Stock Unit Calculator

A stock unit (SU) is the standard measure of livestock feed requirements used throughout New Zealand farming. One SU is defined as the feed requirement of a Merino ewe equivalent, consuming approximately 550 kg of dry matter (DM) per year. The stock unit system was developed to allow farmers to compare and aggregate different classes of livestock on a common basis, making it an essential tool for farm planning, stocking rate calculation, and benchmarking. When a farmer knows the total SUs on their property, they can assess whether their pasture can sustainably carry that number of animals and make decisions about supplementary feed, livestock trading, or subdivision. Stock units are used by farm consultants, banks, and rural valuers as a fundamental measure of a farm's carrying capacity. Source: Beef + Lamb New Zealand (beeflambnz.com); DairyNZ (dairynz.co.nz).

New Zealand uses standard stock unit (SU) equivalences to convert different livestock classes to a common measure. Key equivalences are: mature-age (MA) ewe = 1.0 SU (the base unit); hogget = 0.8 SU; MA beef cow and calf = 6.5 SU; yearling beef cattle = 3.0 SU; dairy cow = 5.0 to 6.5 SU depending on breed and production level; deer hind = 1.8 SU; goat = 0.8 SU. These figures reflect the relative feed demand of each class and are used for stocking rate planning and farm comparisons. Note that figures can vary slightly between regional farming systems and updated research. For example, a high-producing Friesian dairy cow may be allocated a higher SU value than a Jersey on a smaller dairy system. Always check with your farm consultant for the most current regional equivalences. Source: Beef + Lamb New Zealand (beeflambnz.com); DairyNZ (dairynz.co.nz).

To calculate total stock units (SU) on your farm, multiply the number of each class of livestock by its SU equivalence and then sum all the results. For example: 500 MA ewes x 1.0 SU = 500 SU; 200 hoggets x 0.8 SU = 160 SU; 30 beef cows with calves x 6.5 SU = 195 SU; total = 855 SU. To calculate your stocking rate, divide total SUs by your effective farm area in hectares. For example, 855 SU on 100 ha gives a stocking rate of 8.55 SU/ha. This figure can then be compared to regional benchmarks or used to assess whether your pasture is being over- or under-utilised. Most NZ farm management software and farm planning tools include SU calculators. Tracking SUs over time helps identify trends in farm productivity and feed demand. Source: Beef + Lamb New Zealand (beeflambnz.com).

Stocking rates in New Zealand vary considerably by farm class, region, and pasture productivity. Typical benchmarks are: sheep and beef hill country 6 to 12 SU/ha; developed sheep and beef flat to easy hill country 8 to 15 SU/ha; dairy platform 3.5 to 4.5 cows/ha, which equates to approximately 18 to 25 SU/ha. Higher stocking rates are achievable with irrigation, high-fertility soils, or intensive management. In drought-prone regions such as Hawke's Bay and Marlborough, stocking rates are generally lower to manage feed risk. Stocking rate is one of the key drivers of profitability in pastoral farming, but carrying tō many stock relative to pasture supply leads to pasture deterioration and poor animal performance. Beef + Lamb NZ and DairyNZ both publish regional benchmarks through their annual farm surveys. Source: Beef + Lamb New Zealand (beeflambnz.com); DairyNZ (dairynz.co.nz).