Effects of chemical composition variation on the dynamics of ruminal fermentation and biological value of corn milling (co)products

Abstract

The objectives of this study were to evaluate the dynamics of gas production of several corn (co)products, to develop equations to predict the rate of ruminal fiber digestion, to estimate total digestible nutrients (TDN) and net energy for lactation (NE L ), and to assess the stochasticity of chemical composition and nutritive value variability. Four corn milling (co)products were evaluated in this study: high protein dried distillers grains (HP-DDG), corn bran (BRAN) and dehydrated germ (GERM), and a dried distillers grains plus soluble produced with a low-heat drying process (BPX). Alfalfa hay was used as an internal standard feed in the in vitro fermentation dynamics analysis. Standard chemical analyses, in vitro digestibility, and in vitro gas production techniques were used to obtain the necessary physicochemical characterization of feeds. The in vitro dry matter digestibility at 24 and 48 h of incubation decreased exponentially as acid detergent insoluble nitrogen increased. However, the degree of in vitro dry matter digestibility reduction was more accentuated at 24 than at 48 h of incubation. The difference among these feeds regarding the dynamics of the anaerobic fermentation within different substrates (intact feed, and fiber and defatted residues) was evaluated. Results suggested that the proportion of fiber digested in the rumen was affected by the degree of sample processing and fat removal. Fractional fermentation rate (kf) of neutral detergent residue (without sodium sulfite) and defatted fiber residue for BRAN, GERM, HP-DDG, and BPX was estimated to be 0.0635 and 0.0852 h −1 , 0.0803 and 0.0914 h , respectively. The most influential variables affecting kf NDR of HP-DDG and BPX also affected the predicted TDN, suggesting that fiber quality is essential to ensure higher TDN values for these feeds. Our study indicated that it is possible to routinely quantify the rate of fiber digestion and this approach may be based on common analytical procedures namely estimates of neutral detergent fiber, acid detergent fiber, acid detergent insoluble nitrogen, ether extract, and acid detergent lignin. Our simulations of TDN values demonstrated that differences in fermentability and chemical composition of these corn (co)products might considerably affect the supply of energy to lactating dairy cow. The analytical methods developed in this study may serve as a valuable tool to assess nutrient quality and uniformity when samples differ in chemical composition.

Evaluation of in vitro gas production and rumen bacterial populations fermenting corn milling (co)products

“…The in vitro anaerobic fermentation chamber as described by Tedeschi et al (2009) was used to obtain the gas production pattern resulting from the fermentation of the intact or defatted composites. Briefly, the instrument consisted of an incubator with multi-plate stirrers, pressure sensors connected to 125-mL Wheaton incubation bottles, an analog to digital converter device, and a PC-compatible computer with Pico Technology software (Pico Technology, Eaton Socon, Cambridgeshire, UK).…”

“…Understanding the broader effects of feed processing and bacterial population shifts in response to nutrients contained in different corn (co)products may be valuable to improve production efficiency. Tedeschi et al (2009) previously published that defatting corn (co)products increased total gas production, reduced lag time, and reduced rate of fermentation. Our hypothesis is that the defatting process would increase fermentability of corn (co)products and alter bacterial populations.…”

“…As more information about the quality of corn (co)products becomes available, new strategies of (co)product feeding will be developed. Feedstuff processing methods have been shown to affect feed efficiency, production (Anderson et al, 2006), and quality (Powers et al, 1995;Tedeschi et al, 2009). Tedeschi et al (2009) reported that the proportion of fiber digested by rumen microbes in vitro was affected not only by the degree of feed processing but also by fat removal.…”

“…Feedstuff processing methods have been shown to affect feed efficiency, production (Anderson et al, 2006), and quality (Powers et al, 1995;Tedeschi et al, 2009). Tedeschi et al (2009) reported that the proportion of fiber digested by rumen microbes in vitro was affected not only by the degree of feed processing but also by fat removal. The detrimental effects on milk quality of inclusion of unsaturated fat in dairy cow rations (Macleod and Wood, 1972) has led to a proposed method that involves deoiling or defatting (co)products.…”

“…The in vitro gas production (IVGP) technique, as described by Tedeschi et al (2009), is a valuable tool that describes the fermentability of ruminant feeds. It could be advantageous to link rumen bacterial population shifts with these fermentation results, which may increase our knowledge of corn (co)product fermenta-tion dynamics, end-products, and the most efficacious processing method.…”