Trials seek optimum high merit system
Trials seek optimum high merit system
HIGH merit dairy cows managed on four different systems have produced similar levels of performance according to first years results from trials in Northern Ireland.
Conrad Ferris, based at the Agricultural Research Institute at Hillsborough, told dairy farmers that the results had been obtained despite different feed, land and management inputs.
"What is the optimum system within the four we have looked at? That is impossible to answer. It depends on the land, economics and management and highlights the need for individual milk producers to fully evaluate their businesss resources," said Mr Ferris.
The Hillsborough trial looked at four grassland-based systems of milk production for winter calving cows. Each system was designed to achieve increased nutrient intakes with high merit animals.
"Compared to medium merit cows, high merit cattle sustain higher milk yields by using more of their body reserves for milk production and by directing more of their feed nutrients into milk rather than body reserves. Consequently, achieving higher nutrient intakes is a key management issue for high merit cows," said Mr Ferris.
Early trial work on high merit cows at Hillsborough proved they were capable of higher levels of production, but where was that milk coming from?
"As you would expect, high merit cows eat more; our studies have shown it amounts to 1.1kg of dry matter a day compared with medium merit animals. But the yield advantage from high merit cows was only 4.3 litres of milk a day. Clearly the two figures do not add up. "
Hillsborough researchers have investigated how efficiently cows produce milk in the udder. Results showed that medium and high merit animals digest their feed in exactly the same way; in the udders of these cows there was no difference in the efficiency of milk synthesis. "We did assess body tissue reserves and saw, as expected, that high merit cows lost 0.1 unit of condition score during a lactation compared with medium merit cows, which gained 0.4 unit of condition score.
"In early lactation the high merit cow burns off much more body tissue reserves for milk production; the medium merit cow, in later lactation, starts to look after herself again and pushes nutrients into back-fat."
So what are the implications for high merit cows? Mr Ferris said higher nutrient intakes must be achieved otherwise cows moved into second and third lactations carrying too little condition and performance and longevity suffered.
Hillsborough designed four systems to evaluate the performance of high merit cows. "These systems gave us a range of options. They enabled us to play around with the digestibility of silage; get more nutrients into these animals in summer by extended grazing and by feeding concentrates at grass and varying herbage allowances."
Results at the end of the first year of the four systems show that while MOFF a cow and a litre were relatively similar on each, margin a ha increased when concentrate feeding increased.
For cows receiving a high feed value silage plus 6kg of 26% protein concentrate in winter and an extended grazing regime from late-February with 0.5kg meal fed at grass, a MOFF/ha of £2160 was achieved.
At the other end of the scale cows were fed a medium feed value silage plus 12.5kg of 18% concentrate and turned out on Apr 1, stocked tightly and fed to yield. MOFF/ha was £2840. *
High genetic merit cows must achieve higher nutrient intakes, says Conrad ferris.