FARMERS often report that rapid changes to a dairy cow’s diet can lead to dramatic reductions in milk yield, presumably caused by variable feed intake, disrupted rumen function and possible health problems.
A research project at Ellinbank is focusing on reducing these negative effects by redefining the recommendations around diet changeovers in dairy systems.
A recent experiment carried out by PhD student and research scientist Victoria Russo investigated the use of different strategies for introducing a large amount of wheat grain (8kgDM, equivalent to 40 per cent of total DM intake) to late lactation cows previously being fed only lucerne cubes.
The wheat was either introduced rapidly over six days or gradually over 12 days, and either in large increments of 2.7kg or small increments of 1.3kg.
The results were unexpected and showed no matter which strategy was used, no detrimental effects of grain introduction were seen in terms of intake, milk yield or ruminal pH.
Nor were there any signs of acidosis.
Ms Russo speculated that the lucerne cubes helped to buffer the pH of the rumen, thus preventing the drop in ruminal pH typically seen when a highly fermentable starch source was fed out rapidly.
This suggested that the effects of diet changeovers on rumen function were driven not only by the characteristics of the grain being introduced but also by those of the forage.
Collaborators on the project were the University of Melbourne and Teagasc: The Irish Agriculture and Food Development Authority.
Dairy Australia and the Victorian Government have funded the project.
For more information email Victoria Russo at