Paul J. Kononoff
Date of this Version
Dufour, E. I. 2017. Advancing chemical characterization of feedstuffs commonly included in dairy cow rations. MS Thesis. Univ. of Nebraska, Lincoln.
Chemical composition of feedstuffs commonly included in dairy cow rations is variable within a feed type, which raises a potential for nutrient inadequacies for an animal. There are multiple methods to characterize and determine chemical composition including in vitro and in situ methods, as well as refining processing procedures to produce a consistent feed product. Feed component digestibilities can also be evaluated using similar methods.
Research reported in Chapter 2 focuses on characterizing chemical composition and determining the digestibility of fiber and protein fractions of corn dried distillers grains with solubles (DDGS) originating from seven different production sites across Michigan, South Dakota, and Nebraska. Results indicate that chemical composition of DDGS, including amino acid composition and fatty acid composition, differed significantly among sources suggesting that processing procedures are variable and frequent analysis of chemical composition should be conducted to ensure quality control. Protein digestibility was determined using the Ross et al. (2013) method, with significant differences being reported among DDGS samples in the areas of rumen-undegradable protein (RUP), RUP digestibility, and total-tract digestible protein on both a crude protein and dry matter basis. Fiber digestibility was determined through a series of varying in vitro incubation periods, as well as using the Combs (2013) method of in vitro total-tract neutral detergent fiber digestibility. Significant differences were observed across all DDGS samples for protein and fiber digestibility estimates across production sites.
Chapter 3 describes the second experiment, focusing on quantifying the extent of microbial contamination of eleven different feedstuffs with varying chemical compositions. Feeds used in this study included alfalfa hay, bloodmeal, wet brewers grain, canola meal, citrus pulp, corn silage, corn dried distillers grains with solubles, grass hay, soybean meal, soy hulls, and SoyPass®. Samples were weighed into nylon bags and ruminally incubated for 16 hours to determine DM digestibility (DMD) and the RUP fraction. After ruminal incubation, samples were lightly rinsed, DNA was extracted, and concentrations of DNA were obtained using spectrophotometry. DNA samples were then run through a droplet digitial polymerase chain reaction procedure in order to quantify the extent of microbial contamination on each feed sample. As expected, chemical composition and DMD differed across feedstuffs. Microbial contamination upwardly biased RUP estimates and the extent of this contamination differed across feedstuffs, suggesting there may be an opportunity to increase our understanding of chemical composition of dietary components and the effect they have on the extent of microbial contamination.
Advisor: Paul J. Kononoff