Background and Objective: In the USA, consumer demand has led to the reduction in use of all antibiotics, including ionophores. The broiler industry, in turn, has relied upon coccidiosis vaccines and chemicals as the means of reducing the effects of coccidial infection. Because these products are limited by incomplete anticoccidial activity and/or inconsistent performance results, they are frequently supported by phytochemical products to improve their efficacy. The objective of the current study was to determine the effects of a quillaja and yucca saponin combination (QY) on lesion scores, performance and mortality when broilers were fed 3 chemical programs or a coccidiosis vaccine in a disease challenged, floor pen environment. Materials and Methods: Using randomized complete block designs, 2 identical trials were conducted involving a total of 9,900 Ross 708 broilers. A non-medicated control, 3 commonly-used chemical programs (nicarbazin, nicarbazin: decoquinate and zoalene) and a coccidiosis vaccine were evaluated; these treatments were fed in the absence and presence of QY. Growth performance, coccidial lesion scores and total mortality were primary variables evaluated. Treatments were replicated 10 times in each test and all data were combined prior to statistical analysis. Results: During the first 28 days of testing, addition of QY improved growth performance, lesion scores and mortality of each anticoccidial program. In addition, pooled results across all treatments demonstrated that QY significantly improved final growth measurements and mortality. Conclusion: In the face of an intestinal disease challenge, QY improved coccidial lesion scores and mortality of 3 chemical programs and a coccidiosis vaccine. This reduction in coccidial exposure contributed to improved growth responses compared to all non-QY treatments.
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Coccidiosis remains one of the most significant diseases affecting poultry production globally. It is well-recognized that infection with Eimeria parasites occurs in every location where chickens are raised and these infections influence growth, feed efficiency, mortality and the susceptibility to other diseases. As a result, the economic impact of coccidiosis is likely greater than any other disease affecting poultry production, with a recent global estimate of costs in the range of 15 billion USD annually1. This fact underscores the requirement for effective methods of coccidiosis control in order to minimize these adverse effects.
In the United States, poultry veterinarians consider coccidiosis the disease of greatest importance in broiler and layer production and often express concerns related to the lack of products needed to control the disease2. This scenario has been worsened in recent years by marketing programs that restrict the use of antibiotic-based health programs. Thus, in order to comply with consumer demands for antibiotic-free poultry products, use of the polyether ionophorous antibiotics and their combinations with nicarbazin has ceased in antibiotic-free production. Recent reports2,3 indicate that the reductions in ionophore usage brought about by these marketing initiatives have elevated the levels of coccidial infection normally observed and have led to a greater incidence of bacterial complications such as necrotic enteritis.
In the absence of ionophore-based prevention programs, the American industry has relied upon older, chemically synthesized anticoccidials (referred to as “chemicals”) and live coccidiosis vaccines as the means of controlling Eimeria infections1,2. Inherent in these changes, however, are concerns related to product efficacy, zootechnical performance and consistency of the anticoccidial response. To assuage these concerns, broiler producers have turned to phytonutritional (eubiotic) feed additives which may provide benefits in the control of Eimeria, reduce bacterial sequalae or exert undefined effects in the intestinal milieu.
Saponins are plant-derived compounds known to exert numerous biological activities4. Investigation of these biological effects in animals has shown that saponins can reduce pathogen loads, influence nutrient uptake, reduce ammonia production and affect the growth process4,5. Although the original proposal for evaluating the effects of saponins on coccidial infections was made more than 20 years ago5, recent research has shown that combinations of saponins derived from Quillaja saponaria (the Chilean soapbark tree) and Yucca schidigera (a desert plant of the American southwest) diminished the adverse effects of Eimeria infections in broilers6. Because this saponin combination has become a frequently used feed supplement that assists in the maintenance of intestinal health in commercial broilers, evaluating its effects in typical American antibiotic-free anticoccidial programs was needed. Thus, the objectives of the current work were to evaluate the effects of the quillaja and yucca saponin combination (QY) when fed concurrently with 3 chemical anticoccidial programs that are often used in American production. In addition, the combined effects of QY with a live, partially attenuated coccidiosis vaccine were also tested.
MATERIALS AND METHODS
The experiments carried out in this trial series were conducted at AHPharma, Inc., Hebron, Maryland, USA. All birds used in these tests were reared under the animal welfare guidelines specified by the Animal Care and Use Committee of AHPharma, Inc. Birds were humanely euthanized by cervical dislocation using procedures approved by the committee noted above.
The quillaja and yucca-based product tested in this series of trials was sourced from Quillaja saponaria trees and Yucca schidigera plants. This combination is a commercially prepared product (Magni-Phi®, Phibro Animal Health Corp., Teaneck, New Jersey, USA) that consists of 100% ground plant material that is formulated in a proprietary ratio where quillaja is the major component. No excipients, carriers or extracted materials are used in the product. Thus, unaltered quillaja saponins supplemented with the saponins naturally contained in yucca comprise the active ingredients of the product. Additional product information has been presented previously6.
The anticoccidial products and the coccidiosis vaccine evaluated in these tests are commonly-used methods for the control of coccidiosis in the USA. The products nicarbazin, (Phibro Animal Health Corporation, Teaneck, NJ, USA), decoquinate and zoalene (Zoetis Animal Health, Durham, NC, USA) were acquired commercially and administered at approved dosage levels in feed. In the case of the live coccidiosis vaccine (VAC), Coccivac B52 (Merck Animal Health, Madison, NJ, USA) was applied by spray at the hatchery according to the instructions outlined by the manufacturer. Following vaccine application, adequate time was allowed for the consumption of vaccinal oocysts to ensure optimal results.
Two floor pen trials of identical design were conducted. In addition to a non-medicated control, 4 additional anticoccidial programs were tested: nicarbazin (NIC:NIC, 125 ppm in starter feed, 100 ppm in grower feed); nicarbazin:decoquinate (NIC:DEC, 125 ppm NIC in starter, 30 ppm DEC in grower); zoalene (ZOL, 125 ppm in starter and grower feeds) and a live coccidiosis vaccine (VAC, Coccivac B52). In addition, each of these 4 programs was evaluated in the presence of QY (250 ppm), administered in feed from placement until trial termination. In both tests, completely randomized block designs were employed utilizing 10 blocks in each trial. Fifty-five Ross 708 broilers were assigned to each pen at day-of-hatch and grown until day 42. Together, the trials involved 9,900 broilers.
Diets used in the tests were standard corn-soy based commercial rations formulated to meet or exceed the nutrient requirements of growing broilers7. Specific dietary ingredients and proximate analyses of these feeds have been reported previously8. Consistent with many feeding regimes used in the USA, a feeding plan involving starter, grower and finisher feeds was employed in which starter was fed to day 14, grower until day 28 and finisher rations from day 29-42. Since many commercial programs in the USA limit the use of anticoccidial products to starter and grower feeds, a similar approach was used in the current study. That is, finisher feeds used in these tests did not contain anticoccidial products. However, the experimental design shown above illustrates that QY (250 ppm) was fed for the duration of the tests. No antibiotics of any type were administered during these tests and management procedures used in both trials were consistent with methods used in commercial US broiler production.
As is typical in US commercial production, all birds in these trials were reared on used, built-up litter. Since the litter conditions used in each trial were designed to induce an enteric disease challenge, each pen was also supplemented with litter that was collected from commercial broiler farms in the Delmarva region of the United States. The farms were known to have had consistent production difficulties with coccidiosis; further analysis of this litter indicated that the spores of Clostridium perfringens were present as well. Prior to the start of each trial, 5 kg of this litter were mixed into the existing litter in each pen in the test facility. In addition, the sporulated oocysts of E. acervulina and E. maxima (1×105 and 3.5×104 per bird, respectively) were added to the litter contained in each pen. The pathogenic nature of this challenge was confirmed through scoring of coccidial and clostridial lesions at several points in each trial. As an indicator of the severity of the intestinal challenge, the mean mortality of the control treatment was approximately 2 times greater than American industry standards.
Body weight gain and feed conversion values were determined at both 28 and 42 days of testing, such that the timing of the interim measurements was coincident with changes from anticoccidial medication (at day 28). As a result, final results are presented in terms of the anticoccidial method applied in starter and grower (each chemical program or vaccine) and whether QY was administered as part of the feeding program. Bird mortality was evaluated daily but is expressed as percent mortality from all causes recorded from day 0-28 and percent total mortality recorded throughout the entire test period (day 0-42). Coccidial lesion scores were evaluated in 4 birds per pen on days 21 and 28 using the procedures described by Johnson and Reid9. Lesions produced by E. tenella were recorded at both time points in these trials, however, the scores recorded were quite mild. Since all scores were 0.5 or less and showed no differences between treatments, E. tenella lesion scores were not included.
Statistics: The statistical analyses were conducted on data from 2 trials collected during the winter of 2020. Since experimental treatments, animals, pens, facilities, rations and study methods in both tests were the same, trial results were combined. Consequently, each treatment mean presented represents results of 20 replicates (10 replications per treatment per trial). In addition, a combined analysis comparing the means of control pens to those receiving QY and those fed in the absence of QY is presented in Table 4. In this evaluation, the means of 20 control pens were compared to the means of 80 replications utilized in both QY-fed and non-fed treatments. Differences in group means of combined QY-fed and non-fed treatments were tested with one-way ANOVA; statistical differences between individual treatments were determined by Tukey’s HSD to account for multiple testing. In all cases, the threshold of p<0.05 was used to determine whether outcomes were statistically different. All statistical analyses were conducted using the R statistical software10.
The lesion scores recorded for non-medicated controls at 21 and 28 days indicate that a meaningful intestinal coccidiosis challenge was produced in these tests (Table 1). In addition, the majority of the mortality occurred during the first 28 days (Table 2 and 3), indicating that the pathogenic effects of the challenge were greatest in younger birds. Compared to controls, all chemical anticoccidials and the VAC reduced duodenal and ileal lesion scores at day 21 and day 28 (Table 1). At these same intervals, the lesion scores of the VAC program were significantly greater than those of the chemical anticoccidials. At day 21, E. acervulina lesions for the NIC:NIC program were significantly lower than those for ZOL.