INTESTINAL FLOW OF MICROBIAL PROTEIN AND RUMEN UNDEGRADABLE PROTEIN IN CATTLE FED CORN DISTILLERS GRAINS AND SOLUBLES, WITH EMPHASIS DURING LACTATION

The objectives were to evaluate the use of DNA markers and the effects of dried distillers grains with solubles (DDGS) and in vitro fermentation time on the growth of rumen bacteria and protozoa, and to measure the contribution of yeast originating from DDGS to total microbial crude protein (MCP). Treatments were: 1) CONT, control with no DDGS, but with alfalfa hay, corn silage (CS), ground corn (GC) and soybean meal (SBM) included at 25% (DM basis); 2) RC, 20% (DM Basis) DDGS replacing GC; 3) RS, 20% (DM basis) DDGS replacing SBM; 4) RCS, 20% DDGS replacing 10% GC and 10% SBM (DM basis). For each treatment, 0.5 g of substrate was incubated in vitro in 50 mL of inoculum in duplicate. At 0, 4, 16, 32, 48 and 96 h of fermentation DNA was extracted from each treatment and microbial protein was measured by real-time PCR. Microbial markers used are from the 16S rRNA gene, 18S rRNA gene and the II chromosome; for bacteria, protozoa and yeast, respectively. Data were analyzed as a completely