To make
systematic rather than empirical improvements in increasing the efficiency, we
need to adequately define the requirements of the high yielding dairy cow and
to match them with a corresponding supply. Because the supply of protein to the
dairy cow differs in the composition of its building blocks, the amino acids,
and because the metabolic fates of amino acids are not fixed, it is therefore
important to consider individual amino acids to better balance dairy rations,
says Hélène Lapierre
Methionine should be added to cow diets to restore
amino acid balance and optimise lactation performance. However, it must be
supplied in a form which protects it from the micro organisms in the rumen. A
new chemical derivative of methionine has been developed, which provides
bioavailable methionine and activates fermentation by the rumen at the same
time.
The term bypass has become widely used to describe treatments which
allow nutrients, especially proteins, to pass largely unchanged through
the rumen for digestion in the omasum or abomasum.
How well do we understand protein
nutrition? Research has led us a long way towards a full understanding of the
mechanisms of digestion and absorption of proteins and amino acids, but the
true value of specific intestinal transport molecules for small peptides is not
as well recognised.
A variety
of feed additives and feed ingredients, some with excellent nutritional
properties, have become questionable. What are the advantages and disadvantages
of these doubtful ingredients and what are the alternatives?
As the BSE
hysteria calms, some of the quieter voices are still audible. These are
offering alternative explanations for the cause of the epidemic. Though
research is still in its infancy, Czech
scientist Dr Josef Hlásny firmly believes that scrapie-infected MBM was not the
sole culprit.
Many trials have shown that the protein source in the diet of the dairy cow
could have a marked influence on milk protein secretion. In practical
ration formulation it is almost impossible to meet both the lysine and
methionine constraints for high milk production (also meat production in beef
animals and sheep) respectively from conventional raw materials
alone.
Grazing is
a valuable, low cost resource for feeding high-yielding dairy cows. However,
the balance between providing sufficient energy and managing grassland is
delicate. Full exploitation of grazing systems to maximise milk yield requires
that concentrate feeding is also optimised.
The rumen
is a highly evolved and adaptable fermentation system for breaking down
otherwise indigestible plant materials. Yet many scientists are seeking to
develop proteins which bypass rumen digestion altogether in order to increase
productivity.
Nutrient synchrony (or the distribution of nutrients within a day) affects
protein, glucose and fat metabolism and can ultimately impact on the utilization
of nutrients in preruminant calves, concludes PhD student Joost van den Borne at
Wageningen University in the Netherlands.