Ytterbium acetate as a particulate-phase digesta-flow marker

Abstract

I . The ability of ytterbium acetabe (Yb acetate) to fulfil the requirements of a particulate-phase digesta-flow marker in a dual-phase marker system, and of the indigestible acid-detergent-fibre fraction of the feed (IADF) to act as a digesta flow marker, were examined using six mature wether sheep given a diet of dried grass (1 kg dry matter (DM)/d).2. CrEDTA was continuously infused (240 mg chromium/d) into the rumen of all sheep and Yb acetate was also continuously infused (100 mg Yb/d) into the rumen of three of the sheep. At this level of infusion the equilibrium concentration of Yb in rumen, duodenal and ileal digesta and in faeces could be reliably measured by atomic absorption spectrometry. 3.Estimates of faecal DM excretion based on either Yb or IADF did not differ (P > 0.05) from that determined by total collection, whereas estimates based on Cr were significantly (P < 0.05) lower. Urinary excretion accounted for 3.1 % of the infused Cr but no Yb was detected in urine. Estimates of ileal DM flow, assuming total marker recovery, were similar (P > 0.05) with all three markers, whereas the estimate of duodenal DM flow based on IADF was lower (P < 0.05) than the estimates based on either Cr or Yb.4. Compared with the infusion of Cr alone, the infusion of Cr and Yb had no effect (P > 0.05) on nutrient flows at the duodenum, ileum and in faeces nor on microbial degradative activity, volatile fatty acid production and N metabolism in the rumen. 5. Polyester bag and in vitro studies showed that pre-labelling the dried grass with up to 285 mg Yb/g DM did not affect its susceptibility to microbial degradation.6. The Yb in rumen, duodenal and ileal digesta was predominantly (> 90%) associated with the particulate matter but was not uniformly distributed and its concentration increased as particle size decreased.7. The use of CrEDTA and Yb acetate as a dual-phase marker system proved more reliable in estimating 'true' duodenal flow than the use of the individual markers when the digesta sample was unrepresentative.Net absorption from or secretion into the different parts of the gastrointestinal tract can be determined by measuring the quantity and composition of digesta flowing past cannulas inserted at various points along the tract (MacRae, 1975). To avoid the problems associated with total digesta collection, estimates of flow are usually obtained from the relation between the equilibrium concentration of a marker in a sample of the digesta and the amount of marker continuously infused or ingested. When re-entrant cannulas are used in conjunction with automatic sampling machines (Canaway & Thomson, 1977), which allow continuous sampling and so provide a representative sample of the total digesta flow, only one marker is required. However, because digesta flow from the rumen is a discontinuous process with the fluid and particulate phases flowing at different rates, the use of a single marker with spot sampling from either re-entrant cannulas or simple ' T'-shaped cannulas may give erroneous estimates of flow, ...

Supplementing lactating dairy cows with a vitamin B12 precursor, 5,6-dimethylbenzimidazole, increases the apparent ruminal synthesis of vitamin B12

“…Cows were Omasal sampling and analyses Spot samples of omasal digesta leaving the rumen were collected through the reticulo-omasal orifice from the eight ruminally cannulated cows using the omasal sampling technique developed by Huhtanen et al (1997) and Ahvenjärvi et al (2000), as adapted by Reynal et al (2003). The following omasal digesta markers were used: indigestible NDF (Huhtanen et al, 1994) for the large particle phase (LP), YbCl 3 (modified from Siddons et al, 1985) for the small particle phase (SP) and Cr-EDTA (Udén et al, 1980) for the fluid phase (FP). A marker solution containing YbCl 3 , Cr-EDTA and 15 NH 4 SO 4 with 10 atom percentage excess 15 N (Isotec, Miamisburg, OH, USA) as a bacterial marker was prepared as described by Reynal and Broderick (2005).…”

The effect of dietary carbohydrate composition on apparent total tract digestibility, feed mean retention time, nitrogen and water balance in horses

“…Faecal samples for passage rate measurements were dried at 60°C for 48 h and ground to pass a 1 mm screen. Samples of 500 mg were incinerated at 550°C for 16 h and Yb was analyzed with the procedure described by Siddons et al (1985).…”

Predicting the profile of nutrients available for absorption: from nutrient requirement to animal response and environmental impact

“…For external markers of particle passage, it is assumed that they represent the passage behaviour of the particles ingested with the diet. However, applicability of the results have been criticised because external markers may restrict the digestibility of the particles they are linked to, they may bind preferentially to small particles, and they may migrate to rumen fluid (Uden et al, 1980;Siddons et al, 1985;Combs et al, 1992). The inert internal markers referred to earlier, circumvent these problems as they form intrinsic components of the feed particles.…”