Introduction
Infectious diseases are one of the several challenges limiting the progress of poultry production [1]. Infectious bursal disease (IBD) constitutes one of these diseases and it plays a significant role by causing serious production and economic losses [2]. Infectious bursal disease virus (IBDV), the causative agent of IBD, is a bisegmented, double-stranded RNA virus belonging to the genus Avibirnavirus in the family Birnaviridae, and has a primary affinity for the bursa of Fabricius (BF). Two serotypes of IBDV (1 and 2) have been identified and within each serotype, antigenic variation was considerable [3,4]. The disease affects mostly 3–8 weeks old chickens resulting in immunosuppression, increased susceptibility to, and decreased vaccination responses against other pathogens [5,6]. The control of IBD has been achieved greatly by vaccination although there are reports of outbreaks despite vaccination [7,8]. Also, the availability of maternal antibodies (MAB) in chicks had provided protection against the disease, but these MABs could interfere with response to vaccinations [9,10].
Despite the damages caused by IBD in the poultry industry, there is no specific effective treatment against the disease [2]. This has led to the trial of different remedies by farmers as the industry must continue to expand. This attempt is in concordance with the adoption of complementary and integrative medicine as a means to provide solutions to some medical problems believed to be without solution [11–13]. With respect to this, the poultry industry has also resorted to exploring this option to minimize losses caused by viral diseases. Consequently, there has been the utilization of supplements that targeted some major clinical manifestations of IBD. These supplements include mixtures containing characterized and/or uncharacterized constituents.
The supplements that have been used by farmers against IBD include Antox® and Bactofort® amongst others. These supplements were documented to mitigate the hematological alterations due to very virulent strain of the virus (vvIBDV) [14] as well as resulted in stronger vvIBDV Ab response [15] in chicks. In spite of these reports, the mechanisms by which these effects are produced remain unclear. Hence, this study evaluated the effects of two supplements (Antox® and Bactofort®) on the rate of IBDV antibody decay and response to a vvIBDV in commercial pullets.
Materials and Method
Study location
This study was conducted in the Department of Veterinary Medicine, Ahmadu Bello University (ABU) Zaria, Nigeria.
Chickens used for the study
A total of 200 1-day-old ISA Brown chicks were obtained from a commercial hatchery located in Ibadan, Nigeria. The chicks were housed in the Poultry Research Pen of the ABU Veterinary Teaching Hospital Zaria. They were brooded on deep litter and provided with a floor space of between 0.10 m2 per bird. Before the arrival of the chicks, the pens were cleaned, washed with water and detergents, disinfected, and fumigated twice at 2 weeks intervals. Also, there were rodent and insect controls. The chicks were provided with feed (chick mash) and water ad libitum.
Supplements used in the study
Supplement A was Antox® (Montajat Pharmaceuticals, Bioscience Division, Dammam 31491, Saudi Arabia) in the liquid form containing Saccharomyces cerevisiae (4.125 × 106 cfu/ml), Citric acid (6 g), Lactic acid (2 g), Vitamins B1 (100 mg), B2 (7.5 mg), B6 (80 mg), and B12 (0.6 mg), Biotin (1.5 mg), Nicotinamide (1 g), CaCl2 (300 mg), KI (4.6 mg), Na2SeO3 (78.8 mg), ZnCl2 (320 mg), FeCl2 (300 mg), MgCl2·6H2O (250 mg), MnCl2 (631 mg), CuSO4 (32 mg), and CoCl2 (3.08 mg).
Supplement B was Bactofort® (Biofeed Technology Inc., Brossand, QC, Canada) in a powdered form containing Lactobacillus acidophilus (77 × 109 cfu/kg), Enterococcus faecium (44 × 109 cfu/kg), Saccharomyces cerevisiae (5,000 × 109 cells/kg), and Bacillus subtilis (2.2 × 109 cfu/kg).
Experimental design
The 200 1-day-old chicks were randomly divided into four groups (A–D), each containing 50 chicks. Chicks in group A were administered Antox® (at 1.5 ml/lin drinking water), and B Bactofort® (12.5 g/25 kg in feed), from 1 day old to 42 days of age, while C (positive control) and D (negative control) were not given any supplement. Groups A, B, and C were challenged at 28 days old with a vvIBDV (Nigerian isolate; 108.46/CID50) at the rate of 0.05 ml/bird via the intra-ocular route. Blood was collected from the chicks on days 1, 7, 14, 21, 28, 35, and 42 of age into labeled tubes and allowed to clot. The serum harvested was analyzed for IBDV for antibody using enzyme-linked immunosorbent assay according to the manufacturer’s protocol (IDEXX Laboratories, Incorporate, Westbrooke, ME 04092).
Data analyses
Data was presented using tables. Antibody titers were expressed as mean ± SE of the mean values (Mean ± SEM). Data was subjected to a one-way analysis of variance followed by Tukey’s multiple comparison posthoc test. The changes in antibody titers were expressed in percentage. GraphPad Prism 5.0 for Windows (GraphPad Software, San Diego, CA) was used for the analysis. Values of p ≤ 0.05 were considered significant.
Results
The Ab titers were highest at 1 day of age in all the groups (Fig. 1). There was a significantly higher (p < 0.05) antibody titer in groups A and B compared to C and D at days 7, 14, 21, 28, 35, and 42 (Fig. 1).
Figure 1.
Mean ELISA antibody titer (log10) level of chicks administered two supplements (Antox® and Bactofort®) from 1 day old and challenged with a vvIBDV at 28 days old.
The rate of antibody decay was lower in groups A (−57.7%) and B (−65.4%) than in C (−72.1%) and D (−74.2%) on day 28 (Table 1). The antibody response rate was higher in groups A (+76.4%) and B (+71.1%) at day 35. There was a lower antibody decline rate in groups A (−22.4%) and B (−29.0%) compared to C (−38.6%) and D (−51.4%) on day 42 (Table 1).
Discussion
The IBD antibody titers in all groups of chicks in this study from 1 to 28 days old indicated that these were MAB as these chicks were not vaccinated against IBD during this period [15–17]. The pattern however showed decreases in the antibody titre in all groups of chicks indicating MAB decay [7,18]. This decay was depicted by the negative % changes from 1 to 28 days old. However, the negative % changes in these antibody titers were lower in groups A and B. Interference with the catabolism of MAB by the constituents of Antox® and Bactofort® individually and/or synergistically might be responsible for this decreased rate of MAB decay. The actions of the microorganisms contained in the supplements might be another possible mechanism [15].
Following infection with vvIBDV, there were significantly higher antibody titer and positive % change in antibody titer in groups A and B compared to group C at 35 days of age. At 42 days of age, there was a decline in antibody titer in all the groups but this decline was lower in groups A and B. This suggests that Antox® and Bactofort® were, therefore, able to elicit stronger antibody responses through probable enhanced production of immunoglobulins by the immune organs. This assumption was because IBDV primarily infects the BF thus causing B-cell lysis with consequent immunosuppression and possible seroconversion [19–21]. In a similar study, there was a significantly higher IBD antibody titer at 5 and 10 days post-inoculation in chicks administered probiotics compared to positive control [22]. In addition, the higher antibody titers might be due to decreased destruction of lymphocytes by vvIBDV as a result of the supplements [14,23].
Table 1.
% Change in ELISA antibody titer (log10) level of chicks administered two supplements (Antox® and Bactofort®) from 1 day old and challenged with a vvIBDV at 28 days old.
| Age of birds (days) | ||||
|---|---|---|---|---|
| Group | Treatment | 28 | 35 | 42 |
| A | Antox® | −57.7 | +76.4 | −22.4 |
| B | Bactofort® | −65.4 | +71.1 | −29.0 |
| C | Positive control | −72.1 | +57.3 | −38.6 |
| D | Negative control | −74.2 | -46.9 | −51.4 |
+=increase; −=decrease.
The higher antibody response with Antox® compared to Bactofort® in this study might be associated with the minerals (such as zinc, magnesium, manganese, copper, and cobalt amongst others) contained in Antox®. The modulation of the immune system and/or regulation of antiviral immunity might be associated with these minerals [24–26] thus the higher immune response. Antimicrobial agents present in the feed used in this study might have distorted the efficacy of Bactofort® thus resulting in its lower antibody responses compared to Antox® [14].
Conclusion
The supplements (Antox® and Bactofort®) decreased IBD antibody decay, enhanced antibody response to vvIBDV infection, and decreased antibody decline by vvIBDV. Therefore, the use of these supplements in IBD outbreaks to enhance immune responses is recommended. However, further studies should be carried out to evaluate different dose regimens of these supplements on IBD and determine their adverse effects when administered to chicks for more than 6 weeks of age.
Conflict of interest
The authors declare no potential conflict of interest.
