Dairy cow nutrition – some insights into the future

United Feeds’ CEO Dr Keith Agnew has taken the opportunity of reviewing some of the key nutritional developments that may well have a bearing on the Irish milk sector over the coming years.

Speaking to AgriLand on the final day of the National Ploughing Championships yesterday he reminded dairy farmers that they must commit to meeting the full management and welfare needs of their stock at all times.

“Producing high-quality forages must also be a priority for every dairy farming business, as is the maximising of milk production levels from forage,” he added.

“If this is not being achieved, then the scope to generate profits will be significantly reduced. Ensuring that stock are playing their full role in optimising farm output is also critical. And a key indicator in this context is ensuring that heifers are reared to calve down successfully at 24 months.

“Excessive culling rates are a further indicator that a herd management system is not fit for purpose.”

Turning to the specifics of how new thinking, with regard to nutrition, can continue to improve dairy herd performance, Dr Agnew went on to highlight two broad themes.  The first relates to the use of ‘gas fermentation’ as a means of assessing the effectiveness of TMR-based diets.

“In our own case we have used the technology to try and understand why specific rations have not delivered the level of performance they were formulated to achieve,” he further explained.

“And this can happen. Specific analysis of the forage and concentrate components of the rations will point to there being no problems at all. However, once the TMR is fed, the level of performance can be considerably less than that which had been expected. And in cases where the health of the cows is not the issue, this leaves the impact effect of the ration on the cows’ system as the most probable cause of the problem. One way of getting a handle on how the ration is actually utilised by the animal is through the use of gas fermentation.”

The United Feeds’ CEO has used the services of the Canadian company Fermentrics in this regard.

The analytical procedure carried out requires an individual feed or TMR sample to be placed in a closed vessel with rumen fluid to measure fermentation gas production over a forty eight hour period. Wholly automated, the system collects information on 5,000 occasions during this period. The system can measure Carbon Dioxide, Methane levels and pH values throughout the fermentation process.

From the information made available, a graph is developed from which the carbohydrate digestion rate values are calculated. These values can be used in sophisticated ration-balancing programs rather than relying on book values populating the feed libraries.

The Fermentrics’ technology also allows for direct measurement of microbial biomass production. “All of this information can be used to identify the effectiveness of a specific TMR and what steps can be taken to improve ration formulations in individual farm cases,” stressed Dr Agnew.

“Yes there is a cost to be incurred in having the analysis carried out. But in cases where a significant number of cows are being milked, the benefits to be accrued in successfully tweaking diets in order to improve animal performance will far outweigh this initial outlay.”

Cost

Protein is one of the most expensive constituents in any dairy cow diet. But, as an industry, are we feeding too much of it? This is an issue on which Dr Agnew has some very clear views.

“Over the past number of years, we have assessed the feeding of rations containing reduced levels of protein to dairy cows here in Ireland. This work has been undertaken with a number of milk producers in different parts of the country,” he commented.

“Moreover, we have developed these feeding options across a wide range of management systems and have also taken account of the various forage types and concentrates offered to lactating cows on local farms.”

The trials undertaken by United Feeds have been part of a wider research project involving herds in the US and Canada. The work has been carried out on the basis of feeding these amended diets throughout the entire lactation. All the herds were fed a basal TMR, topped up with nuts fed in parlour or through out-of-parlour feeders.

The work has confirmed that it is possible to maintain, and in some cases increase, milk production on lower protein diets. Individual peak yields of cows tend to be a little lower but cows will have a much flatter milk production curve. Thus, they will produce significantly higher levels of milk during the mid and latter stages of their lactation than their counterparts receiving a standard ration.

Fertility

There is also strong evidence to confirm that cows fed lower levels of protein demonstrate higher levels of fertility performance. This, in turn, will have a major impact on the overall herd profitability. And, of course, as the level of dietary protein is reduced so will be the amount of urea excreted. The objective is to reduce dietary protein levels without impinging on milk output while, at the same time, improving other aspects of animal performance.

“The average total protein in the diets fed to dairy cows in Ireland is in the region 17 per cent and 18 per cent. Research carried out in Europe and North America has indicated that these levels are excessive and that total dietary proteins in the region of 15 per cent are much more in line with a cow’s requirement,” Dr Agnew further explained.

“We have known for years that feeding extra protein to lactating cows will not necessarily increase milk yields. In fact, when this approach is taken increased stress is put on the cow as she has to excrete the additional protein as urea. This, in turn, puts more pressure on her metabolic systems with the result that both potential milk output and fertility levels are reduced.

“The easiest way to reduce overall protein levels in the overall diet fed to cows is to manipulate the formulation of the TMR. And, of course, by taking out protein, this leaves room for other ingredients. For example, we can increase total dietary energy levels.”

Pictured Cows on grass. Photo O’Gorman Photography.

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