Intraruminal chromium controlled release capsules for measuring
herbage intake in ruminants - a review
W.J. Parker, S.T. Morris, D.J. Garrick, G.L. Vincent, S.N.
McCutcheon
Department of Agricultural and Horticultural Systems Management,
Massey University
Proceedings of the New Zealand Society of Animal Production.
1990, 50: 437-442
This paper reviews the application of intraruminal chromium
controlled release capsules (CRC, Captec (NZ) Ltd, Auckland) to the
measurement of herbage intake in ruminants. The capsules are designed
to provide for the linear release of Cr2O3 over c. 25 days in sheep and
c. 20 days in cattle. Uniform release of Cr2O3 is achieved 2 to 3 days
after oral administration of the CRC but steady state levels of Cr2O3 in
the faeces are usually not achieved until day 7 or 8 in sheep and day 5
or 6 in cattle. Where cross-over or multiple feeding level experimental
designs are applied, time should be allowed for Cr2O3 to adjust to a new
steady state in the faeces before sampling for each new treatment. The
period of time required varies from 3 to more than 5 days depending on
the size of feed intake change. The continuous mode of marker release
in the rumen reduces diurnal variation of Cr2O3 in the faeces and this
allows rectal sampling regimens to be applied at different times of each
sampling day. Sward sampling of faeces reduced disturbance of animal
grazing to a minimal level since Cr2O3 is delivered by a single CRC
application. The effects of level of feed intake and feed type on the
rate of Cr2O3 release are usually small, but release rates may be up to
13% lower in rumen-fistulated than in non-fistulated animals and may
differ for capsules of the same time applied to different ruminant
species. Reduced animal handling, flexible faecal sampling times and
lower labour requirements with CRC technology, compared to daily
drenching of Cr2O3, enable the number of experimental animals to be
increased. This improves the likelihood of detecting differences in
mean intake between groups. Intakes of individual animals will not be
reliably estimated with chromic oxide CRC until the digestibility of
herbage consumed by individual animals can be measured more accurately.
Keywords: NZSAPAB;
Ruminants; herbage intake; chromic oxide; controlled release
capsule; methodology
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Last Updated 25-01-1997
