Getting heat detection right

 The recent changes to rules on inductions that have the practice banned from spring 2015 means getting cows in calf sooner is crucial. 

Nationally the dairy industry has a target of 78% six week in calf rate, which at present is averaging 65%. Initiatives like LIC’s 6 Week Challenge have raised the profile about the importance of getting cows in calf earlier. This will deliver more days in milk and more valuable high genetic heifer calves to build the herd’s future upon. 

Work by DairyNZ scientist Dr Chris Burke indicates a missed heat represents a loss of $150 per cow. But a combination of careful observation skills and well suited oestrus detection aids will help ensure that loss is minimised.

Heat or oestrus in dairy cows can be as varied as the cows themselves, differing in outward behaviour ranging from overly aggressive or restless, to being withdrawn.

Influences on cycle time

Sexually mature cows will cycle every 21 days, but the time on heat can also vary significantly, from 13-15 hours to only 2-3 hours, and a maximum of 30 hours. 

This can be influenced by the age of the cow: a young heifer will take longer than an older mature milking cow. Good cow condition will result in her cycling earlier after her last pregnancy, later if she is lighter. 

What to watch for

Cow behaviour when on heat brings some distinct signs that indicate the stage of heat the cow is at. When observing behaviour in the paddock, restlessness, sniffing other cows’ tail areas and mounting are all signs she is either coming into heat or is on heat. Observations in the dairy such as swollen vulva, withholding milk and rubbed tail hair are also indications.

A sure sign that a cow is ready for AI is when she stands ready to be mounted by another cow. The mounting cow rubs off the standing cow’s tail paint, making the fact that she is on heat obvious to the observer when she next comes in for milking. If observed in the morning she should be drafted out and inseminated. If observed in the evening, making a note or logging her number into the drafting system will ensure she will be drafted out in the morning. If she does not stand to be mounted it is still too early.

Detecting heat – some options

The most widely used and most cost-effective method of heat detection chosen by NZ farmers is tail painting. 

Ensuring the area is clean, apply paint along the spine from tail head in a 15cm by 5cm strip.

Four colour codes are recommended:

• Red – 3 weeks before calving on all cows will help identify those cows not cycling and requiring attention.
• Green – immediately before starting AI programme to identify cows as they cycle.
• Blue – post insemination, no rubbing 3-4 weeks later indicates she has held.
• Yellow – when pregnancy is confirmed.
• Regular touch-ups are recommended for tail paint.

There are different types of tail paint applications available – aerosols, brush on applicators, tins, buckets and a backpack tail painter to help assist with tail painting large herds.

High-tech options also exist. Heat detection collars are one option that detect when a cow’s activity is elevated while on heat. 

Such technology is common in the northern hemisphere and interest is growing in New Zealand. Especially on intensively farmed properties the high-tech options free staff for other jobs, or sometimes allow a staff member to be replaced.

Whatever method of heat detection is chosen, a set procedure, good observational skills and a proven method will all ensure a tighter calving pattern and more milk in the vat next season.

This article first appeared in Getting the Basics Right 2015 edition.

• Tracy Quin is brand manager GEA Farm Technologies