There are some other important factors to consider when compiling a phosphorus supplementation plan for northern beef herds.

Cropping. Phosphorus deficiency can occur in places where it’s not expected to be a problem. Cereal cropping, especially when not accompanied by appropriate fertiliser application, has caused soil nutrient rundown in some regions. In these situations, cattle performance may be improved with phosphorus supplements. A serum phosphorus test is the best way to diagnose the problem.

Assessment of individual paddocks. Where marked soil variation occurs within properties, it’s recommended to assess every major paddock when developing a comprehensive P supplementation program for the enterprise. If the assessment is performed on young grower or breeder cattle that have not received P supplement for at least two weeks prior to sampling and are on a positive plane of nutrition, this will most likely be a ‘one-off’ test unless phosphorus fertiliser is being applied.

Botulism. Phosphorus supplementation does not reduce the need to vaccinate against botulism. It will reduce the risk by avoiding the bone-chewing behavior that can lead to botulism.

Cost of supplementation. The cost benefits will vary depending on the level of deficiency being encountered. A 2018 trial in the NT suggested a cost of around $20/head/year to provide adequate phosphorus for breeders, although cost varies depending on the current price of phosphorus. Other costs such as distribution, freight and storage costs will change between properties and this also needs to be factored into the economic assessment. In this trial, the benefits of supplementation outweighed the cost. Benefits included: 

  • 30kg increase in annual heifer growth rates
  • >30kg increase in weaner weights
  • >100kg increase in breeder cow weights
  • at least a 7% reduction in mortality rates
  • at least a 30% increase in re-conception rates.

Conduct your own cost-benefit analysis depending on the severity of the deficiency in your pastures.

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