Supported by Dairy Australia’s northern regional development program Subtropical Dairy, the trial will compare four perennial grasses – kikuyu, setaria, paspalum and Rhodes – and the forage crops millet and sorghums.  

These are all C4 forages, which are more adapted to warm or hot seasonal conditions under moist or dry environments; all have only moderate nutrient quality, generally well below that of temperate species like ryegrass and prairie grass.

However, according to project leader Bill Fulkerson, a recognized authority on tropical pastures and now a field officer with the Norco milk processing cooperative, well managed kikuyu, and probably setaria, are good for 14 litres/day for a Holstein-Friesian cow.

That level of production should rise to 18 litres per cow with four to five kilograms of grain, plus minerals which are deficient in these grasses, and that would be “cheap milk”. 

Dr Fulkerson said the trials would see the four grasses managed to optimize quality, based on regional experience with kikuyu, and with best practice management of the millet and sorghums.

“A good deal of research has been undertaken on management requirements for kikuyu, with the main objective being to optimize nutrient quality,” he said. 

 “But the persistence of kikuyu is often poor because of the fungal disease kikuyu yellows and this, as well as the subsequent difficulty in re-establishing kikuyu, has created interest in growing one of the three other summer grasses or in millet or sorghum to provide summer feed.  

“NSW north coast dairy farmers have widely differing views on the benefits of the six forages, based mainly on very anecdotal evidence.

“However some recent analysis of setaria indicates its nutrient quality can be as good as kikuyu if managed in a similar way. 

“That includes an appropriate grazing interval, mulching to encourage higher quality new leaf and adequate fertilizing.”

Dr Fulkerson said a major issue for the trial was the problem in growing the forages under conditions that would allow for a valid comparison but still within a dairy context. 

The slow and unreliable establishment of the four grasses – perhaps up to three years to grow uniform swards – meant that it wasn’t possible to start the study at this point.  

“We needed to compare performance over a number of on-farm sites where two or more grass species were already established, allowing inter-relation of data.

“Paddocks chosen on a particular farm would need to have had similar paddock histories, with similar soil nutrient levels, confirmed in the spring and remedied by application of appropriate fertilizers.”

For the grasses appropriate management would involve grazing at 4-4.5 leaves per tiller – about every two weeks in mid-summer – and mulched back after grazing several times during summer to promote leaf growth. 

Every second grazing would be followed by application of about 50kg/ha of nitrogen fertilizer. 

Dr Fulkerson discussed “management of summer grasses for optimum milk production” at a Subtropical Dairy field day in Casino.

He said kikuyu was the dominant summer pasture on coastal dairy farms and, while it was capable of high summer growth, milk production could be limited by the grass’s relatively low quality. 

Cows grazing kikuyu could produce up to 14 litres of milk a day – still considerably less than the 18 to 20 litres expected from ryegrass – as long as the kikuyu was well managed and the cows were supplemented with high, energy-dense, cereal based feed as well as minerals to address deficiencies in the grass.

Cereal based concentrates could be fed to achieve higher milk production and the response to the first three to four kilograms per cow per day was excellent.  

On the pasture side, grazing intervals had to be managed to maximize the amount of kikuyu leaf available to cows and reduce the development of stems. 

Grazing at the 4.5 leaf stage provided the highest proportion of leaf and the highest quality grass for cow consumption.