Care needed when reducing phosphorus levels in broiler diets

A global shortage of feed phosphate has forced producers to review dietary levels. But care is needed when making changes, as Aviagen's Anthony Waller explains.

Suppliers of feed phosphates announced around Christmas 2007 that supplies of phosphates would be insufficient to meet orders from the animal feed industry. In some cases only 30% of ordered tonnage was supplied.

This had a serious impact upon poultry feed manufacturers and producers, in terms of ability to supply stock with required levels of phosphorus and the cost of phosphorus in the diet. While the initial crisis has subsided, concern over phosphate supply and cost going forward remains.

The shortage is a result of exceptionally high demand for phosphorus-containing fertilisers. Feed phosphates and fertilisers are both produced from a common raw material - phosphoric acid - and extra fertiliser production has resulted in a shortage of it for feed phosphate production.

Higher fertiliser demand has resulted from increased global plantings of cereals and protein crops in response to tight global stocks and subsequent soaring feed prices.

So what are the implications for poultry production? There are two key effects: First, there is the difficulty in meeting the phosphorus requirements of birds and, second, it has increased the cost of feed.

This puts further pressure on feed formulation, as nutritionists look to maximise stocks of feed phosphates, while keeping formulation cost down. Nutritionists will attempt to conserve feed phosphate stocks by reducing levels in feeds and using alternative ingredients.

But these attempts could have implications on production and it is worth considering how best it should be managed.

Reducing levels in feed

Any reduction in phosphorus below recommended levels must be carefully managed. If reducing phosphorus, several factors should be considered.

Broiler starter formulations should be left unchanged. Phosphorus levels are crucial for skeletal development and growth, and any changes in specifications at this time can have serious implications for welfare and performance.

If reducing the phosphorus levels of broiler feeds, then first consider the final withdrawal of feed, and work backwards towards the grower diet. This approach involves least risk of negatively affecting bird welfare and performance. In terms of volume used, the increasing feed intake of broilers during the latter phase of the grow-out cycle will result in a significant reduction in added phosphate use.

When setting a minimum specification level, bear in mind that broilers show deficiency symptoms at levels of available P of 0.29% of total diet (as is). Also take into account other factors that may increase phosphorus requirements, such as disease exposure, toxin levels in feed and susceptibility to rickets.

Any reduction in phosphorus will alter the calcium-to-available-phosphorus ratio. Calcium levels should be adjusted to keep this at 2:1 to maintain good bone health.

It is worth checking the specification levels of other nutrients which affect bone mineralisation calcium, magnesium, manganese and vitamin D3.

Formulating to digestible phosphorus can potentially reduce the volume of mineral phosphate required in the feed while maintaining correct formulation. But if doing this, great care must be taken to ensure that raw material values are amended.

Lastly, breeder formulation specifications should only be considered if absolutely necessary. Low phosphorus levels will compromise eggshell quality, hatchability and progeny viability.

Alternative ingredient strategies

There may be a benefit in using phytase enzymes. But, again, a number of factors should be considered before embarking on their use.

If adding phytase to diets that have previously not included phytase, check with the supplier that the raw material and feed specification values used in ration calculations are correct. Also check correct values have been used for phosphorus, calcium, sodium and other minerals.

Feeds already containing phytase may benefit from an increased dosage of the enzyme, both in terms of phosphate sparing and cost saving. Consult the supplier as to the best way to achieve maximum benefit and ensure the mineral content of the feed is kept in balance.

When using phytase in breeder feeds, it is particularly important that the raw material and specification levels are managed to keep mineral content balanced, particularly the calcium-to-phosphorus ratio.

Alternative sources of mineral phosphates may be available, but the phosphorus and calcium contribution may not be the same as for the more traditional phosphates, both in terms of absolute level and availability. Quality should be consistent, to be certain that the correct level of minerals will be supplied to the birds.

And lastly, watch out for heavy metal contamination in mineral phosphates offered.

So to conclude whatever changes you make, we recommend a proactive approach by monitoring for any changes. Implement a monitoring scheme by health experts or production staff checking young broilers for bone formation and signs of mineral deficiency-related complications. Monitor eggshell quality and productivity and ensure feed intake is optimised so mineral intake is adequate.

Key pointers

* Focus on withdrawal and finisher feeds
* Exercise caution with broiler breeder feeds
* Maintain calcium:phosphorus ratios
* Review raw material mineral values
* Take advice on phytase use
* Be cautious in the use of alternative materials
* Be proactive – monitor bird performance

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Care needed when reducing phosphorus levels in broiler diets