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Voluntary consumption of forage by sheep and its relation to the size and shape of particles in the digestive tract

Published online by Cambridge University Press:  02 September 2010

J. E. Troelsen  and
J. B. Campbell
J. E. Troelsen
Affiliation:
Research Station, Canada Department of Agriculture, Swift Current, Saskatchewan, Canada
J. B. Campbell
Affiliation:
Research Station, Canada Department of Agriculture, Swift Current, Saskatchewan, Canada
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Extract

Two alfalfa varieties and four grass species were harvested for hay at several stages of maturity. Each hay was given to sheep to provide measures of voluntary consumption and digestibility. Digesta samples were obtained from the reticulo-rumen, omasum and abomasum by killing the sheep at the end of the feeding periods.

Sieving analyses of the digesta revealed that the fraction retained by a 0·25-mm sieve provided greater differentiation between experimental treatments than those retained by 0·5-, 1·0- or 2·0-mm sieves. The weight percentage of this fraction was used as a measure of the relative particle size despite its profound dependence on size, shape, density and distribution of individual particles.

The variation in relative particle size of digesta from different sheep fed on the same diet was illustrated by coefficients of variation ranging from 4 to 11%. Four replicates, however, were sufficient to detect numerous differences (P<0·05) between experimental treatments.

Omasal digesta from alfalfa hay had a greater relative particle size than those from the grass hays at comparablematuritystages. This may be attributable to an apparently more compact particle shape observed in the alfalfa digesta, assuming that in a simple physical sieving process the most compact particle passing a given opening will have the greatest mass. It was proposed that digesta particle shape may have greater specific importance than relative particle size for the rate of passage and voluntary intake of coarse roughage.

A direct relationship was observed between voluntary feed consumption and the relative particle size of omasal digesta from different grass hays at similar maturity stages. This was the reverse of that observed between different maturity stages within hay species. It was hypothesized that the former relationship was due mainly to changing mass of the individual particles passing the reticulo-omasal opening, whereas the latter relationship was caused mainly by the particle size distribution.

The relationship between the relative particle size of digesta from the reticulo-rumen and that of digesta from the omasum supports the theory that the reticulo-omasal opening is the site of major obstruction for the passage of coarse roughage through the digestive system of ruminants.

Type
Research Article
Information
Animal Production , Volume 10 , Issue 3 , August 1968 , pp. 289 - 296
Copyright
Copyright © British Society of Animal Science 1968

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References

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