Inside Dairy October-November 2020

feed matters

Photo: Walling Contracting Southland Ltd

Inflating the silage stack Is it worthwhile applying additional nitrogen (N) fertiliser or feeding palm kernel expeller (PKE) to inflate spring surpluses? DairyNZ’s Kieran McCahon explores some potential costs and considerations.

After a challenging summer, many farmers have reflected on the value of homegrown silage to help meet animal demands and manage the Fat Evaluation Index (FEI) during feed deficits. This has reignited questions of whether there’s value in using urea or imported feed to inflate pasture surpluses during spring to harvest a greater quantity of pasture silage. Cost comparison: urea vs PKE Actual costs will vary between farms, depending on factors such as pasture management, wastage losses and how the silage is made (e.g. pit vs bale). N-boosted pit silage may cost around 30c/kg DM, or 2.7c/ MJ ME. This assumes a urea price of $700/t applied ($1.52/kg N), a response rate of 10kg DM/kg N, and harvesting costs of 12c/kg DM, and accounts for wastage losses during harvesting and ensiling. High rates of N already applied during spring will reduce the potential pasture growth response to additional N, and increase this cost per kg DM. Given impending limits on N use, carefully consider where the greatest value from N could be gained within your system. In comparison, at a PKE price of $280/t landed, feeding PKE to create silage may cost between 40 to 60c/kg DM or 3.6 to 5.5c/ MJ ME, after accounting for wastage during feeding, feed-out costs (e.g. fuel, repairs, maintenance and depreciation) and further wastage during harvesting and ensiling. Provided a good response to N can be achieved, at current market prices, N-boosted pasture is likely to be a more cost- effective approach. The cost of PKE would need to be below $240/t landed, with very good management, to generate silage at a comparable cost. Considerations These costs above should be assessed within your farm system, given your own attitude to risk on:

• market prices (milk, urea, PKE) • frequency and severity of summer feed deficits, and related contingency plans • cost of alternatives (e.g. reducing animal demand or the lowest cost alternative supplement to PKE) • requirements for a protein-dense feed • effect on cost structure and milk price risk • N leaching and greenhouse gas emissions. Whichever strategies you employ during spring, pasture surplus management will be critical to your success. Be proactive by identifying surpluses early through regular assessment of your pasture covers and use of a feed wedge. Actively drop paddocks out of the round when an upcoming surplus is identified, and try to consistently achieve your target post-grazing residuals. Also, remember to communicate with your contractor in advance, as their availability may be challenged this season due to COVID-19.

Key points

1. N is likely to be more cost-effective than PKE at generating silage, provided you can achieve a good N response. 2. Assess the potential value of additional silage within your own farm system and carefully consider the full costs, market and environmental footprint. 3.  Accurate surplus management is key, regardless of your strategy.

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Inside Dairy | October/November 2020

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