GMP5: Nutrient and Cost Analysis

GMP5: Nutrient and Cost Analysis

Using a feed pad to stand off stock with Mac and Lynda Pacey

Ag-first assessed the Pacey’s use of their feed pad for standing off stock. The analysis below summarises the nutrient savings, impacts on profit and the wider farm system, risks and additional on-farm skills required to implement this nutrient practice.  
Nutrient losses

FARMAX was used to model a ‘status quo’ system with and without the feed pad. Information used was based on previous years’ actual data provided in historical FARMAX files. Key information from FARMAX was used to model the two scenarios in OVERSEER 6.2.3. A base OVERSEER file was provided by the fertiliser rep and updated after clarification with Mark Pacey.

The ‘feed pad’ scenario was based on peak milking 320 cows, with replacements reared off farm from October and 100 cows wintered off farm for roughly 10 weeks. Imported supplement included 160 t Palm Kernel, 108 t PKE/biscuit mix, 15 t DM hay and 130 t DM pasture silage from the runoff. Another 40 t DM pasture silage is harvested from the milking platform, and all feed including for dries is fed on the pad. Milk production was modelled at 138,557 kg MS.

Research suggests that the impact of pugging damage is worth 3% of total milk production, which equates to 600 kg DM/ha of reduced pasture growth. The pugging damage on Rotomahana mud may be greater than this considering how many farmers in the area stand cows off through winter. It is difficult to put a number on this due to limited research of pugging damage on pasture production alone, therefore the difference in production and profit is potentially greater than presented here.

The ‘without feed pad’ scenario was based on reduced growth mainly through June-August and 10% of the farm regrassed in autumn. Peak milking 300 cows, slightly less replacements and the same number of cows wintered off. Imported supplement included 150 t Palm Kernel, 96 t PKE/biscuit mix and 13 t DM hay, with Palm Kernel fed in trailers. The same amount of pasture silage was harvested and fed from the runoff and milking platform. Milk production was modelled at 128,501 kg MS.

The feed pad was entered as a wintering pad in OVERSEER to account for standing the cows off every night during May to August. Effluent from the feed pad is scraped into a weeping wall, with solids spread on the non-effluent block and liquids treated the same as farm dairy effluent. Susceptibility to pugging was entered as ‘rare’ with the feed pad and ‘winter’ without the feed pad.

In total, whole farm system nutrient losses increased by 783 kg N and 114 kg P by removing the feed pad. Based on the farm’s effective pastoral area, this was an increase of 7.5 kg N/ha/year.

The increase in N losses are likely to have occurred from reduced output as milk product, and more frequent deposits of urinary nitrogen directly onto pasture. The benefit of feed pads is that excreted nutrients are captured into the effluent system and spread over a greater area at a nutrient lower loading rate. Research has shown autumn deposited nitrogen to have the greatest impact on nitrate leaching, as soil nitrogen levels build up due to low pasture growth rates and is flushed through the soil with the autumn and winter rains.

Economic modelling

FARMAX was used to model each scenario, the level of inputs required and the outputs in terms of milk production and profit.
The total cost to install the feed pad and rubber matting was $130,000 spread from 2000 to 2013. The total area covered by the rubber matting is around 850m2. When accounted for in present day value, this is around $170,000. To account for the opportunity cost of investing in a feed pad, at 6% cost of capital this equates to $10,200 per annum (‘Interest’ in the budget below). The total cost for scrapping the feed pad is estimated at $900 per annum plus an additional $3500 per annum for emptying the weeping wall (‘Other costs’ in the budget below).

The FARMAX analysis showed that at an average milk price of $6/kg MS the ‘feed pad’ scenario was $43,927 more profitable than ‘without feed pad’ when the additional costs of capital and effluent are accounted for. As shown below, farm working expenses were similar between scenarios with the ‘feed pad’ scenario purchasing slightly more feed, however the ‘without feed pad’ scenario spending more on regrassing. Although expenses were higher with the feed pad, milk production was 10,000 kg MS higher resulting in more profit. Milk production per cow was maintained at 430 kg MS/cow for both scenarios but the use of the feed pad allowed a higher stocking to be operated, hence greater milk production.

Utilising a feed pad represents a 20% reduction in nitrate leaching.

The key risks

The key risk for farmers looking to invest in a feed pad for environmental purposes need to consider the capital cost and the impact on the farm system. Feed pads can become very expensive especially if the effluent system requires an upgrade. The return on investment needs to be considered and weighed up against other strategies to reduce nutrient losses. There is also the impact on the system – the labour required to feed out on the pad, additional machinery, and the impact on level of feeding. Some farmers find that over time they unconsciously intensify the feed system which will impact on the total property nutrient losses. Getting clear about what problem you are trying to solve and making sure the changes fit within your goals is important

If using a feed pad for standing stock off for extended periods, the use of rubber matting should be considered. Research has shown that cows require a minimum of 4 hours on pasture after standing on concrete, however cows will not graze during this 4 hours, instead they will lie down. Extensive research and consultation with independently qualified people will help with making the right decision.

The key risk of operating without a feed pad is the impact of pasture damage and growth rates and costs associated with regrassing. It requires that farmers are skilled in pasture management, and understand strategies to cope. Pasture covers need to be higher going into winter/spring to prevent expensive supplementary feed bills. The modelled farm had average pasture cover of 2400 kg DM/ha as at 1st June to prevent covers dropping too far below 1900 kg DM/ha in August/September.

Additional skills required
Using a feed pad to stand cows off over winter requires that farmers are more skilled at achieving target residuals as the grazing pressure is reduced. If this is not mastered then pastures will become clumpy and quality will decline. If feed inputs are increased to increase the return on investment then better pasture management skills are required to ensure cows are not substituting supplement for pasture. An understanding of feed nutrient balancing will be required at high levels of supplementation.

Implications for the wider farm system
We would expect cows to be better fed through the winter period resulting in greater body condition scores at calving. Research comparing using a stand-off pad resulted in an increase in empty rates of 6% when no stand-off pad was used. This is likely the result of body condition, stress and feed utilisation during wet periods.