Heat detection

InCalf research shows it is likely that heat detection errors are limiting reproductive performance in around one-quarter of seasonal calving herds. Two mistakes that are commonly made when detecting heat are missing heats and inventing heats e.g. record the wrong cow ID.

It’s worth revisiting your heat detection strategy each season to ensure your team is ready to go by upskilling and refreshing their skills. The best heat detection programmes start with careful planning, good observation and the effective use of detection aids. Success also depends on your team's ability to distinguish and accurately interpret other signs of heat in cow behaviour.

Schedule regular times to monitor the how the programme is performing. This information is critical to spot trends early. A successful heat detection programme relies on monitoring and fine-tuning throughout the mating period.

Pre-mating heat detection

The period before mating begins is a great time to practise heat detection skills, check for cows that haven’t shown signs of heat, and anticipate when cows may next come on heat. Organise farm team training during this time so everyone is confident. The most experienced person can help support other team members in interpreting and recognising signs of heat.

Calculate your herd's pre-mating cycling rate, if cycling is less than 75 percent of the herd by 10 days before the planned start of mating, heat detection has not been fully effective and/or there are too many non-cyclers.

Planning pre-mating heat detection:

• Determine what date to tail paint your cows (35 days before mating start date) and what colour to use.
• Check tail-painted cows for rubbed tail paint at least twice weekly until MSD.
• Check to ensure all cows have an unbroken strip of paint throughout the monitoring period and repaint rubbed cows with a different colour paint (e.g. red).
• Determine when you will change colours (to easily identify late calvers).
• Determine who is responsible for monitoring which cow has cycled and what needs to be done with the information. Will it be recorded anywhere? Using mobile apps and some automated systems makes electronic data entry of herd mating events quick and easy.
• Confirm when you will make a decision regarding any non-cycling treatment and talk to your veterinarian.

The level of pre-mating heat activity is an early indicator of how fertile the herd is approaching AB. If the herd is meeting pre-mating cycling rate targets, then it is on track to achieve a 90 percent 3-week submission rate without non-cycling treatments. You should also expect a good conception rate, as 85 percent of cows will be first inseminated on their second or third heat post-calving if the pre-mating cycling rate is on target.

How to detect heats

Being able to interpret cow behaviour is critical when detecting cows on heat. The time when a cow is on heat is defined as the period during which a cow will stand to be ridden by her herd mates or a bull. It occurs every 18-24 days, averaging 21 days in non-pregnant cows and lasts on average 14-15 hours. This time can vary from 2 to 30 hours.

Every detected heat and successful insemination will result in an average increase of 25kg milksolids in production (21 days x 1.2kg milksolids = 25kg milksolids), and a longer recovery time between calving and mating, increasing the chances of more cows getting in calf the following season.

Observation of heats

The best time to spot cows on heat is about 2 hours after milking. This is when most heats will be visible. Before and after milkings in the paddock and in the race before milking starts are also good times to look for cows on heat. During a paddock check, check your cows quietly, pay particular attention to restless groups of cows.

Record the number of every cow detected on heat at each paddock check. Make note of suspicious cows who may be coming on soon. If several people are involved in heat detection, implement a system to ensure that all involved share their records. For example, a whiteboard at the dairy, texting, or use of apps.

Meet your AI tech

Before mating starts, meet with your technician and your farm team to confirm timing, plan who will meet the technician on the day, and what the process will be with drafted cows before and after they are inseminated. Identify whose responsibility it is to reapply tail paint and heat detection aids and when they should do so. This should occur no sooner than the following milking, but ideally the next day.

Submitting cows for AI

Record a "?" in your AB record whenever you inseminate a cow that might be on heat when you are not sure. Then look up any previous insemination heat records for that cow to help confirm her status.

Assessing heat detection using submission rate

Submission rates are a useful tool in assessing your current management of heat detection. Submission rates can be low for two reasons:

1. Your cows are showing heat normally, but you are not detecting them.
2. You have lots of ‘non-cyclers’ in your herd that are not showing heat normally.

Submission rates below trigger levels suggest action is required. Start by reviewing heat detection practices. Then look at other areas such as body condition, lameness, or other health issues. To assess heat detection efficiency, it is best to look at the 3-week submission rate of cows likely to be cycling normally. Early calved mature cows have every reason to be cycling normally and should be detected and submitted to AB in the first three weeks.