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Quality Meat Production from Beef Cattle During Winter Finishing.
Moloney, Aidan P
Moloney, Aidan P
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2000-12-01
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Moloney, A.P., Quality Meat Production from Beef Cattle During Winter Finishing, End of Project Reports, Teagasc, 2000.
Abstract
A series of experiments were carried out to examine the performance
of the UK metabolisable energy (ME)/metabolisable protein
(MP) system in an Irish context, and to determine the
response in lean tissue growth to changes in the form of nutrients
available for absorption from the intestine.
In Experiment 1, the response of finishing continental heifers to
an increase in MP supply was examined. It was demonstrated that
this type of animal responded positively to an increase in MP supply
in excess of requirements as presently estimated by the UK ME/MP
system. Such an anomaly requires clarification.
In Experiment 2, growth, digestibility and nitrogen retention in
finishing continental steers offered ad libitum, concentrates based on
barley and soyabean or on a mixture of industrial by-products
were examined. The observed higher nitrogen retention in animals
offered the by-product based ration suggested that there is
opportunity to increase carcass protein content by judicious choice
of feed ingredients. This suggestion was explored in Experiment 3.
In Experiment 3, nitrogen retention and carcass composition
were measured in sheep offered rations which resulted in different
patterns of volatile fatty acid supply from the rumen. Nitrogen
retention and the growth of carcass lean tissue were increased by
the inclusion of sodium propionate in a starch-based ration but not
in a fibre-based ration. The apparently contradictory effects of an
increase in propionate supply by dietary means (starch vs fibrebased
rations) or by addition of a salt of propionic acid suggests
that the pattern, as well as the total supply of propionate is physiologically
important in the growing ruminant. The endocrine mechanism
of changes in carcass composition was also explored in this
experiment. Differences in plasma concentrations of hormones
which play a major role in the partition of absorbed nutrients
towards muscle or adipose tissue suggests a role for the endocrine
system in the regulation of growth, independent of energy intake. In Experiment 4, the effect of starch form and concentration (a
dietary means of increasing propionate supply) in high concentrate
rations on growth, efficiency and estimated lean content was examined
in Friesian bulls. Supporting mechanistic measurements were
made in Friesian steers fed the corresponding experimental rations.
For optimum growth, ground starch should not exceed 210 g/kg of
the ration. When included at approximately 300 g/kg, ground
rather than rolled starch had a negative impact on growth. Coarse
rations containing 300g or 480g starch/kg resulted in similar growth
and efficiency. An increase in ground but not rolled starch concentration
decreased the insulin response to a glucose challenge.