|Nisbet, David - Dave|
Submitted to: Poultry Science
Publication Type: Peer reviewed journal
Publication Acceptance Date: 12/12/2006
Publication Date: 5/20/2007
Citation: Dunkley, K.D., Dunkley, C.S., Njongmeta, N.L., Callaway, T.R., Hume, M.E., Kubena, L.F., Nisbet, D.J., Ricke, S.C. 2007. Comparison of in vitro fermentation and molecular microbial profiles of high-fiber feed substrates incubated with chicken cecal inocula. Poultry Science. 86:801-810. Interpretive Summary: Diets high in fiber help egg-laying hens retain and/or promote populations of beneficial intestinal bacteria during periods of limited access to high energy feeds such as during induced molt. Induced molt is used to extend the egg-laying period and hens often lose populations of beneficial intestinal bacteria, which have been shown to protect against bacteria that cause illness in humans. This study was conducted to investigate and compare the effects of feeds high in dietary fiber on egg-laying hen intestinal metabolic acid production and bacterial populations. Diets examined included soybean meal, soybean hulls, beet pulp, wheat middlings, ground sorghum, cotton seed meal, 100% alfalfa meal, 90% alfalfa + 10% commercial layer ration, 80% alfalfa + 20% commercial layer ration, and 70% alfalfa + 30% commercial layer ration. Intestinal bacteria and high fiber feeds were placed in test tubes and incubated. The results revealed that alfalfa-based diets yielded higher levels of metabolic acids. A molecular technique was used to determine the kinds of bacteria present in the intestine of each group of chickens. Bacteria present in the alfalfa-based diets were very similar to each other and were different types than those in the other diets. These data suggest that high alfalfa fiber diets may contribute to high levels of metabolic acids and high levels of beneficial bacteria in the intestine of egg-laying hens during periods of low feed availability. These results are of interest to egg producers, egg production researchers, and the egg industry. Results indicate the benefits of high fiber and alfalfa diets in the production of beneficial metabolic acids and protective intestinal bacteria in egg-laying hens during induced molt and periods of limited access to high energy feeds and may assist in continuing to provide consumers with high quality poultry products.
Technical Abstract: High fiber diets and non-starch polysaccharides have received more interest recently in poultry diets for retaining and /or promoting beneficial gastrointestinal microbial populations during nutritionally stressful management practices. The objective of this study was to investigate and compare the in vitro potential fermentability of high fiber feed substrates (HFFS) that could be used to formulate alternative low energy high fiber molting diets. Feeds examined included soybean meal, soybean hull, beet pulp, wheat middling, ground sorghum, cotton seed meal, 100% alfalfa meal, 90% alfalfa + 10% commercial layer ration (A90), 80% alfalfa + 20% commercial layer ration (A80), 70% alfalfa + 30% commercial layer ration (A70). Cecal contents and HFFS were placed anaerobically in serum tubes and incubated at 39 deg C for 24 h. Samples in two trials were analyzed at 0 and 24 h for short chain fatty acids (SCFA). SCFA in samples at 0 h were subtracted from 24 h samples to determine the net production of SCFA. Acetate, propionate and butyrate were the predominant SCFA, while there was less isobutyrate, valerate. The results revealed that alfalfa based samples yielded consistently higher SCFA levels, A90 in Trial 2 yielded the highest (231.47+/-30.66 umoles/mL) acetate production followed by soybean meal (213.36+/-6.84 umoles/mL). A Polymerase Chain Reaction-based Denaturing Gradient Gel Electrophoresis (DGGE) method based on 16S rRNA gene amplification was also used to determine the bacterial profile of each sample after fermentation. DGGE results from both trials indicated variation in microbial populations and dendrograms of amplicon band patterns demonstrated 69 and 71% similarity for comparison of all feed mixtures in trials 1 and 2, respectively. All alfalfa-based HFFS exhibited a higher similarity coefficient in trial 2 than trial 1 with a band pattern that revealed a 90% similarity and A92 and A82 formed a sub-group showing a 94% microbial similarity coefficient. These data suggest that high fiber sources may be a contributing factor in the level of fermentation that occurs in the ceca and the cecal microbial diversity exhibited by laying hens. Furthermore, dietary fiber fractions may be fermented by cecal microorganisms to form net production of SCFA, which could be a major contributor to microbial fermentation patterns in ceca of poultry.