Modeling Ruminal Digestibility of Carbohydrates and Microbial Protein Flow to the Duodenum

Abstract

Carbohydrates are the major source of energy for dairy cows and for microbial protein synthesis in the rumen. The prediction of ruminal carbohydrate digestibility and of the flow of microbial protein to the small intestine is difficult because of the variability among various feeds in the kinetics of digestion and passage of neutral detergent fiber and starch. Disappearance of fiber and starch in vitro or in situ and gas production in vitro have been extensively evaluated, improved, and reviewed. Similarly, markers and models to measure ruminal passage rate have been extensively researched and improved. Sources of variation and decreased accuracy for these techniques are discussed. Variation and potential errors also remain for the prediction of microbial protein flow to the duodenum using in vivo procedures. However, when in vivo results were accumulated into a database, microbial N flow to the duodenum over a wide range of conditions could be predicted accurately by intake of net energy for lactation or by dry matter intake and percentage of neutral detergent fiber in the diet. Although evaluation of feeding interactions and specific dietary limitations for microbial protein production in the rumen are possible with some models but not with this regression approach, mechanistic models need further validation and more accurate rate constants for improved accuracy over a wide range of conditions.

Cana-de-açúcar tratada com óxido de cálcio fornecida com diferentes níveis de concentrado para novilhas de corte em confinamento

“…De fato, segundo Firkins et al (1998), o fluxo de Nmic pode ser influenciado, além do nível de concentrado, pelo percentual de FDN, que afeta o pH ruminal, ou pelo suprimento de proteína degradável no rúmen.…”

Effect of corn silage particle size and level of soybean oil on ruminal mat composition, distribution and consistency in Zel sheep

“…So, nonescapable rumen pool sizes were higher in coarse silage diets at 3 h after feeding (p<0.0502). In fact, rumen mat acts as a filter for small particles (Firkins et al, 1998). Increasing the rumen mat at 3 h after feeding, the coarse corn silage diets reduced solids passage in the rumen (p<0.1033); in contrast, escapable rumen pool sizes were higher in fine corn silage diets (p<0.0502).…”

“…Fiber components covered with fat prevent access to rumen microorganisms (Smith, 2000), decrease microbial attachment to fiber particles (biofilm is not formed), reduce fiber breakdown and fermentation (Jordan et al, 2006), and prevent reduction of particle size and particle passage from the rumen, making feed intake to diminish (Onetti and Grummer, 2004;Jenkins et al, 1998). These fat effects cause functional specific gravity, which is the most important factor affecting removal of particles from the rumen; they also cause less increase (Firkins et al, 1998), which prevents the passage of digested particles from the rumen (Jordan et al, 2006). Therefore, this research was designed to investigate the effects of two corn silage particles size and two levels of soybean oil consumption on intake and DM, OM, NDF, crude protein (CP), non-fibrous carbohydrate (NFC) and EE digestion, ruminal mat composition, distribution and consistency and chewing activity in sheep.…”

Níveis de uréia na ração de novilhos de quatro grupos genéticos: estimativa da produção de proteína microbiana por meio dos derivados de purinas na urina utilizando duas metodologias de coleta

“…O fato de a maior parte do nitrogênio que chega ao intestino delgado ser de origem microbiana atesta que a eficiência de crescimento microbiano tem considerável impacto na nutrição de ruminantes (Russell et al, 1992;Firkins et al, 1998). Ainda considerando que a proteína microbiana é de alta qualidade, torna-se importante maximizar sua síntese ruminal (Blümmel & Lebzien, 2001).…”