Digesta characteristics of dorsal, middle and ventral rumen of cows fed with different hay qualities and concentrate levels

Abstract

The influence of fibre content of hay (H) and concentrate level (C) on local differences in the composition of ruminal digesta (ratio of solid to fluid digesta, DM, NDF, ADF and ADL content), particle size (MPL), specific gravity (SG) and fermentation (pH and concentrations of SCFA and bicarbonate) have been tested on two ruminally cannulated Friesian cows (520 kg BW) which were fed restricted, using individual cows as experimental units. Digesta samples were collected via cannula from three rumen layers: 5 to 10 cm (top) and 25-35 cm beneath the top of the particle mat (middle) and 5-10 cm above the rumen floor (bottom). For a main plot treatment (H x C), repeated samples were collected at four time intervals (1 h before and 2, 5 and 10 h after morning feeding) on each of two days. From top to bottom rumen the share of solid digesta mass (SM), DM and NDF contents of squeezed digesta fluid (SRF) and concentration of SCFA decreased (P < 0.05); pH and bicarbonate concentration increased (P < 0.05), while DM, NDF, ADF and ADL contents in SM, MPL and SG did not differ. Higher NDF content of hay (from 47-62%) increased SM, fibre fractions in SM, MPL, pH and concentration of bicarbonate in ruminal digesta, especially when 50% concentrate was given, while SG decreased. When the concentrate level was enhanced from 20 to 50%, digesta SM, MPL and the content of DM and NDF in SRF increased, while pH, concentrations of SCFA and acetate decreased when low-fibre hay was given. With longer time after feeding the digesta SM was reduced and fibre content in SM increased. The increase of the fibre content of hay reduced the possible negative effect of high concentrate level on the stratification of ruminal digesta. The decrease of the fibre content of hay promised better conditions for fibre digestion in the rumen when concentrate availability is limited.

Simultaneous Estimation of the pH of Rumen and Reticulum Fluids of Cows Using a Radio-Transmission pH-Measurement System

“…The rumen pH varies considerably with the site where the sample is collected [6,25]. Tafaj et al [25] collected digesta samples from three layers of the rumen digesta; the top and middle were from 5-10 and 25-35 cm below the ruminal mat surface, respectively, and the bottom sample was 5-10 cm above the rumen bottom.…”

“…Repeated collections of rumen fluid are needed to measure pH, which can lead to peritonitis following rumenocentesis with a trocar and esophageal injuries induced by oro-ruminal probe suction. Moreover, the reliability of the rumen pH likely depend on the operator's skill, the sampling site (bottom vs. middle of the rumen and rumen vs. reticulum), and sampling procedure (rumenocentesis vs. an oro-ruminal probe) [3,6,9,17,25]. An indwelling wire system has been used to measure the pH at the bottom of the rumen [2,18,19,22,23], but there are no reports on simultaneous pH measurements of fluids at the bottom and in the middle of the rumen and in the reticulum (i.e., three sites) of cows.…”

“…Tafaj et al [25] collected digesta samples from three layers of the rumen digesta; the top and middle were from 5-10 and 25-35 cm below the ruminal mat surface, respectively, and the bottom sample was 5-10 cm above the rumen bottom. They reported that the higher concentration of VFA and lower pH in the dorsal rumen reflected higher fermentation activity in the solid digesta.…”

Aspects of rumen adaptation in dairy cattle : morphological, functional, and gene expression changes of the rumen papillae and changes of the rumen microbiota during the transition period

“…The fluid in the ventral rumen is likely more readily mixed than the fluid in the dorsal regions of the rumen due to the absence of the rumen mat. This allows for a more rapid equilibration of VFA concentration in the rumen fluid aiding VFA absorption (Tafaj et al, 2004;. The formation of the rumen mat is considered essential for optimal rumen functioning .…”

“…The formation of the rumen mat is considered essential for optimal rumen functioning . Ration composition, feed particle size, and fiber content affect the stratification of feed in the rumen and mat formation (Tafaj et al, 2004;. In the rumen mat, VFA concentration is generally higher, and pH lower, than the fluid in the ventral rumen .…”