Removal of digesta components from the rumen of steers determined by sieving techniques and fluid, particulate and microbial markers

Abstract

1. When 103Ru-labelled Tris (1,lO-phenanthroline) ruthenium I1 chloride (lo3Ru-P) particulate marker in aqueous solution was added to the rumen of four steers given 5.5 kg grass hay/d at two-hourly intervals, the distribution of lo3Ru-P marker among rumen particles of various sizes was the same at 4 h, 3 d and 7 d after administration, the concentration of ln3Ru-P/g dry matter (DM) was inversely related to particle size and 0.30 of the lo3Ru-P was associated with the DM of particles too large to be moved from the rumen at a meaningful rate. Thus, fractional outflow rate (FOR) of lo3Ru-P would reflect, but was not a direct measure of, the FOR of the small particle pool in the rumen.2. When rumen digesta were labelled with ln3Ru-P, placed in nylon cloth bags and incubated in vitro with unlabelled digesta, 59% of the loaRu-P disappeared from the nylon bag in 24 h, and 74% in 48 h. Similar results were obtained when large particles (retained by a 3.2 mm mesh screen during wet sieving) from rumen digesta were subjected to this procedure.3. In a further experiment, the steers were given the hay in either the long or ground form and drinking water to which 10 g sodium chloride/l were, or were not, added.4. The FOR of WrEDTA in centrifuged rumen fluid was increased (P i 0.05) from 1.78 to 2.10/d by grinding of the hay diet, but was not influenced by the intake of an additional 257 g NaCl/d. The FOR values of lo3Ru-P in mixed rumen digesta and organic 35S in micro-organisms were linearly correlated (P < 0.05) and were not affected (P > 0.05) by grinding and salt treatments. On average, the FOR of organic 35S in micro-organisms was 0.41 of that of WrEDTA in centrifuged rumen fluid and 0.85 of that of ln3Ru-P in rumen digesta respectively. 5.Grinding of the hay did not (P > 0.05) change the proportion of rumen DM (0.47W.515) or faecal DM (0.107-0.153) retained by the 3.2 mm mesh and larger screens.6. FOR from the rumen of a given size group of particles was calculated as the ratio, estimated daily flow from the rumen of the size group: rumen pool of the group. With increasing particle size there was a progressive decline in FOR; values of FOR for groups of particles greater than 4.0 mm were negligible. If the rumen DM was considered to behave as two pools, the 3.2 mm mesh screen appeared to be an appropriate division between the large-particle and the small-particle DM pools.7. FOR of lignin present in mixed rumen digesta was 0.48 of the mean of the FOR values of the particle groups of the small-particle pool, while the FOR of lignin present in the small-particle pool was 0.92 of the mean small-particle FOR.

A two-pool model of tritiated water kinetics to predict body composition in unfasted lactating goats

“…Other attempts to correlate GW with any of the pools generated during the fitting of models to D 2 O enrichment curves in ruminants have been less successful, for various reasons. (1984) found GW to be linearly related to findings that this technique overestimated WTO with an R 2 of 0-85, although inclusion rumen water in sheep (Poppi, Minson and of data from both calves and mature cattle Ternouth, 1981) and in steers (Dixon and would ensure high correlations when Milligan, 1985). These cattle were then provided with food and major reasons for the lower correlation water and were not slaughtered until 3 days between GF and CrEDTA space than later, during which time increases in GF between rumen volume and CrEDTA space is would have occurred.…”

Perfil granulométrico da fibra dietética sobre o tempo médio de retenção e a digestibilidade aparente de dietas para vacas leiteiras

“…O maior tempo de permanência foi observado na dieta com maior proporção de partículas mais grosseiras, verificando-se que as partículas da dieta com menor perfil granulométrico permaneceram por tempo menor no trato gastrintestinal. Os resultados são compatíveis com os verificados na literatura (Dixon & Milligan, 1985), que demonstram claramente ser o tamanho da partícula dietética um dos principais fatores a determinar a velocidade de trânsito da digesta no trato gastrintestinal.…”

“…Esta observação é confirmada pelos resultados apresentados neste estudo, no qual as dietas com proporção de partículas de maior tamanho ficaram mais tempo retidas no trato gastrointestinal. Dixon & Milligan (1985) verificaram que a velocidade do fluxo da digesta no trato gastrointestinal de ovinos foi influenciada pelo tamanho e pela densidade da partícula de feno, com o maior tempo de permanência associado às dietas que apresentavam maior tamanho da partícula e menor densidade. O mesmo padrão foi observado por Kaske & Von Engelhardt (1990).…”

Modelagem da redução do tamanho de partículas na alimentação de ruminantes

“…Bruining et al (1998) observaram frações mais altas (entre 11,1 a 14,0%) de matéria fecal retida em peneiras de 1,25 mm. Foram também observados teores em torno 3 a 4 mm para bovinos em crescimento (DIXON & MILLIGAN, 1985). Valores acima de 4 mm (CARDOZA & MERTENS, 1986) e 4.25 mm (WOODFORD & MURPHY, 1988) foram determinados para gado leiteiro.…”