Necrotic enteritis (NE) is a disease that negatively affects broiler performance and has increasingly become a problem with the reduced use of antibiotics. There is increased interest to utilize alternative methods including coccidial vaccines and direct fed microbials (DFM) to reduce or prevent NE. Additionally, it has been demonstrated that reduced dietary Ca can reduce NE mortality. The objective of the first study was to examine the effects of Bacillus subtilis (DFM) in combination with attenuated (AV) and non-attenuated (NV) coccidial vaccines in broilers with NE. The objective of the second study was to determine the effects of DFM, antibiotic (BMD) or negative control (NC) with standard dietary Ca (0.9%) or below standard Ca (0.75%, 0.6%) in broilers with NE. To induce a natural NE occurrence, birds were vaccinated with the appropriate coccidial vaccine and then placed on reused litter from a previous flock exhibiting NE lesions and mortality. In the first trial DFM reduced BW and BW gain (P ≤ 0.05) during the starter phase (0 to 14 d). The addition of a DFM in the AV group resulted in decreased (P ≤ 0.05) BW gain and BW at 42 d. The DFM in the NV group resulted in improved (P ≤ 0.05) mortality corrected feed conversion ratio from 0 to 42 d. Overall, with a natural NE occurrence, the effect of DFM was variable depending on what type of coccidial preventative was utilized and was beneficial when used with NV. In the second trial BW and BW gain were increased in broilers fed 0.60% dietary Ca and DFM compared to 0.90% Ca and NC (P ≤ 0.05). Broilers fed 0.60% Ca had reduced NE mortality compared to broilers fed 0.90% Ca (P ≤ 0.05). Reducing dietary Ca to below industry standards was able to lessen the severity of NE though the addition of DFM was needed to improve BW. Overall, with a natural NE occurrence, the DFM was beneficial when used with NV and in diets with 0.6% dietary Ca. / Doctor of Philosophy / Necrotic enteritis (NE) is caused by the bacterium Clostridium perfringens and is a disease that reduces growth of broiler chicks and has increasingly become a problem in the chicken industry with the reduced use of antibiotics. Coccidiosis is a protozoal disease that causes intestinal damage and predisposes broilers to developing NE. Prevention of coccidiosis can be through medication or coccidial vaccines. Probiotics or direct fed microbials (DFM) have demonstrated the potential to reduce both coccidiosis and NE symptoms. Additionally, it has been shown that reducing the amount of calcium (Ca) in the diet can reduce chick death from NE. The first study examined the effects of a beneficial bacterium, Bacillus subtilis (DFM) in combination with two types of coccidial vaccines, attenuated (AV) and non-attenuated (NV). The second study investigated DFM with standard dietary Ca (0.9%) or below standard Ca levels (0.75%, 0.6%). To induce a "natural" NE disease occurrence, birds were vaccinated with the appropriate coccidial vaccine and then placed into pens. Pens contained reused litter from a previous flock of birds with NE (contained spores of Clostridium perfringens). In the first trial DFM reduced body weight of broilers during the first two weeks (P ≤ 0.05). The DFM decreased (P ≤ 0.05) BW gain and BW in the AV group but improved feed efficiency in the NV group (P ≤ 0.05). In the second trial BW and BW gain were increased in broilers fed DFM and lower Ca diets (0.6%) compared to those fed the standard (0.90%) Ca diets without DFM (P ≤ 0.05). Dead birds were reduced when broilers were fed lower Ca diets (0.6%) compared to broilers fed standard (0.90%) Ca diets (P ≤ 0.05). In conclusion, the DFM was beneficial when used with NV and in diets with lower Ca (0.6%) during a natural NE occurrence.
| Identifer | oai:union.ndltd.org:VTETD/oai:vtechworks.lib.vt.edu:10919/110439 |
| Date | 03 June 2022 |
| Creators | Calvert, Alamanda J. |
| Contributors | Animal and Poultry Sciences, Persia, Michael E., McElroy, Audrey P., Wong, Eric A., Johnson, Sally E. |
| Publisher | Virginia Tech |
| Source Sets | Virginia Tech Theses and Dissertation |
| Language | English |
| Detected Language | English |
| Type | Dissertation |
| Format | ETD, application/pdf |
| Rights | In Copyright, http://rightsstatements.org/vocab/InC/1.0/ |
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