Beef + Lamb New Zealand Genetics’ Low Input Sheep Progeny Trial is identifying the genetics that will future-proof this country’s sheep industry. Part two of this two-part series outlines the management of replacement ewe lambs in the trial and how genes influence feed efficiency and resilience to animal health challenges.
Testing time for ewe lambs
Over autumn and winter, the ewe lambs are shorn and fleece traits recorded. They are run through Portable Accumulation Chambers to measure their methane production (another heritable trait) and in July and August, a representative sample will be sent to Invermay where each animal is tested for residual feed intake- looking at which animal makes the most efficient and effective use of feed resources.
All ewe lambs are retained and while they had reached 40kg by May, they are not mated, although a teaser ram is run with them to identify which lambs are cycling.
Last year, 70% of the ewe lambs cycled.
Cracking two-tooths
In March of this year, the two-tooths weighed 67kg and Robert says they were amongst the best two-tooths he has seen. This is despite none being culled – as would be standard practice.
Robert says genetically, there is a big difference between studs and this reflects the length of the time each stud has been focusing on traits such as worm resistance and dags.
“The genetics work, but it is a slow game, you just can’t put your drench gun away overnight.”
He says the results have shown that no one ram is good at every trait and no one breed is good at every trait.
“The more traits you select for, the slower you will go.”
Dags, for example, are heritable and breeders can move quite quickly to breed those out, but their may be a penalty with slower wool growth.
However, getting rid of dags will potentially stop flystrike and the need to dip lambs.
Robert believes the industry would need five to 10 years notice if it were to stop tailing.
“It will take a while, but it’s certainly do-able.”
Widespread drench resistance forcing the industry’s hand.
While consumers are increasingly demanding lamb produced without chemicals, Robert believes widespread drench resistance – including triple drench resistance- will force the industry into farming without the use of drenches long before regulations will.
“Farmers will be forced into a corner.”
Doing the science
Speaking at the field day were three AgResearch scientists Kathryn McRae, Suzanne Rowe and Tricia Johnson, all involved in some aspect of the Low Input Progeny Trial.
Kathryn talked about using genetic improvement to provide a better product for consumers produced with less impact on the environment.
“We want animals that combine production potential with resilience to external stressors, allowing for production in a wide variety of environments.”
The traits Kathryn focused on in her presentation were internal parasites, pneumonia and Facial Eczema.
FECs
She says individual sheep differ in their ability to develop resistance to parasites and WormFEC is a breeding value- or measure of resistance to parasites.
This is poorly genetically correlated with dagginess.
While Faecal Egg Counts (FEC) are still the best proxy for parasite burdens and a tool to measure an animal’s resistance to parasites, DNA will be used in the future to look at parasite species at the same time as FECs.
Scientists will also be looking at the impact of parasites on behaviour and the interaction between the faecal microbiome and internal parasites.
Pneumonia
Pneumonia is found in 30-40% of all lambs at slaughter. It is costing the industry millions of dollars every year in lost performance.
Kathryn says it is possible to breed animals that are less susceptible to pneumonia and it appears there is possibly a positive genetic correlation between FECs and pneumonia but that has yet to be validated.
Interestingly, animals with lung lesions grow faster from birth to weaning but slower from weaning to slaughter than animals without lesions.
The heritability of a pneumonia lesion score is .07-0.16 which shows that genetic gains can be made.
The next step is to develop an ultrasound as a technology to detect respiratory disease in live animals.
Facial Eczema
This production limiting disease is expected to move further south with climate change. RamGuard is the commercial testing programme for tolerance to Facial Eczema (FE). Tolerance to FE is heritable (0.45) and there appears to be a positive genetic correlation between FE and FEC.
Methane
Suzanne Rowe outlined the work that has gone into identifying and breeding low methane producing sheep. There is an average of a 11% difference in the methane production of high and low methane producing sheep and while the team at AgResearch have measured for everything, they found no correlation between any trait except wool growth. Low methane sheep produce slightly more wool.
Portable Accumulation Chambers (PAC) are used to measure an individual animal’s methane production and is being used in stud flocks around the country.
“There is a lot of variation within flocks which is exciting as it means we can select low methane animals.”
Feed efficiency
A feed intake facility was set-up at Invermay in 2015 to measure actual animal intakes and growth rates. Tricia Johnson says over 1000 animals have been measured and a 22% difference has been found in the extremeanimals in terms of how much they eat for a given live weight and growth rate. The heritability of feed use efficiency is estimated at 0.42 which ihigh.
“Feed is a limiting factor on every single farm operation.
“If we can identify animals and genetics which require less feed for their production outcomes then that would be very valuable.”
For the Low Input Sheep progeny test, between 160 and 200 nine-month lambs are put through this 42-day test. They are scanned at the beginning and end for fat measurements and weighed twice a week. The feed intake of individual animals is measured.
Last year the lambs grew an average 343gms/day in the facility (fed lucerne pellets ad-lib), with a range of 148gm/day to 535gm/day.
Some lambs didn’t put on any fat, others put on a lot.
There was a .5kg of feed difference between the most and least efficient animal.
“There was a big difference between sires in terms of weight gain and fat with some sire lines eating significantly more feed every day and some significantly less.”
Feeding behaviour was also very heritable with highly variable intake rates. Some were eating 600gms/1000 seconds and others eating 200gms in the same time frame.
The number of feeding events also varied between 10 and 80 times /day.
“This was very repeatable for individual animals.”