Optimising protein use of high production dairy cattle

It is estimated that by 2020, the annual demand for milk and dairy products in the developing countries will stand at 391 million tonnes. This will be more than double the dairy product needs of 168 million tonnes recorded in 1998.
The rise in demand is attributed to the growth of the middle class in the population of East Africa, which has resulted in the greater need for livestock-derived food products such as milk, meat and eggs.
Faced with a limited land size to expand livestock rearing, this demand has to be met by improved productivity, which largely hinges on efficient use of feeds.
Feeds remain a key driver in the dairy production value chain as they determine the productivity and consequently profitability of dairy businesses.
In addition, feed is useful in the application of new innovations and modern technology. In dairy nutrition, protein is one of the major limiting needs in the diets of lactating cows. This is particularly the case for cows in early lactation when the dry matter (DM) intake is relatively low and the protein requirement is high.
In East Africa, some of the protein sources used for dairy feed, include cotton seed cake, sunflower meal, sunflower cake, soya bean meal, full fat soya, alfalfa, copra, and fish meal. These ingredients are expensive, seasonal and scarce, yet the nutritionist is expected to use them to formulate feed that will enable high milk production at the lowest cost possible.
For many years, dairy nutritionists have been looking at common parameters such as energy, starch, fibre, crude protein, minerals and vitamins. However, no account is taken of such factors as ingredient availability, rising cost of protein sources or how protein degradation takes place in the rumen.
A majority of dairy nutritionists will formulate their diets based on crude protein, usually between 17 and 18 per cent, for high yielding dairy cattle. To achieve this, the nutritionist is forced to use more of the above mentioned ingredients, resulting in expensive dairy feeds.
Reduced fertility A diet containing high protein is not a satisfactory solution to meeting a high producing dairy cow’s nutritional requirement because the breakdown of dietary protein in the rumen is one of the most inefficient processes.
As a matter of fact, animals do not have a requirement for protein. Instead, they require specific amino acids that are the building blocks that make up proteins. Crude protein is, therefore, a parameter that blinds our eyes and does not allow the dairy industry to progress.
Research has confirmed that elevated crude protein levels in the diet will result in high levels of urea nitrogen in blood, which is associated with reduced fertility in lactating dairy cows.
Ruminants obtain amino acids from microbial protein. Rumen microbial protein supplies over half of the amino acids absorbed by ruminants. It is a relatively wellbalanced protein source that has an essential amino acid profile similar to what cattle require for growth and milk production. But rumen microbial protein synthesis cannot supply sufficient quantities of amino acids to meet the requirements of cows producing large quantities of milk.
Milk production The importance of optimising the supply of amino acids to improve protein utilisation, increase milk production and milk solids is an industry game changer in a highly competitive market.
Supplementing dairy rations with rumen-protected amino acids that are limiting milk production and milk protein synthesis may compensate for metabolisable protein deficiency in dairy cow rations. It is accepted that methionine and lysine are most often the first limiting amino acids for milk production.
The benefits of amino acid balancing in dairy cattle are clear and include improved dairy performance, and fertility, reduced impact of dairy production on environment and overall profitability. Methionine is the first limiting amino acid in milk production. To meet methionine requirement, a ration for a high producing dairy cow either needs to be high in its crude protein content, which is expensive or to be supplemented with DL-Methionine that has been found to be more cost effective.

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