Breeding for heat tolerance

15 Jan, 2018 04:00 PM
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Leading Holstein breeder, Trevor Parrish from Kangaroo Valley, NSW, intends to add breading for heat tolerance to his tool box for managing his herd in hot, humid weather.
You wouldn’t pick their ability to handle hot weather by just looking at them....
Leading Holstein breeder, Trevor Parrish from Kangaroo Valley, NSW, intends to add breading for heat tolerance to his tool box for managing his herd in hot, humid weather.

WHEN bull-buying clients started asking Holstein breeder Trevor Parrish about the new Heat Tolerance ABV, he knew he had to make sure he was breeding what his customers wanted.

Mr Parrish runs Illawambra Holsteins in the Kangaroo Valley, NSW, selling about 30 bulls and 100 females a year to other dairy farmers, with these sales making up a sizeable share of the farm business.

The Illawambra herd ranked number one in Australian Holstein herds for profit (Balanced Performance I - BPI), health (Health Weighted Index - HWI) and type (Type Weighted Index - TWI) in DataGene’s August 2017 release of Australian Breeding Values (ABVs).

While leading the breed indices, Mr Parrish is now also considering the Heat Tolerance ABVs in his breeding decisions.

“If bull clients are asking about an ABV then I need to make sure we can provide bulls that meet their requirements and the new heat tolerance ABV is no different,” Mr Parrish said.

Illawambra genetics have sold to Queensland and the north Coast of NSW as well as locally, making heat tolerance an important consideration for some buyers.

“We have bull clients coming to us looking for BPI combined with calving ease, polledness and now heat tolerance, so we need to make sure we are breeding cattle which meet the demands of our buyers now and into the future," he said.

The new Heat Tolerance ABV allows farmers to breed animals with improved tolerance to hot, humid conditions.

In hot, humid weather cows eat less and spend more energy trying to regulate their body temperature.

This can lead to a drop in milk production, lower milk protein and fat tests and reduced in-calf rates.

The Heat Tolerance ABV is a world first, and one of the new generation of breeding values for traits made possible due to advances in genomic technologies and Ginfo, Australia’s national genetic reference herd.

On-farm experience

The Parrish dairy business involves Trevor, his wife Leah, their daughter Toni who has taken over the book work and son-in-law Nathan helps when not doing his electrical job.

The family milks between 160 to 240 cows all year round and have had firsthand experience with the impact of high temperatures on herd production.

“We experience hot summer weather in Kangaroo Valley where we don’t get a breeze, unlike dairy areas near the coast,” Mr Parrish said.

“We also get humidity, which exacerbates the cows’ ability to deal with heat.”

Mr Parrish said while the farm had plenty of shade in the paddocks and at the dairy, production and fertility were affected by hot, humid conditions over summer.

“If we get a run of hot weather we will change our milking times around so we can get the herd back in the paddock and on the pasture before the temperatures get up,” he said.

“Irrespective of what we do on farm, there are cows which don’t eat as much when it gets hot and humid and milk production drops."

Mr Parrish said while making changes on farm were one part of managing heat stress, identifying cows with a superior genetic ability to cope with hot conditions was a significant step in dealing with heat issues in the future.

Breeding program

The Heat Tolerance ABV, is expressed as a percentage with a base of 100.

An animal with a Heat Tolerance ABV of 105 is 5 per cent more tolerant of hot, humid conditions than average.

Its drop in production will be 5pc less than the average.

The Heat Tolerance ABV is favourably correlated with fertility and unfavourably with production, but natural genetic variation means there will be some high production animals with greater heat tolerance.

Its reliability is 38 per cent, which is lower than conventional production traits but in line with the newer generation of genomic-only traits.

This is expected to improve with time as heat tolerance is added into breeding programs.

Mr Parrish has been genomically testing all Illawambra heifers for two to three generations, allowing him to cull on BPI.

“With our females, we focus on the whole herd rather than individual cows and draw a line in the sand for BPI at 150 - if a female is below the required level then they don’t stay,” he said.

“We just need to make sure we identify animals with heat tolerance which don’t sacrifice production and those animals are out there.

“I’m very passionate about breeding bulls and do a lot of research and I’m always looking for bulls that will make our herd easier to manage.

“Now when I get a list of bulls I’m going to be looking for bulls which combine increased production and increased heat tolerance - they are going to be the ones who buck the trend.” Mr Parrish’s experience has shown that cows which have positive Heat Tolerance ABVs are not necessarily light coloured, or have a lot of white.

Some of the females which have the highest Heat Tolerance ABVS in the Illawambra herd have predominantly black coats.

“You wouldn’t pick their ability to handle hot weather by just looking at them which makes an ABV for heat tolerance all the more important if you want to make progress,” he said.

The Heat Tolerance ABV was developed by DairyBio, a joint venture between Agriculture Victoria and Dairy Australia, with funding from the Australian Department of Agriculture and Water Resources.

For more information contact Data- Gene on 03 9032 7191 or abv@datagene.com.au.

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