Feeding and Grazing

Selecting the correct pastures to go on your farm is like putting a puzzle together, each piece has its place. However, if a piece is incorrectly inserted the picture might not look as you had hoped.

Ryegrasses in New Zealand are split into five categories: annual, Italian, short rotation, long rotation and perennial. Annuals are short lived, rapid-to-establish ryegrasses, while perennials are at the other end of the spectrum and live longer but are slower to establish. However, it is important to note that no grass lasts forever.

When selecting pastures for your farm it is important to get the large pieces (typically perennial or long rotation ryegrasses) of the puzzle in the correct places. Perennial or long rotation grasses are categorised by their heading date. The heading date is the time in spring when seed heads first become visible in the pasture. Why is this important? Ryegrass has approximately a six week burst of growth prior to the seed head emerging. Once seed heads emerge we see a decline in pasture quality due to more stem, an increase in dead material and less leaf. Having a minimum of two different heading date areas on your farm enables you to more strategically manage pasture growth and quality i.e. no more than 50% of your farm should be in one heading date.

Annual, Italian and short rotation ryegrasses can be used to undersow into existing pastures to thicken them up or extend their longevity until they are regrassed or as a pure sward pasture “crop”. In areas with high insect pressure, such as black beetle, the use of nil endophyte grasses (i.e. annuals/ Italians) undersown into existing swards should be restricted to paddocks that are nearing pasture renewal. Alternatively, they can be used as a pure sward in paddocks that are to be taken out the following spring for crop.

Questions to ask when establishing what your farms perennial or long rotation ryegrass needs are:

• What are the existing pasture cultivars on my farm?
• What are their heading dates?
• What area of farm is planted in them?
• Paddock use (e.g. lambing, sick cow paddock)?
 

Piece 1: Mid-season heading ryegrass.

• Paddocks close to dairy shed (i.e. a sick cow paddock), paddocks needed in the first 2-3 weeks after calving, and night paddocks
• Lambing/calving area

Piece 2: Late heading ryegrass.

• Feed for early in the season to lift cows towards peak production
• Feed to lift milk yield of lactating ewes and beef cows for improved lamb and calf live weight gain

Piece 3: Very late heading ryegrass.

• Feed for dairy cow mating, to hold cows at peak production and to help slow the rate of dropoff of peak production
• Feed to hold ewe milk production post-peak production period, boost lamb live weight gains allowing more lambs to be drafted to the works off the ewe
 

The Grass Selection Guide is a useful guide for choosing what grasses would suit your situation through selecting soil type, pasture life and grazing management.

For more information on grazing management please see product pages.

Please note that: This diagram is intended as a guide only. For specific recommendations on the grasses best suited for your farming system, contact your local seed retailer, one of your local PGFG Wrightson Seeds Representatives or call 0800 805 505.

Valuing forages on a megajoule of metabolisable energy (MJME) basis is a handy and straightforward concept. For all stock classes, we can balance an animal’s requirements:

• Demand for energy (maintenance, live weight gain, pregnancy and lactation) with
• Supply of energy (MJME/kilogram of dry matter (DM) multiplied by kgDM eaten per day)

By defining animal production targets (e.g. kilograms of live weight gain or milksolids), the MJME rating of a feed and the kgDM available, we can develop a feeding plan that allows animal’s to meet these performance targets. However, MJME is simply a calculated measure of forage quality; it doesn’t take into account other factors that drive the production performance of forage-fed sheep, cattle and deer. Other nutritional factors of forage such as crude protein (CP), neutral detergent fibre (NDF), water soluble carbohydrates (WSC), fat and minerals can affect animal productivity too. Looking at MJME in isolation will not necessarily predict animal performance.

Crude Protein (CP)
High concentrations of rapidly rumen degradable crude protein (CP) often accompany high MJME feed test results. Leafy, lush high MJME spring or autumn pasture may contain CP levels in excess of 30% CP. Dairy cows at peak lactation require no more than 20% CP. Lambs growing at 300 grams of live weight per day require no more than 15% CP.

If CP levels exceed the requirements of stock, feed conversion efficiency may fall. Animals can lose surplus protein as urinary urea which is a waste of the animals energy and can potentially reduce the efficiency of your feed.

Neutral Detergent Fibre (NDF)
Inadequate levels of physically effective NDF (peNDF) in high MJME forages may fail to support appropriate rumen function. For a lactating dairy cow, the first autumn grazing of a lush high quality Italian ryegrass testing at
13.0 MJME ‘on paper’ appears to be a perfect complete feed. However, a low concentration of NDF (e.g. 28 to 32%
NDF/kgDM) increases the risk of ruminal acidosis because forage-fed dairy cows require 35% NDF for optimum ruminal function.
Minerals
The risk of animal health issues for stock grazing forage can’t be evaluated on the basis of MJME alone. High MJME lush, leafy pasture often contains high concentrations of potassium and CP, and low levels of magnesium and calcium which increases the risk of metabolic challenges (hypomagnesaemia and hypocalcaemia) for pregnant and lactating cattle. This can occur particularly when the passage of high MJME forage through the rumen is rapid.
Measuring your pasture quality based on only MJME means you could be missing out on identifying potential mineral deficiencies.
Other Factors
In addition to the nutritional factors, the type of forage and the environment can also affect the intake of high
MJME feed:
• The presence of standard endophyte alkaloids, rust, effluent applications to pasture and high concentrations of minerals or compounds including nitrates and sulphur may limit the intake of high MJME forages
• Tetraploid ryegrasses are often consumed more readily than diploid ryegrasses, even when the MJME value for each ryegrass is similar
• Lower than ideal pre-grazing pasture mass (kgDM/ha) can reduce MJME intake. For cattle particularly, reduced bite sizes on short pasture will reduce intake of otherwise high MJME pasture, particularly if grazing time is limited. Wet muddy conditions further reduce utilisation of high MJME forage

The evaluation of feeds based on MJME is better than kgDM alone; however, it doesn’t take into account other aspects of forage nutrition. When working to improve the nutrition of forage-fed stock, we need to understand the importance of all nutrients, not just MJME.

The PGG Wrightson Seeds team consider all aspects of forage quality during the breeding and development of pasture species, giving you forages that will meet the needs of your sheep, cattle and deer.
 

Share this page