|WEBER, THOMAS - Elanco Animal Health, Inc|
Submitted to: Journal of Animal Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/11/2015
Publication Date: 5/1/2015
Citation: Kerr, B.J., Weber, T., Ziemer, C.J. 2015. Dietary marker effects on fecal microbial ecology, fecal VFA, nutrient digestibility coefficients, and growth performance in finishing pigs. Journal of Animal Science. 93:2183-2190.
Interpretive Summary: Indigestible markers are commonly used in animal nutrition studies to evaluate rate of passage and nutrient digestibility with chromic oxide, ferric oxide, and titanium dioxide being the most commonly used markers in swine research. Because added dietary markers are concentrated during the digestion process, approximately 10-fold depending upon the ingredient matrix, microbes residing in the gastrointestinal tract are continually immersed in a marker-rich medium. What is not known, however, is if this marker-rich medium has any impact on microbial ecology and subsequent microbial activity and VFA generation; each of which could impact nutrient digestibility of the diet and ultimately animal performance. This research demonstrated that the inclusion of the diet with chromic oxide, ferric oxide, or titanium dioxide has little to no impact on microbial ecology, fecal ammonia or VFA concentrations, nutrient digestibility, or pig performance indicating they are suitable markers for use in digestion studies. This information is important for animal nutritionists to be confindent that dietary markers have no impact on the microbes residing inside the gastrointestinal tract or on the physiology of the animal, either of which could affect nutrient digestibility and subsequent nutrient utilization.
Technical Abstract: Use of indigestible markers such as Cr2O3, Fe2O3, and TiO2 are commonly used in animal studies to evaluate rate of passage and nutrient digestibility. Yet nothing is known relative to their potential impact on fecal microbial ecology and subsequent VFA generation. Two experiments utilizing a total of 72 individually fed finishing pigs were conducted to describe the impact of dietary markers on fecal microbial ecology, fecal ammonia and VFA concentrations, nutrient digestibility, and pig performance. All pigs were fed a common diet with no marker or with 0.5% Cr2O3, Fe2O3, or TiO2. After 33 d of feeding, fresh fecal samples were collected for evaluation of microbial ecology, fecal ammonia and VFA concentrations, and nutrient digestibility, along with measures of animal performance. No differences were noted in total microbes or Bacterial counts in pig feces obtained from pigs fed the different dietary markers while Archaea counts were decreased (P = 0.07) in feces obtained from pigs fed the diet containing Fe2O3 compared to pigs fed the control diet. Feeding Cr2O3, Fe2O3, or TiO2 increased fecal bacterial richness (P = 0.03, 0.01, and 0.10; respectively) when compared to pigs fed diets containing no marker, but no dietary marker effects were noted on fecal microbial evenness or Shannon-Wiener index. Analysis of denaturing gradient gel electrophoresis gels did not find any clear patterns in banding due to inclusion of dietary markers in pigs diets. There was a reduction in fecal isocaproic acid concentrations in pigs fed any of the dietary markers (P = 0.05), with no other effects of dietary marker on fecal DM, ammonia, or VFA concentrations noted. Pigs fed diets containing Cr2O3 had greater Ca, Cu, Fe, and P (P = 0.02), but lower Ti (P = 0.08) digestibility compared to pigs fed the control diet. Pigs fed diets containing Fe2O3 had greater Ca (P = 0.08) but lower Ti (P = 0.01) digestibility compared to pigs fed the control diet. Pigs fed diets containing TiO2 had greater Fe and Zn (P = 0.09), but lower Ti (P = 0.01) digestibility compared to pigs fed the control diet. No effect of dietary marker on pig performance was noted. Overall the data indicate that the inclusion of with Cr2O3, Fe2O3, or TiO2 have little to no impact on microbial ecology, fecal ammonia or VFA concentrations, nutrient digestibility, or pig performance indicating they are suitable markers for use in digestion studies.