Rain plays havoc with reproductive heat detection in cows

Applying tail paint.

The wet spring is making it harder for dairy farmers to detect if their cows are ready for mating and could affect reproduction rates.

Detecting cows on heat is critical for a successful herd reproduction programme. Missing or wrongly identifying cows on heat can cost farmers thousands of dollars each year through reduced in-calf rates and later calving patterns.

DairyNZ senior developer Mark Blackwell says the wet conditions, coupled with poor pasture utilisation and their influence on body condition scores, means cows display less evident signs they're cycling and ready to be mated.

"Stress is known to interfere with how cows express they're on heat," he says.

"When they're stressed, their signs are more subtle which makes it more difficult for farmers to know their cows are ready be to inseminated. This means the person responsible for heat detection must be skilled, committed, and attentive to detail," he says.

Some options to help reduce cow stress include once-a-day milking, or increasing feed supplement. Mark recommends farmers seek advice if considering options.

"It pays to get a second opinion as it can be hard to assess your own farm situation objectively."

He recommends farmers be extra vigilant when monitoring heat detection aids and animal behaviour to avoid missing their window of opportunity to be inseminated.

"In difficult conditions consider using a combination of heat detection aids, for example both tail paint and a heat mount detector at the same time. Paddock checks of sexually active groups of cows can also improve heat detection. The definite sign of a cow on heat is that she stands to be mounted."

Other signs include when tail paint is rubbed or removed, a heat mount detector is triggered, if a cow attempts to mount other cows, or if she is restless or bellowing.

"Monitor and manage all aspects of heat detection within your control."

The wet weather has also made it challenging for farmers to manage pasture, with many areas having higher grazing residuals than usual.

About half of the annual feed required on farm is grown and harvested during spring and early summer. How pasture is managed over the next few months will have the biggest impact on the pasture grown, the pasture quality, and late spring and summer milksolids production.

DairyNZ advises farmers to focus on restoring grazing residuals once conditions improve. Some options to get residuals back on track, include grazing paddocks earlier, topping, or making silage/baleage.

* For more information about reproduction, heat detection and pasture management visit the DairyNZ website.