Expanding the index

The Primary Growth Partnership, Transforming the Dairy Value Chain programme trial will monitor feed intake and growth rates of 100 Holstein-Friesian bulls and 300 heifer half-siblings.
The animals will spend seven weeks next year on feed pens in an adlib feed trial where their feed is measured before and after they eat.
Their live weight would be measured weekly to determine their residual feed intake (RFI), DairyNZ subsidiary, New Zealand Animal Evaluation Limited (NZAEL) manager Dr Jeremy Bryant said.
Residual feed intake is a measure of feed efficiency, and is defined as the difference between an animal’s actual feed intake and its expected feed intake based on its size and growth.
“We are aiming for a negative RFI. The less they need to eat the more efficient they are.”
With the results NZAEL could determine whether there was a strong enough genetic correlation between the bulls and heifers for RFI to be a viable breeding value for use in the industry.
They would require at least a 0.5 genetic correlation, Bryant said.
The bulls selected were second tier from breeding companies’ elite bull contract matings this season. NZAEL and DairyNZ had identified 300 heifer calves born who were half-siblings to the bulls with the same sire using the Dairy Industry Good Animal Database (DIGAD) at DairyNZ and were contacting farmers to lease the heifers for about three months to undergo the trial.
Establishing an RFI breeding value would help improve the accuracy of the Breeding Worth (BW) system to identify the most efficient animals.
“This biological efficiency had always been a bit of a holy grail.”
If the industry could understand what was going on with biological efficiency it would help to enhance the BW model which is focused on finding the most efficient animal, Bryant said.
At this stage RFI is focused on exploring the growth phase of an animal, but past research has also shown animals which grew more efficiently were also more efficient at producing milk.
Eventually they would like to research the efficiency results from lactating cows, but at the moment it wasn’t easy to measure, Bryant said.
“The one missing piece is a lactating cow so we will need to get the genetic correlation between the bull and a lactating dairy cow, but that’s further down the track.
“But we’d expect that fundamentally efficiency is efficiency, there might be a bit of dilution with a lactating cow, but if they’re efficient at growing then it should flow through.”
NZAEL hoped to have a research RFI breeding value for Holstein-Friesians in the second half of 2016 that could be made available to farmers, Bryant said.
From 2017, breeding companies could be routinely RFI testing bulls from all breeds and it might be included in Breeding Worth (BW) or produced as a stand-alone trait.
Previous DairyNZ and LIC research hadn’t found any negative correlation between efficiency and fertility although there had been evidence of a slight negative correlation overseas, Bryant said.
“We would certainly monitor that and look at the relationship of these bulls and their fertility breeding value. That’s why we will take a conservative approach on how high we weight RFI initially in BW.”
Providing this information to farmers would be a valuable tool. If a cow consumes 1kg drymatter less per day for the same level of milksolids production, it could save farmers $85 per year in feed costs for a single cow.
As part of the trial, DairyNZ would also be researching trait predictors by testing the animals’ blood and heat mapping with a thermal image camera in the feed pens.
Overseas research had shown animals losing more heat were less efficient, which made sense, Bryant said.
If there were relationships between blood mid-infrared patterns and thermal images with RFI, farmers could take thermal image photographs of their cows at certain times of the year or test their blood as a predictor of efficiency, he said.
At this stage, producing the genomic-based RFI breeding value was difficult. Accurate genomic breeding values required a lot of feed intake measurements and is very expensive, Bryant said.
This project is funded by dairy farmers through DairyNZ and by the Ministry for Primary Industries as part of the Transforming the Dairy Value Chain Primary Growth Partnership programme.
Fertility breeding value
A calf being born earlier than predicted based on its conception date could be an indicator of a more fertile animal, new research done by DairyNZ and Abacus Bio as part of Transforming the Dairy Value Chain has shown.
The research showed including the gestation length of the animal itself – in terms of how long it was in the gestation period – helped predict the animal’s fertility, Bryant said.
An animal with a shorter gestation had better fertility down the track and passed it on to its offspring.
“If the calf is only in gestation for 270 days rather than the more typical 280 days then that’s an indicator of its fertility. It gives us a big boost in accuracy for the fertility breeding value early in its life.
“That’s good because you get a source of information as soon as the animal is born whereas normally we have to wait until a bull has produced animals and they are starting to calve.”
The second major outcome of the research was improved accuracy through including the calving records of heifers.
“We don’t currently use the heifers’ calving records as two-year-olds. Previously that wasn’t thought to have much value, but we have found it adds value using that information.”
Another enhancement for improving the accuracy of the fertility breeding value was using a cow’s calving date.
Previously the fertility breeding value was structured by either a yes or no answer to whether a cow calved within the first 42 days of the season.
Using the exact calving date as a continuous trait instead of a yes or no answer meant they could get more accuracy in the breeding value, Bryant said.
“These changes will increase the reliability of the fertility breeding value by between 5 and 10% when the bulls are between 0 and 5 years of age.”
If we can get more precise at estimating breeding values we can get greater annual gains in genetic merit because we have greater confidence in it, Bryant said.
Analysing new data
NZAEL has started analysing new data from walk-over weighing from farm dairies to further assess live weight in lactating cows.
The liveweight trait was mainly based on information collected from two-year-olds in sire-proving schemes or pedigree herds, with limited data previously available from older lactating cows.
There was a lot of new data now available in farm dairies with cows weighed at every milking, which would help give more accurate information on this trait.
New technology was being developed to photograph animals and measure their body condition score daily, which was also of real interest to them, Bryant said.
NZAEL would also be collecting new data from farm dairy fixed in-line milk meters which had daily information on milk volume, fat, protein and somatic cell count readings.
This sort of technology could provide a huge amount of data to continue to improve the accuracy of breeding values, he said.
“We try to make continuous improvements all the time to the animal evaluation models and always look to how we can analyse data better.”
Any fundamental changes to breeding values would be held until the animal evaluation transition of data was completed, which at this stage would be in May 2016.