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Gene Markers Could Boost Milk Production By 25 Percent

Dr Kevin Smith, Senior Plant Breeder, Department of Primary Industries, Hamilton

By Department of Primary Industries - 29th October 2003 - Back to News

Dairy farmers could see milk production lift about 25 percent thanks to scientists working to find markers for genes that control forage quality.

The research supported by the farmers through Dairy Australia has simplified the task of selecting more nutritious perennial ryegrass strains.

A research team led by Kevin Smith of the Department of Primary Industries is evaluating conventionally bred hybrid ryegrass lines for water-soluble carbohydrate (WSC) content and other important attributes.

While improved perennial ryegrass cultivars with increased WSC concentrations are still some years away from commercial release, they have the potential to raise the profitability of dairying throughout temperate Australia by increasing milk production from pasture and also reducing reliance on grain-based supplements.

The genetics improvement of forage quality in ryegrass offers a direct way of delivering increased forage quality to the dairy industry through seed sales of improved cultivars.

Further testing is required but it appears that this source of improved forage quality will be expressed reliably across a range of Australian dairy environments.

Discovery of the markers for important genes has simplified the task of finding plants with genes of interest and will allow faster development of new cultivars.

The researchers use laboratory techniques to detect the markers. Plants were crossed from the high WSC donor cultivar Aurora with a broad range of lines derived from the major perennial ryegrass cultivars used in Australia and New Zealand. The resulting hybrid plants are being evaluated for persistence and performance under Australian conditions.

Elite plants with high WSC concentrations will be combined to form experimental synthetics for further testing.

More than six million hectares of pasture in south-east Australia contain perennial ryegrass as the major sown grass species.

In high-rainfall coastal and tablelands areas, dairy farmers prefer ryegrass to other perennial grass species because of its ease of establishment and high nutritive value.

In Britain perennial ryegrass cultivars with increased WSC concentrations increased milk production by 25 per cent from 12.6 to 15.3 kilograms a day.

Australian researchers estimate that increased WSC content would lift production by a similar amount.

High WSC cultivars from Britain express the high WSC trait when grown in a range of Australian dairy environments including Condah and Kyabram in Victoria, and Gatton in Queensland. However the herbage production and rust resistance of these cultivars is poor compared with adapted cultivars.

The British cultivars have other disadvantages including relatively low root production and poor rust resistance so the researchers are selecting for these traits as well as WSC concentration.

The newly-discovered markers for the high WSC trait will allow more efficient incorporation of high WSC into adapted ryegrass lines without introducing too many unwanted traits from the poorly adapted donor parent.

THE FACTS ON FOOTROT

Footrot is a serious disease that has long been dreaded by sheep owners. It is a disease that causes severe economic loss, suffering due to lameness and disruption to normal farm operations.

Footrot is an infectious and contagious disease caused by the bacteria Dichelobacter nodosus (D. nodosus for short). This organism may also infect goats and, occasionally, cattle.

Virulence varies widely between the various strains of bacteria. Bacteria of low virulence have poor ability to under‑run the hoof horn and, therefore, mostly affect the skin between the toes. This is called benign footrot.

Under ideal conditions virulent footrot will rapidly under‑run and separate the hoof horn from the foot. Most bacteria fall somewhere between the benign and virulent extremes.

When assessing virulence by examining feet it is important to consider the environment of the sheep's foot and the time since infection.

Footrot requires warm, moist conditions for ideal multiplication. The bacteria can only survive away from the foot for a maximum of 7 days, even in ideal conditions. In less favourable dry conditions, the bacteria die rapidly.

Spread of footrot is primarily from foot to foot via pasture or mud. Goats, cattle and possibly vehicles can act as carriers. However moist pastures, laneways and muddy yards are the main areas where footrot is spread.

Footrot will spread most rapidly when conditions are warm and moist, as in spring and some autumns.

Sheep that have been infected with, or exposed to, footrot do not develop any significant natural immunity or resistance. Short term immunity can be achieved using vaccines.

All breeds of sheep and goats can contract footrot, although British breeds are less susceptible. Foot shape and structure affect susceptibility. Goats are usually less severely affected, and may exhibit different symptoms to sheep infected with the same strain of bacteria. Merinos are often the most susceptible and most severely affected.

Low virulence strains are most severe in Merinos but are also seen in British breeds, goats and cattle.

In most cases footrot is a preventable disease. It is virtually always carried into a property and flock by means of a carrier sheep or goat. Prevention is by thorough examination, foot‑bathing and movement control.

Damage control is minimising the effect by isolation and checking all new sheep until removed, or until sheep go through spring with no sign of footrot.

Introducing an infected sheep or mob is bad enough but to allow it to spread the disease to others or all mobs on the farm is a disaster. Treat all new and stray sheep as risks, keep them isolated, handle and visit them last and watch them carefully.

Footrot of sheep and goats is a scheduled disease under disease control legislation. This means that:

• Outbreaks of footrot must be notified to an Inspector of Livestock.
• It is illegal to sell infected sheep or goats, other than for slaughter.
• It is illegal to place footrot-infected sheep in, or adjacent to, any saleyard or in any public place (including a road).

Footrot is a disease that can affect a whole community, not only by spreading disease, but also by creating unnecessary ill‑feeling - and even hostility between neighbours and friends. These affects can be avoided and, in fact, a very constructive attitude created by working together as a community to solve a problem.

Expert advice on diagnosis, treatment and program design to quickly eradicate footrot is available from your veterinarian or DPI Animal Health Officers or Veterinary Officers.

POST FIRE WEED CONTROL

In response to the Bogong Complex fires earlier this year, the State Government has made additional funding available for an increased weed inspection service to landholders in fire affected areas.

Landholders in the fire-affected areas have experienced conditions that may have necessitated the importation of fodder. Given that the fodder has come from many locations throughout Australia, there is particular concern about the introduction of weeds not normally found in the area.

Early detection, identification and treatment of noxious weeds is the best way to minimise the opportunity for them to become established on individual properties throughout East Gippsland

To determine what weeds may have come in with fodder, DPI staff have sent a questionnaire to all landholders in the fire affected area who have already registered with the Department for assistance after the Bogong Complex fires. Landholders are asked to take a few minutes to complete the questionnaire about the type of fodder imported and its origin.

Source: http://gippsland.com/

Published by: news@gippsland.com

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