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.
Trevor runs Illawambra Holsteins in the Kangaroo Valley, NSW, selling about 30 bulls and 100 females a year to other dairy farmers.
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).
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.”
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 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 and 240 cows year round and have had first-hand experience with the impact of high temperatures on herd production.
Mr Parrish said that 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.
“We experience hot summer weather in Kangaroo Valley where we don’t get a breeze, unlike dairy areas near the coast,” he said.
“We also get humidity, which decreases the cows’ ability to deal with heat.
“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.
“Irrespective of what we do on farm, there are cows that don’t eat as much when it gets hot and humid and milk production drops.”
He said making changes on farm were one part of managing heat stress, but identifying cows with a superior genetic ability to cope with hot conditions was a significant step in dealing with heat issues in the future.
“We just need to make sure we identify animals with heat tolerance that don’t sacrifice production. Those animals are out there.
“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 that have positive Heat Tolerance ABVs are not necessarily light coloured or have a lot of white.
Some of the females with 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.