Browsing by Author "Walk, Carrie L."

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    Effects of Calcium and Enzyme Supplementation on the Occurrence of Necrotic Enteritis
    Paiva, Diego Moreira (Virginia Tech, 2013-01-21)
    Diet composition and nutrient balance can have a critical impact on intestinal integrity during exposure to enteric pathogens. Researchers have extensively reported benefits on nutrient availability and broiler performance as a consequence of the impact of phytase supplementation. However, the poultry industry has little information on the effects of phytase supplementation in disease settings. The objective of these studies was to evaluate phytase supplementation impact on bird performance, intestinal morphology and pH, nutrient digestibility and bone mineralization during necrotic enteritis (NE). In each experiment, Cobb 500 broilers were obtained from a commercial hatchery and housed in floor pens at the Virginia Tech Turkey Research Center. Birds were placed on used litter from a previous flock that had presented clinical signs of NE. Broilers were fed non-medicated diets formulated to meet NRC (1994) nutrient requirements, except for calcium and phosphorus. In the first experiment, birds began exhibiting clinical signs of NE on d 9, and elevated NE-associated mortality persisted until d 26. Mortality was influenced by the main effects of dietary Ca or phytase. Dietary Ca supplemented at 0.9% or 1000 FTU/kg of phytase increased mortality compared to 0.6% Ca or 0 FTU/kg phytase, respectively, from d 0 to 19. Feed intake (FI) and feed conversion (FC) were affected by Ca x P interaction. From d 0 to 19, birds fed 0.9% Ca and 0.3% available P (avP) had decreased FI and improved FC compared to birds fed 0.9% Ca and 0.45% avP, while FI and FC were similar in birds fed diets with 0.6% Ca, regardless of avP level. Calcium x P x phytase interaction influenced BW or BWG from d 0-12. In general, birds fed 0.9% Ca and 0.45% avP with phytase were heavier compared to birds fed 0.6% Ca, 0.45% avP, and phytase. Calcium at 0.9% increased gizzard (d 19) and jejunum (d 12) pH. Dietary Ca supplemented at 0.9%, avP supplemented at 0.45%, and 1,000 FTU/kg phytase significantly increased tibia ash weight compared to 0.6% Ca, 0.3% avP, and 0 FTU/kg phytase, respectively, on d 12. A 3-way interaction was observed on d 35 for tibia ash percentage; birds fed 0.9% Ca and 0.45% avP had a significant increase in tibia ash percentage, regardless of phytase supplementation. A 3-way interaction was also observed for Ca and P digestibility on d 35. Phytase supplementation significantly increased Ca digestibility regardless of Ca and P levels of the diets. In addition, diets containing 0.6% Ca and 1,000 FTU/Kg of phytase resulted in a significant increase in P digestibility, regardless of P levels. In the second experiment, birds also began exhibiting clinical signs of NE on d 9, and elevated NE-associated mortality persisted until the end of the trial (d 21). Mortality was significantly affected by an interaction between Ca source and Ca levels. Significantly higher mortality was observed when animals were fed 0.9% Ca diets formulated with calcified seaweed from d 0-21 compared to 0.6% Ca diets (regardless of Ca source). From d 0-7, birds fed 0.6% Ca in diets supplemented with phytase had heavier BW than the other treatments regardless of Ca source. From d 0-14 and 0-21, animals fed diets with calcified seaweed had significantly higher FC than animals fed diets with limestone. On d 21, the gizzard of birds fed 0.9% Ca was significantly less acidic than the gizzard of birds fed 0.6% Ca. In conclusion, reducing dietary levels of Ca associated with phytase supplementation improved bird performance and nutrient digestibility. In addition, these experiments indicate that Ca is an important dietary factor in the pathogenesis of NE.
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    Effects of dietary enzyme supplementation on performance, bone ash, small intestinal morphology, and apparent ileal amino acid digestibility of broilers exposed to a live coccidia oocyst vaccine
    Walk, Carrie L. (Virginia Tech, 2009-09-03)
    A series of experiments were conducted to evaluate the effects of dietary enzyme supplementation in broilers exposed to a live coccidia oocyst vaccine. In each experiment, Cobb 500 broilers were obtained at day of hatch from a commercial hatchery. Half of the chicks were sprayed with Coccivac BTM and housed in battery brooders in experiment (EXP) 1 and 2 or floor pens (EXP 3). Experimental diets were formulated according to Cobb 500 nutrient recommendations (positive control; PC) with the exception of Ca and available P (aP), which were reduced in the negative control (NC) diets approximately 0.1% (EXP 1), 0.11 and 0.13%, respectively (EXP 2), and 0.13% (EXP 3). Negative control diets in EXP 1 were supplemented with phytase (PHY), protease (PRO), xylanase (XYL), and the combination of PHY+PRO, PHY+XYL, and PHY+PRO+XYL. Negative control diets in EXP 2 were supplemented with PHY A, PHY B, and PHY C. In EXP 3, PC diets were supplemented with PHY at 1000 FTU/kg, and NC diets were supplemented with PHY at 1000 or 5000 FTU/kg. In all three experiments PHY supplementation generally improved (P ≤ 0.05) broiler performance and bone ash. Vaccination reduced (P ≤ 0.05) broiler performance in EXP 1 and 3, but increased (P ≤ 0.05) broiler performance in EXP 2. Xylanase and/or PHY supplementation tended to improve (P = 0.10) ileal amino acid digestibility (IAAD) in vaccinated broilers in EXP 1 and EXP 3. Phytase supplementation improved (P ≤ 0.05) IAAD and vaccination reduced (P ≤ 0.05) IAAD in EXP 3. Small intestinal morphology and goblet cell numbers were affected by enzyme supplementation and vaccination, which resulted in significant (P ≤ 0.05) interactions. In general, vaccination increased (P ≤ 0.05) small intestinal crypt depth and reduced (P ≤ 0.05) goblet cell numbers in EXP 3. Phytase supplementation of the NC diets fed to vaccinated broilers ameliorated the reduction in ileal goblet cells associated with vaccination (EXP 3). Enzyme supplementation tended to improve nutrient digestibility and altered small intestinal morphology in vaccinated broilers. Vaccination reduced broiler performance but nutrient digestion and dietary enzymes may improve nutrient utilization during a coccidia vaccination.