The flow of forage particles and solutes through segments of the digestive tracts of cattle

Abstract

An experiment was conducted to investigate the compartmental mean residence time, (CMRT) of feed residues in segments of gastrointestinal digesta of mature Holstein steers. The objective was to evaluate assumptions that feed residues flow through ruminal digesta as sequential mixing pools having age-dependent (GN) and age-independent (G1) distributed residence times respectively (GN → G1 flow). The basal diet was a semi-tropical hay containing 98 g crude protein and 503 g apparently digestible DM per kg DM. The hay was consumed and feed residues of different size and/or previous digestion from the hay were inserted into the reticulo-rumen (rumen) and abomasum. Marker profiles appearing at the duodenum and faeces were fitted to various compartment models to estimate CMRT. Post-abomasal CMRT did not differ among solutes or feed residues of different size and previous digestion and constituted only 5⋅8 % of the CMRT for the entire gastrointestinal tract. Markers initially applied to orally or ruminally dosed feed residues exhibited profiles in duodenal digesta and faeces conforming to GN → G1 flow. Previously undigested, masticated feed residues inserted into the dorsal rumen digesta had longer ruminal CMRT in the GN pool but not the G1 pool than did similarly inserted faecal small particles or normally ingested hay. These results support model assumptions of GN → G1 flow within rumen digesta. The results support mechanisms proposed for the GN pool as the 'lagrumination pool' and the G1 pool as the 'mass action turnover pool'. If further validated, rumen CMRT in cattle could be estimated from marker profiles in more easily obtained faeces to estimate ruminal CMRT required for feed evaluation systems. Compartmental models: Digesta flow: Forage particle sizeThe compartmental mean residence time (CMRT) of feed residues in the digesta of the reticulo-rumen (rumen) is determined by various forces that constrain and propel ruminal escape of undigested feed residues. A major force constraining escape is the competition among ingested feed residues with resident residues of previous meals as the result of the continual mixing of ruminal digesta. If this competition for escape is passive for all feed residues, regardless of their attributes or age in the pool, then CMRT is a function of the mass of resident feed residues and the continued intake rate of feed residues, i.e. mass action dilution turnover rate of the continued intake. Matis (1972) observed that newly ingested feed residues require ageing before acquiring properties required for escape, properties such as particle size reduction for example. Matis (1972) proposed an age-dependent distribution of residence times to model this initial process constraining escape in contrast to an age-independent, mass action turnover. The age-dependent turnover of undigested feed residues in ruminal digesta could be modelled as a single agedependent mixing pool or a sequence of age-dependent → age-independent mixing pools. Ellis et al. (1991Ellis et al. ( , 1994 proposed the 'un-...

Effect of fibrolytic enzymes added to a Andropogon gayanus grass silage-concentrate diet on rumen fermentation in batch cultures and the artificial rumen (Rusitec)

“…Short-term, rather than long-term (e.g., 48 h), incubations have been used to assess the effect of fibrolytic enzymes, because long-term incubations are not representative of the residence time of fibre in the rumen of high producing dairy cows (Colombatto et al, 2003b;Eun and Beauchemin, 2007). However, in beef cattle fed high tropical forage (C 4 ) diets (Wylie et al, 2000), ruminal residence times can be substantially longer, possibly making a longer incubation period (48 h) more relevant to studying responses to EFE. In the present study, the DM disappearance of the FS diet after 48 h of incubation was increased with EFE application.…”

The effect of soya protein supplement enriched with three amino acids on duodenal flow of soluble nitrogen fractions and amino acids in dairy cows

“…Smartamine M producer reports release of 90% of Met after 2 h incubation in pH 2 buffer. However retention time of feed particles in abomasum can be shorter (Wylie et al, 2000) and that is why part of tablets could escape disintegration in abomasum. Retention time of large and heavy particles is shorter than that of digesta and shape of their passage curve is a narrow peak (Třináctý et al, 2005).…”

A comparison of parameters of the passage of nylon capsules and digesta calculated from faecal excretion data obtained in lactating cows

“…The estimated CMRTS values for nylon capsules and labelled silage were 20.1 and 37.2 hours (P < 0.01), respectively. Assuming that in particular CMRTS represents the time of retention in the reticulo-rumen (Wylie et al, 2000), we can state that Cr-labelled particles remained there for a longer period of time than the nylon capsules. It can likely be explained by the high specific gravity of the nylon capsules (Třináctý et al, 2003).…”

“…Campling and Freer (1962), Ehle and Stern (1986) and Kaske and Engelhardt (1990) stated that the passage of larger particles of higher specific gravity through the intestines was slower. Wylie et al (2000) found out that the retention time of ingested and masticated hay in the intestines (measured by a direct method in cannulated animals) accounted for 74.4% and 94.9% of τ value (calculated from faecal samples), respectively. Using the data published by Mambrini and Peyraud (1997) we could calculate that the corresponding values were 75.8% (feeding hay) and 84.8% (ground hay).…”

“…According to Wylie et al (2000), due to a mixing flow in the forestomach digesta CMRTS amounted to 94.2% of that for the entire gastrointestinal tract. From the results of the detailed compartmental analysis mentioned above it stands to reason that the shorter mean retention time of nylon capsules in the reticulo-rumen (CMRTS) was caused in particular by the short CMRT2 (descending part of the passage curve), thus by the high outflow rate (k) of nylon capsules from the reticulo-rumen (see different faecal excretion patterns of nylon capsules and Cr-labelled silage in Figure 1.…”