July 2010 edition
Improving feed conversion efficiency through genetic markers
Leah DeVries, Dairy Extension Officer, DPI Tatura
DPI’s Future Farming Systems Research, with support from the Gardiner Foundation, has been working on a research project to improve the feed conversion efficiency of dairy cows. The Feed Conversion Efficiency Project aims to develop a set of genetic and biological tests that can be used to identify highly feed efficient cows.
The project involves screening approximately 1,000 calves to determine their feed efficiencies so this could be related to markers in their DNA. The project began in March 2009 at the feeding facility at DPI Rutherglen. Holstein-Friesian calves aged between six and eight months were tested in three batches over a period of 18 months. The calves were provided by farmers across Victoria and were penned in groups of 18 for around 90 days.
The calves had unlimited access to lucerne forage allowing the animals to self-regulate their own feed intake according to their biological needs. The daily feed intake of individual calves was recorded by an electronic feed recording system. The calves were also weighed twice a week to record their live weight gain.
Feed Conversion Efficiency (FCE) is usually thought of as the production output per unit of feed eaten, i.e. milk yield per kg feed intake. However, this research project is looking at a different aspect of feed efficiency which is metabolic efficiency. Metabolic Efficiency relates to how the cow uses energy to maintain itself and also produce milk. Some cows are able to use less energy than others to maintain their bodies whilst producing the same amount of milk.
To determine the metabolic efficiency of the calves a measure called Residual Feed Intake (RFI) was calculated. RFI is the difference between what a calf is expected to eat based on its body size and production level and how much the calf actually does eat.
RFI = expected intake – actual intake
A cow that eats less than expected is metabolically more efficient as she can consume a lesser amount of feed to maintain herself.
DNA samples were taken from the calves to perform an analysis for genetic markers. The DNA markers and the feed efficiency information will be used to develop a set of genetic and biological tests to predict feed efficiency. Ultimately farmers will be able to use the test to select animals based on their feed conversion efficiency, enabling them to make better breeding decisions. The hope is that with the use of genetic and biological markers, Australian dairy farmers will be able to improve the feed conversion efficiency and profitability of their herd.
The 30 most efficient and 30 least efficient calves from the first and third batches were purchased to create a herd of 120 cows to use for further research into feed efficiency. This research will test whether the efficient calves end up as efficient milking cows. It will also investigate how other management factors affect the efficiency rankings of the cows i.e. will the rankings change when cows have a restricted feed intake compared to an unrestricted intake?
Look out for the project results involving the calves at the feeding facility in a future edition of the Mountain Milkline.
