidant-antioxidant balance [
6]. In the present study, there was increased in both catalase and glutathione peroxidase activities. The increased in activity of these antioxidant enzymes may be attributed to the age, colonization resistance, and susceptibility to environmental pathogens of the birds. This is in agreement with the work of numerous scholars [
37,
38] who reported that an increased in the activity of catalase in the blood is caused by environmental burdens to which birds are exposed to during their growth. In addition, most importantly growth processes in early life is characterized with the generation of ROS through cellular division and apoptosis. This is because ROS are considered as the major mediators of oxygen cytotoxicity and as important messengers stimulating cell division and manifesting cellular signaling effects [
10]. A similar study in turkey reported that mannanoligosaccharides a component of
S. cerevisiae used as dietary additive stimulate the mechanisms of oxidative defense and improve the growth performance of the birds [
39]. Krizkova
et al. [
40] showed that mannans from
S. cerevisiae have antioxidative property
in vitro. This suggests that dietary yeast can protect the gastrointestinal tract in ways other than just removing undesirable bacteria. In addition, Kogan
et al. [
41] suggested that yeast cell wall β-glucans may have antioxidant activity. The steady state of SOD activity in the probiotic-supplemented groups may reflect a significant improvement in health and oxidative status of the birds. These findings are contrary to results obtained by Milinkovic-Tur
et al. [
42], who reported increased activities of SOD and CAT in the heart muscles of broiler chickens. Catalase activity, as well as the activity of other anti-oxidant enzymes, depends on the presence of anti-oxidants in the diet. Oxidative damage develops when anti-oxidant potential is reduced and/or when factors contributing to oxidative stress increase [
43,
44]. The increase in GPx activity in
T1 suggests greater oxidative stress. Also, GPx increased activity in
T2 may be attributed to the sodium selenite fraction of the yeast (
S. cerevisiae) probiotic, which partly enhances anti-oxidative activity. The present results further corroborate the existing knowledge on the positive effect of selenium on GPx activity in chicken erythrocytes, blood, muscles and the liver [
45,
46]. GPx displays its activity mainly in the cellular cytoplasm and only about ten percent of activity is displayed in the mitochondria [
47]. In this manner, the safe removal of hydrogen peroxide is attained through the joint action of GPx and CAT. Malondialdehyde level endogenously reflects lipid peroxidation, which is the sequela of diminished anti-oxidant protection as ROS levels increase. MDA level was higher in
T1 (
Figure 2), and this is a direct reflection of GPx activity in
T1. This may be attributed to the probiotic inability to confer adequate anti-oxidant protection against lipid peroxidation during the growth phase of the birds. We are unaware of any research work on
S. cerevisiae as anti-oxidant and used to study oxidative stress during growth in broiler chickens.
Figure 2.
Effect of supplemental yeast probiotic on serum malondialdehyde concentration of broiler chickens. Significance difference is indicated by single asterisk as: * p < 0.05 vs. 1.0. Data are presented as Mean ± SEM, (n = 15).
Figure 2.
Effect of supplemental yeast probiotic on serum malondialdehyde concentration of broiler chickens. Significance difference is indicated by single asterisk as: * p < 0.05 vs. 1.0. Data are presented as Mean ± SEM, (n = 15).