There are several species of pasture commonly grown on dairy farms in Australia, providing farmers with a cost-effective feed source for their cows. Below are details on the most popular species and varieties and information on how to select the best ryegrass variety or cultivar for your farm using the Forage Value Index rating system.
Diploid or tetraploid ryegrass
All ryegrass cultivars are either diploids or tetraploids, which is important to understand when choosing a cultivar for the farm or even specific paddocks of the farm.
Diploids tend to have more tillers per plant, but their leaves are generally smaller and thinner. Diploids are therefore often considered more suitable on farms where overgrazing and pugging may occur during the year or in systems with higher stocking rates. The biggest downside of growing diploids is their slightly lower metabolisable energy compared to tetraploids, and that they can shade out and out-compete clover plants.
Tetraploid ryegrasses are more palatable and therefore cows grazing them tend to have a slightly higher dry matter intake. Tetraploid swards are often more open and have less ground cover than diploids, providing more opportunity for clover to stablish if sown in a mix. Less ground cover, however, can be a challenge in grazing systems where there are higher stocking rates and lead to more problems with weed control due to the greater level of exposed ground area. Remember, tetraploids require a high level of careful management, particularly in wetter conditions, and problems with the persistence of a tetraploid can occur if it is not managed correctly.
Annual and short rotation ryegrasses
Annual ryegrass is usually chosen when post-spring growing conditions are expected to be limiting. The aim of using annual ryegrass is to maximise growth rates while there is still sufficient soil moisture. Similarly, annual ryegrass is often used when a combination of low summer rainfall and soil type do not allow a stand of perennial ryegrass to be maintained year-round. In this way, annual ryegrass is regarded the best crop species to maximise pasture production for less than a year. It can be grown as either a pure stand or in combination with other crops, such as annual clovers or regrowth brassicas.
Short rotation ryegrass, which includes Italian ryegrass, is usually chosen by dairy farmers under similar circumstances to annual ryegrass. Short rotation ryegrass may be more suitable where there is potential for reasonable levels of growth from late spring/early summer rainfall.
New cultivars and a better understanding of its management suggests dairy farmers in southern Australia could reassess the potential of tall fescue in their farming systems. Tall fescue has greater summer growth than perennial ryegrass with at least a similar nutritive value. Grazing of tall fescue needs to be more strictly managed than perennial ryegrass to achieve its potential nutritive value. But there are benefits, including that tall fescue is better adapted to hot and dry conditions than perennial ryegrass due to its deeper root system and higher temperature ceiling. This makes it potentially attractive to farmers located in low-rainfall regions. Tall fescue can also grow in less fertile soils is tolerant to a wider range of pH and waterlogging conditions and can achieve higher persistency than perennial ryegrass.
Kikuyu can provide moderate to good quality forage for dairy cows in both summer and autumn. It is higher in fibre and lower in metabolisable energy than other species such as ryegrass. However, under good management, metabolisable energy levels of 9–10 megajoules per kilogram of dry matter can be achieved. Kikuyu requires high soil fertility to thrive and the best way to achieve this applying precise grazing management.
Perennial legumes such as red clover and lucerne have good drought tolerance than most perennial grasses. The nutritional value of these species is less affected in summer than perennial ryegrass. Lucerne is a good option to provide feed in summer and adapts well to grazing conditions under the right management. Red clover and white clover perform best when combined with perennial grasses or herbs to increase summer feed production and quality. All perennial legumes tend to increase nutritive value and milk production response of grass-based diets. Bloat risks should be considered but they can be managed. Feed allocation is a key factor to reduce the risks. Lucerne, red clover, and white clover all require soils with good fertility to perform and lucerne in particular requires well-drained soils.
Endophytes are fungi or bacteria that live within a plant which can boost pasture persistence where insect pressure occurs. The right endophyte can help pastures withstand insect pests while remaining safe for cattle. Commercial ryegrass and fescue seed is sold with or without an endophyte and different pasture cultivars can contain different kinds of endophyte. Some cultivars are available with more than one type of endophyte. When resowing your pastures, it is important to consider which cultivar and which endophyte, if any, is best for your situation.
Forage Value Index
The Forage Value Index is a tool that helps Australian dairy farmers and their advisors to make informed and profitable decisions when selecting ryegrass cultivars. It provides an accurate, reliable, and independent assessment of the potential economic value of ryegrass cultivars across three different species - perennial, annual and Italian ryegrass - in several dairy-producing regions across Australia. Every year, the Forage Value Index is updated with new trial data to ensure the rankings are as accurate as possible and that any new commercially available cultivars are represented.