This study compared five commercially available probiotics vis-à-vis antibiotic growth promotant (AGP) supplementation and absence of feed additive based on efficiency, intestinal morphometry, and energy digestibility in improving broiler chicken production. A total of 630 straight run (Cobb) day-old broiler chicks were distributed to seven treatments following a completely randomized design, with ten replicates per treatment and nine birds per replicate per cage. Dietary treatments consisted of basal diet in combination with the following: without probiotics and AGP supplementation (treatment 1); 75 ppm each of chlorotetracycline (CTC) and Zn bacitracin (treatment 2); probiotic A, Bacillus subtilis (treatment 3); probiotic B, Bacillus subtilis (treatment 4); probiotic C, Enterococcus faecium (treatment 5); and probiotic D, Bacillus subtilis (treatment 6); probiotic E, Enterococcus faecium, Bifidobacterium spp., Pediococcus spp., and Lactobacillus spp. (treatment 7). At day 42, energy digestibility was determined by fasting three randomly selected birds from each treatment for 12 h and then subjecting them to their corresponding dietary treatments. Excreta were collected and pooled after 24 h of feeding. Pooled excreta were weighed, oven-dried, and subjected to energy analyses after 3-day collection. Apparent total tract metabolizable energy was then computed. At day 47, three birds were randomly selected per treatment for intestinal morphometry (villi height and crypt depth) of the duodenum, jejunum, and ileum. Dietary supplementation using probiotics showed no significant effect on overall body weight, weight gain, feed consumption, feed efficiency, dressing percentage, mortality, harvest recovery, carcass quality parameters (e.g., meat to bone ratio and abdominal fat content), intestinal morphometry, and energy digestibility. Birds under treatment 7 (basal feed + probiotic E) generated the highest income over feed and chick cost.
相似文献Bed shear stress and turbulence quantities are important parameters to understand sediment erosion, transport, and hydraulic processes in most hydraulic studies. An experimental investigation was conducted to understand the effect of injection on the bed shear stress and turbulence characteristics of flows during low sediment transport rate in a closed conduit, which is similar in construction to the erosion function apparatus. In particular, the effect of injection on the bed shear stress, mean velocity profiles, turbulence intensities, Reynolds shear stress, and higher-order moments of the closed conduit flows in the seepage zone as well as at the upstream edge of the seepage zone was examined. The instantaneous velocities were measured using two-dimensional particle image velocimetry (PIV) to evaluate the turbulence structure in both the seepage zone and at the upstream edge of the seepage zone. The bed shear stress estimated by the Reynolds shear stress approach was found to be more appropriate than that estimated by the usual logarithmic law approach. However, a spatial fluctuation in the bed shear stress was noticed as the injection intensity was increased. Injection was found to decrease the velocity near the bed and to increase the velocity near the center of the conduit in comparison to the no-seepage condition in both zones. The injection resulted in more of a decrease in bed stability in the seepage zone in comparison to the upstream edge of the seepage zone as the injection intensities were increased. The introduction of injection increased the magnitudes of the various turbulence parameters in comparison to the no-seepage condition in the seepage zone. The effect of injection was not only visible in the near-bed region, but in both zones as the water depth (measured from top of the sediment surface) increased.
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Habitat fragmentation is known to be one of the leading causes of species extinctions, however few studies have explored how habitat fragmentation impacts ecosystem functioning and carbon cycling, especially in wetland ecosystems.
ObjectivesWe aimed to determine how habitat fragmentation, defined by habitat area and distance from habitat edge, impacts the above-ground carbon cycling and nutrient stoichiometry of a foundation species in a coastal salt marsh.
MethodsWe conducted our research in a salt marsh in the Mid-Atlantic United States, where the foundation grass species Spartina patens is being replaced by a more flood-tolerant grass, leading to highly fragmented habitat patches. We quantified decomposition rates, live biomass, and litter accumulation of S. patens at patch edges and interiors. Additionally, we measured relevant characteristics (e.g., habitat area, elevation, microclimate) of S. patens patches.
ResultsHabitat edge effects, and not habitat area effects, had distinct impacts on ecosystem functioning. Habitat edges had less litter accumulation, faster decomposition rates, a warmer and drier microclimate, and lower elevations than patch interiors. Patches with low elevation edges had the fastest decomposition rates, while interiors of patches at any elevation had the slowest decomposition rates. Notably, these impacts were not driven by changes in primary production.
ConclusionHabitat fragmentation impacts the above-ground carbon cycling of S. patens in coastal wetlands by altering litter decomposition, but not primary production, through habitat edge effects. Future research should investigate whether this pattern scales across broader landscapes and if it is observable in other wetland ecosystems.
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