Cr-mordanted Fibre Research Articles

Retention of Cr-labelled grass hay and silage in different segments of the gastrointestinal tract of dairy cows

Two experiments were conducted to study solids retention in different segments of the digestive tract of dairy cows. In Exp. 1 three lactating cows with rumen and duodenal cannulae were fed grass silage and lib, and 0, 3 or 6 kg of concentrates per day in a Latin square design. Retention in the total tract (MRT tot), stomachs (MRT st) and, by difference, intestines (MRT int), was measured from the changes in Cr concentration in duodenal and faecal samples after a single dose of Cr-mordanted fibre in the rumen. A 3-pool kinetics model with lag was fitted to the data. In Exp. 2, 3 lactating and 2 dry rumen cannulated cows were used. The lactating cows were fed hay, fresh grass and concentrates at 16–17 kg DM/d and the dry cows were fed 8.0 kg hay alone. Hay and faeces were Cr-mordanted and given as a pulse dose in the rumen or through the reticulo-omasal canal, respectively. Retention in total tract, post-rumen (MRT pt ) and by difference, rumen-reticulum (MRT L ), was calculated as in Exp. 1. The silage based diets in Exp. 1 tended to give higher MRT tot than the hay and grass diets in Exp. 2 but the decrease in retention time with intake was also more marked. A very small effect of intake on MRT int and MRT pr, was seen in both experiments. Lag as a proportion of MRT for individual parts of the gastrointestinal tract was used as an indicator of incomplete mixing. The proportion decreased in the order of intestines > post-rumen > stomachs > rumen. The proportion of MRT st (Exp. 1) and MRT r (Exp. 2) in MRT tot was 0.88 and 0.67, respectively. Retention in the rumen was characterized by both a lag phase and multiple pools.

PARTICULATE AND FLUID PASSAGE STUDIES IN SHEEP FED A HAY-BASED DIET

Cr-mordanted fiber, Cr-impregnated cellulose, 169ytterbium, 51Cr-EDT and PEG were compared as digesta passage rate markers in the stomachs and the whole tract in sheep fed hay (80%) and concentrates (20%). Mean retention times of the particulate markers are in the order Cr-mord. > Cr-cell > 169Yb. Cr-EDTA gives more consistent results than PEG. Key words: Particulate markers, fluid markers, mean retention time, rumen, whole tract, feeding frequency, hay, sheep

A Note on the Effect of Different Feeding Levels on the Rate of Digesta Passage in Rabbits

Abstract A study on digesta passage was made with Cr-mordanted fibre in 28 rabbits. The rabbits were fed a pelleted diet at either restricted or ad lib. level. The restricted rabbits were realimented at the same level of feeding as the continuously ad lib. fed animals. Restricted feeding, 50% or 60% of ad lib., resulted in a mean retention time of 26.1 hours or 19.7 hours respectively, compared with 12.6 hours with ad lib. feeding. At realimentation, when all groups were fed at the same feeding level, mean retention times were nearly identical.

The determination of digesta particle size in some herbivores

Methods for determining and describing digesta and faecal particle size were studied. Higher mean particle size values were demonstrated for wet sieving as compared to dry sieving. Equines had larger faecal particle size than ruminants and rabbits. Particle size decreased with body weight in rumen-reticulum and facese for the ruminants. The fibre particle size was the same in rabbit hard and soft faeces and similar to sheep and goat faeces. The excretion pattern of Cr-mordanted fibre in sheep was shown to be influenced by the fraction that was labelled in the rumen. Retention time in the rumen and whole tract increased with increasing particle size. In rabbits, <75 μ or > 300 μ Cr-mordanted fibre particles gave similar marker retention times.