• There is no advantage to replacing good quality pasture with an alternative feed source or ‘balancing pasture’; therefore, supplements should only be used to provide energy when there is insufficient pasture available.
• There is no evidence that supplementing pasture improves mating performance when there is sufficient pasture supply.
• If feeding supplements results in high grazing residuals, this is wasted feed and the reductions in future pasture growth and quality should be considered.
• When supplements are required in a deficit situation they can help to optimise the area grazed each day, the rotation length, and the pasture residual.

When there is enough pasture, pasture is enough!

The profitability of feeding supplements varies depending on the situation.

• The cost of the supplement.
• Wastage in storage and method of feeding out.
• The associated costs of supplement- these costs associated with feeding supplement can be 50% more than the cost of purchasing the feed, associated costs include capital, fuel/energy, labour, repairs and maintenance and depreciation.
• The degree of pasture substitution, which governs the response rate to supplement. Supplement is more likely to be profitable where post grazing residuals are consistently under 1500kgDM/ha (7-8 clicks on RPM) without the supplement and do not exceed 1,500kgDM/ha with supplement. If feeding supplements results in high grazing residuals, this represents wasted feed. It will reduce the immediate profitability of feeding and have ongoing effects through reductions in future pasture growth and quality which must be considered.

Spring supplement use

Cows should be grazing to a residual of 1500- 1600 kgDM/ha

Cows that are grazing to 1500-1600kgDM/ha are likely to be able to produce more milk if additional feed is added to the system – either as pasture or supplement.

Striking a balance

In spring, striking the balance between the needs of the cow and pasture will optimise the amount of high quality pasture grown and eaten throughout the whole season.  This means attempting to maximise short-term cow intakes ignores the longer term impact on pasture and production.

Maximising intakes to maximise production will result in more pasture being left behind in the paddock. In the graph above the cow will need to be offered an additional 10kg DM to increase intake by 1.5kg DM as she is already close to peak intake.

The difference between the feed offered and eaten goes to increasing the residual, signalling a waste in pasture and compromising quality at future grazing events. Any lift in residuals above the targeted 1500-1600 kgDM/ha means that the strategy is unlikely to be profitable.

Management interventions such as harvesting silage or topping to waste can maintain residuals at the desired level but both incur a cost above the cow grazing pasture. The cost/benefit of the additional feed allowance needs to be carefully evaluated.

Achieving reproduction targets is often cited as a reason for feeding supplement over spring. Research tells us that high quality ryegrass meets the nutritional requirements of the dairy cow, provided there is enough of it. If there is adequate feed (pasture residuals of 1500-1600kg DM/ha with good pasture utilisation) there are no reproductive benefits from feeding additional supplement.

Read more in Feeding cows in spring

Autumn and winter supplement for BCS

Feeding supplement in autumn to milking cows is of limited use for achieving calving body condition score (BCS) targets unless cows were to lose BCS if not supplemented (i.e. insufficient pasture). Cows selected for high milk production preferentially partition nutrients to milk production and not BCS gain. 

 The fastest way to achieve BCS gains is to dry cows off. The timing of dry off depends on your system, BCS gain required and length of the dry period.  If infrastructure exists to achieve high supplement utilisation when feeding dry cows during the winter, this can be a strategy to maximise lactation length while achieving BCS targets. The viability of this strategy depends on supplement cost (incl. associated cost), BCS gain required and time available for BCS gain.

More information

• BCS reference guide for NZ dairy farmers
• Supplement use and making money – the devil is in the detail, SIDE 2014