Steam-processed corn and sorghum grain flaked at different densities alter ruminal, small intestinal, and total tract digestibility of starch by steers.

Abstract

Crossbred steers (n = 7; 400 kg BW), fitted with T-type cannulas in the duodenum and ileum, were used to examine the effects of processing method, dry-rolled (DR) vs. steam-flaked (SF) sorghum grain, and degree of processing (flake density; FD) of SF corn (SFC) and SF sorghum (SFS) grain on site and extent of DM, starch, and N digestibilities and to measure extent of microbial N flow to the duodenum. In Exp. 1, diets contained 77% DRS or 77% SFS with FD of 437, 360, and 283 g/L (SF34, SF28, and SF22). In Exp. 2, diets contained 77% SFC with FD of SF34 or SF22. For sorghum and corn diets, respective average daily intakes were as follows: DM, 6.7 and 8.1 kg; starch, 3.8 and 4.7 kg; N, 136 and 149 g. Steers fed SFS vs. DRS increased (P = .01) starch digestibilities (percentage of intake) in the rumen (82 vs. 67%) and total tract (98.9 vs. 96.5%) and decreased digestibilities in the small intestine (16 vs. 28%; P = .01) and large intestine (.5 vs 1.2%; P = .05). As a percentage of starch entering the segment, digestibility was increased (P = .01) within the small intestine (91 vs. 85%) but was not altered within the large intestine by steers fed SFS vs. DRS. Decreasing FD of SFS and of SFC, respectively, linearly increased starch digestibilities (percentage of intake) in the rumen (P = .03, .02) and total tract (P = .03, .09) and linearly diminished starch digestibilities in the small intestine (P = .04, .09). Starch digestibilities (percentage of entry) within the small or large intestine were not changed by FD. The percentage of dietary corn or sorghum starch digested in the large intestine was very small, less than 2% of intake. Microbial N flow to the duodenum was not altered by SFS compared to DRS, or by decreasing FD of SFS and SFC. Reducing FD of SFS, but not of SFC, tended to decrease (P = .07) microbial efficiency linearly and tended to increase (P = .06) total tract N digestibilities linearly. Steam flaking compared to dry rolling of sorghum grain and decreasing FD of SFC and SFS grain consistently increased starch digestibility in the rumen and total tract of growing steers. The greatest total digestibility of dietary starch occurred when the proportion digested in the rumen was maximized and the fraction digested in the small intestine was minimized. These changes in sites of digestion account, in part, for the improved N conservation and greater hepatic output of glucose by steers fed lower FD of SFS reported in our companion papers.

Fontes de energia em suplementos múltiplos para novilhos em pastejo durante o período das águas

“…O processamento de grãos rompe as estruturas dos grânulos de amido e aumentaria sua fermentabilidade ruminal, devido à maior superfície de adesão ao ataque microbiano (Theurer et al, 1999). O grão de sorgo responde melhor que o grão de milho ao processamento (Huntington, 2006).…”

Efeito de fontes e formas de processamento do amido sobre o desempenho e o metabolismo do nitrogênio em vacas Holandesas em lactação

“…Normalmente o processamento do grão tende a reduzir os teores de gordura e proteína do leite (Theurer et al, 1999). Entretanto, neste trabalho, o consumo de MS e a porcentagem de gordura e proteína do leite não diferiram (P>0,05) entre as fontes de amido (Tabela 3).…”

Effects of ractopamine hydrochloride are not confined to mammalian tissue: Evidence for direct effects of ractopamine hydrochloride supplementation on fermentation by ruminal microorganisms1

“…Increasing the concentration of forage tended to increase ruminal pH and decrease molar proportions of butyrate (P < 0.10). Theurer et al [83] examined the impact of grain processing on ruminal digestion in steers fed dry-rolled sorghum or steam-flaked sorghum and found that starch digestion (as a percentage of intake) in the rumen was higher for steers fed steam-flaked sorghum than for steers fed dry-rolled sorghum (82% vs. 67%; P < 0.05). Theurer et al [83] Any compound fed to ruminants can affect the ruminal microbial population and ruminal fermentation, and many feed components have been evaluated for their ability to do so.…”