Test highlights power of genetics

Widespread drench resistance, labour shortages and changing market demands are all challenging today’s sheep farmers as they strive to maximise production while reducing inputs.

These factors were the drivers behind Beef + Lamb New Zealand Genetics three-year low input progeny test (LIPT) run on South Canterbury’s 4000ha Orari Gorge Station.

With its 1200mm annual rainfall, the farm is considered summer-safe but this comes at the cost of significant internal parasite challenges, making the property an ideal testing ground for low-input genetics.

Owned and farmed by Robert Peacock and his family, Orari Gorge runs from 200 metres above sea level to 1000m with 75% of the country described as tussock hill. Only 10% is flat and the balance is rolling. It carries 9000 ewes, 700 Hereford breeding cows and 2000 breeding hinds. This is a ratio of 50% sheep, 25% cattle and 25% deer.

To carry out the test, every year 17 rams from a range of breeds were submitted from breeders throughout the country. All participating breeders have been selecting for low-input traits.

Robert’s commercial ewes were artificially inseminated and pregnancy scanned and the progeny DNA tested at tailing. Tail length and the length of the bare skin under the tail were also measured. These were the first of many measurements taken of the progeny, others included weaning weights and growth rates, faecal egg counts (FEC), dag scores, eye muscle area, carcase data, wool weights, hogget oestrous, methane emissions and residual feed intake.

As the trial enters its final stages, a field day was held at Orari Gorge to summarise some of the findings.

wasn’t too much of an issue either year.

Robert does question whether flystrike is a trait that could be selected for as has been done in Australia in Merinos.

TAILS

• While tail length and bareness are highly heritable, there is little variation within breeds. This means progress will be slow without outcrossing.

Over the course of the LIPT, tail lengths of the ram lambs were measured and scores allocated from 1-3. One being a short tail (less than 15cm) and three being a longest (more than 25cm). The length of bare skin under the tail was also measured and bareness traits (belly and breech) were also scored.

Tail length, tail skin bare breech and bare belly are all highly heritable traits, however, for some breeds such as the Romney, there is little within breed variation for traits such as bareness and tail length. This means it will take a long time to make any progress without outcrossing.

METHANE

• Rank rams based on performance and breeding objectives, then select the ones that are emitting less methane.
• Very few other traits are related to methane.

Over the course of three years, a total of 848 methane emission measurements were taken. Half of the measurements were taken from sheep taken off pasture, the other half were taken from lambs on a grain pellet diet (as part of the residual feed intake trial).

This number of measurements has generated some valuable data for the industry and highlighted a huge variation in methane emissions within flocks and breeds.

AgResearch’s Dr Suzanne Rowe led much of this work and explains that an animal with lower methane emissions will have a negative breeding value, so ratings go from low to high. But for the commercial breeder, her recommendation is to rank rams based on performance and breeding objectives, then select the ones emitting less methane.

The number of studs recording for methane has increased from three to 30 in the past three years and will likely increase significantly with farm emission taxes looming.

Very few traits are related to methane, but research has shown lower methane emitting sheep eat slightly less feed and produce more wool than higher emitting animals.

AgResearch is working on adding methane emissions into the Maternal Worth Index by putting a value on carbon at $100/tonne.

An increasing number of stud breeders are getting rams tested through AgResearch’s Portable Accumulation Chambers (PAC) and Dr Rowe is encouraging breeders not just to measure their top sires.

“They need to measure all their sires to get a feel for what’s in their flock.”

An emerging technology in methane emission measurement is rumen samples. Samples were taken from animals in the LIPT and the results correlated with PAC measurements. Early indications suggest the results from both are closely correlated, which would make emissions testing a lot easier, especially for larger species such as cattle and deer.

RESIDUAL FEED INTAKE

• The trial highlighted a massive difference in feed intake amongst individual animals to achieve the same outcomes
• There was also a massive variation in feeding behaviour
• Feeding behaviour is highly heritable.

Every year of the LIPT, a sample of nine-month-old ewe lambs was sent to Invermay’s Feed Intake facility to measure their residual feed intake and feed efficiency. This was calculated by measuring the actual intake minus predicted intake (based on their requirements for maintenance and liveweight gain.)

After a period of adjustment to the pelletised grain feed, the feed intake of each animal was measured for 42 days. In the 2021 cohort, the average growth rate of these lambs was 272g/day. The minimum growth rate was 72g/day and the maximum was 400g/day.

This trial highlighted a massive difference in feed intake to achieve the same outcomes. There was also a big variation in feeding behaviour, with some animals eating 100g in 500 seconds and others eating 300g in the same timeframe.

The 2021 results were consistent with results from previous cohorts.

Dr Tricia Johnson is leading this work and she says Residual Feed Intake is highly heritable with an estimated heritability of 0.42.

“Feeding behaviour is really heritable and we do know there is a small relationship with methane.”

CHRONIC NON-PROGRESSIVE PNEUMONIA

• Between 30-40% of lambs between the age of three and 10 months will have some form of pneumonia.
• Multiple agents are involved with pneumonia
• It is a heritable trait.

Processing data has shown that 30-40% of lambs between the age of three and 10 months will have some form of pneumonia in their lungs and this increases as the processing season progresses.

AgResearch scientist Kathryn McRae, says in 2008, pneumonia was estimated to cost the industry $53 million annually as a result of reduced growth rates and downgraded carcases.

Multiple infection agents are associated with pneumonia; it can be caused by a virus, bacteria or mycoplasma.

There is a variation in an animal’s susceptibility to pneumonia and it is heritable with a heritability of between 7% and 16%.

There is a positive genetic correlation between pneumonia and Faecal Egg Counts (FEC), so breeding for FEC may result in reduced susceptibility to pneumonia.

Animals that are able to cope with worm burdens may be better able to cope with pneumonia. Lambs with pneumonia lesions tended to be those that grew faster from birth to weaning then slower from weaning to slaughter than animals without lesions.

The next step is to carry out ultrasound work on live animals as all the information so far comes from processing data.

PARASITES

• Genetics is not a short-term fix for internal parasites but it is a long-term solution.

Drench resistance is getting worse and it’s not just a North Island issue. Central Otago and North Canterbury vet practices are reporting 30-35% of triple drench resistance in their data sets.

Internal parasite resistance is a moderately heritable trait (30%) but sheep need to remain productive so making selections based on maternal worth and FEC will allow commercial breeders to make progress.

The LIPT identified fast growing, low-FEC undrenched lambs even in the face of the significant challenges they experienced on Orari Gorge.

Lambs born in the LIPT were drenched at weaning and left undrenched until May. FECs were carried out in February and May. Each year a small group of 25-30 lambs in the LIPT were kept as a control mob and these were drenched every six weeks.

Some of the undrenched lambs were not far behind the drenched lambs in terms of growth rates.

Robert says he found a clover crop to be valuable tool in driving growth rates and off-setting the production limiting impacts of internal parasites. This is because internal parasites cause protein (critical for growth) to be lost from the lambs’ gut and protein-rich clover (or any legume) off-sets this loss.

Ultimately, breeding is the best long-term solution to managing internal parasites.

RECORDING AND CONNECTIVITY

• Since the start of LIPT, the number of breeders recording low input traits has increased significantly.

As a ram breeder, who has been selecting for low input traits, Robert Peacock says he put his hand up to host the LIPT because he was finding it increasingly difficult to find outside sires from studs recording those traits.

“I was restricted by where I could buy low input rams with high production and I wanted to find rams that could prove themselves in my environment.”

He was also aware of the importance of linkages to help drive the sheep sector forward.

Linkages are critical as they allow comparisons between the breeding values of different flocks. While recording for low input traits was important, connectivity was vital.

“We needed a progeny test that put progeny under a challenge with health traits and to get linkages.”

Stud breeders can’t keep improving their genetics if they have to close their flocks.

“We need each other to drive the industry…”