The feed conversion efficiency trials are part of a joint Australian and New Zealand research initiative.
Feed conversion efficiency is measured by residual feed intake (RFI), a variation of an individual animal’s requirements, relative to other animals of similar liveweight and productivity.
For example, given a situation where two cows have the same liveweight, condition score, and level of milk production, but one of the cows eats 1kg drymatter less feed to do so, that cow is considered to be more efficient than its companion. It is eating less but has the same level of productivity.
Speaking at the Westpac Taranaki Agricultural Research Station (WTARS) open day in November, DairyNZ senior scientist Kevin Macdonald updated progress on the RFI trials that make use of the specialist feed intake measuring facilities at WTARS, now in their third season.
One part of the research involves 126 cows identified through a LIC gene marker identified from earlier research in the programme as being either highly efficient or not very efficient for RFI, split over four farmlets.
The four farmlets differ in stocking rate, ranging from 2.2 cows/ha to 3.6 cows/ha. Within each of the farmlets, the herd has an even split between more and less efficient cows so that comparisons can be made at each stocking rate.
Macdonald said the researchers wanted to know whether at the higher stocking rate – with the animals under greater feeding pressure – the more efficient animals would turn more energy into milk at the expense of condition, and whether the less efficient animals would divert more energy towards condition at the expense of milk production?
“So far we have not been able to pick up any differences,” he said.
He said research based around beef cattle in feedlots suggested the difference was the greatest at higher feeding levels, in this case represented by the lower stocking rate.
The research is also tracking liveweight, body condition and reproductive ability. Researchers have not yet been able to measure and identify any differences in those traits between the more efficient and least efficient animals.
Macdonald said the equivalent trials undertaken in Australia seemed to have identified a difference in reproductive ability.
“The animals used in the study [in Australia] are basically American Friesian Holsteins, much bigger than ours, and they have a much lower reproductive ability,” he said.
“It may be inherent in their animals anyway but we have not picked it up here.”
This season cows are being equipped with pedometers at WTARS to try to confirm data that suggests the more efficient cows walk less and are less active.
