Effects of Varying Levels of Processed Distillers Solubles and Distillers Grains with Solubles on Nitrogen and Energy Metabolism of Beef Steers

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Abstract
A series of nine metabolism studies were conducted with growing beef steers in switchback or latin-square designs to evaluate the effect of (1) screened process distillers solubles (SDS), (2) screened process distillers grains with solubles (SDGS), (3) centrifuged process distillers solubles (CDS), (4) centrifuged process distillers grains with solubles (CDGS) and (5) screened process distillers grains (SDG) on nutrient digestibility, urea nitrogen and energy utilization. The effect of SDS on blood urea and plasma amino acids was also investigated. Semi-purified diets composed of corn, corn cobs, corn starch, cellulose, urea, minerals and vitamins were used; urea furnished approximately 40% of the dietary nitrogen. Levels of 0, .25, .50 or 1% CDS or SDS and 0, 1, 2.5 or 5% CDGS or SDGS were utilized; only 2.5% SDG was compared against none. The results of these experiments can be summarized as follows: (1) 5% SDGS addition increased (P<.05) nitrogen digestibility (67.2 is 65.5%). (2) One-half percent SDS in the diet increased (P<.10) percent digested nitrogen retained (42.01 vs 39.21%). (3) One-half percent SDS in the diet reduced (P<.05) blood urea (16.86 vs 13.57 mg/100 ml) suggesting a better urea utilization. Plasma cystine, tyrosine and arginine were reduced; plasma glycine, alanine, isoleucine, leucine and lysine were increased nonsignificantly (P<.05); but valine increased significandy (P<.05) due to the addition of SDS. (4) One-half percent of CDS in the diet had no significant effect on digested nitrogen retained (49.3 7 vs 49.79%). (5) Addition of SDGS at 5.0% level to the diet increased (P<.01) both dietary nitrogen retained (37.67 vs 32.64%) and digested nitrogen retained (56.01 vs 49.87%). (6) Both 2 1/2% and 5% CDGS in the diet increased digested nitrogen retained (50.51 vs 48.69%) nonsignificantly (P<05). These data suggest that most of the nutritional factor(s) exists in the SDS. Centrifugation of stillage reduced its activity in the subsequent distillers solubles. Since CDS and SDG had litde effect on nitrogen utilization while SDGS and CDGS increased nitrogen utilization, the centrifuge processed distillers grains may contain the nutritional factor(s). Copyright © 1977. American Society of Animal Science . Copyright 1977 by American Society of Animal Science.