Forage for Knowledge

The long-range forecast looks unsettled for a week, followed by a return to warm temperatures.

What that means on your farm will vary. You might get a good mix of warmth and moisture, which drives growth. Alternatively, you could face heat and limited rainfall.

If conditions turn dry, remember that growth rate dictates round length. If growth slows, extend your grazing round to match growth.

You may need to add supplement, protect average cover, and look after the plant. This helps make sure the grass can respond straight away, when the rain comes.

Learn more about dry weather management

Managing heading in late perennial ryegrass

We’re now heading towards the late heading stage for perennial ryegrass.

Where moisture is good and growth rates are 60 and above, aim for a 21-day round.

98% of tillers will only head once, meaning that if you graze while the seed head is still in the sheaf it's grazed and will not head again.

The 21-day round gets through the platform and minimises the slight drop in quality around heading. Once the head has gone the plant will return to its vegetative leaf and quality. 

Where conditions are dry and growth is slow:

• Round length should still reflect growth rate
• Use pre- and post-mowing to clear any seed heads
• Focus on the first three weeks of June to reboot the plant for when rain arrives

It’s always better to let cows do the work. However, for mistakes and oddities, a small investment in tractor time can improve utilisation later.

Growth rates and what to expect next

Reported growth rates across the country range from 38 to 121, with most farms in the 60s to 70s.

This data reflects growth up to early this week, so it doesn’t yet show the effect of the recent high temperatures. The variation is largely due to moisture availability.

Growth is likely to fall this week, as ryegrass doesn’t perform well in high temperatures.

On a farm visit earlier in the week:

• Light soils and low rainfall were limiting factors
• 90% of the platform was in herbal mixes
• Virtually no nitrogen had been applied
• Expected to be returning to graze a paddock in 28 days on a paddock grazed two days earlier

Heat stress in cows

Recent temperatures have been stressful for forage growth and especially for livestock.

On the same farm, a weather station recorded 28.9°C at 11:30am and 63% humidity. This placed cows on the border between moderate and severe heat stress.

Interestingly, at 7:00am the day before, humidity was 90% and dropped to 40% in the afternoon.

While lower humidity reduces stress, rising temperatures offset this benefit. Overall, cows were under consistent heat stress throughout the day.

The cows were in a paddock with access to shade and water, and panting scores were assessed.

There were five groups monitoring different cows. Scores were between 1 and 2, indicating mild to moderate heat stress. This is likely similar across many farms currently.

Heat stress affects:

• Dry matter intake
• Body condition
• Fertility
• Milk production

It’s both a welfare and profitability issue.

Practical steps to reduce heat stress

Below are a few things to consider. This is nowhere near exhaustive, so it’s worth reviewing your own system in more detail.

• Ensure good access to water – 50% of intake happens within three hours after milking. Provide large, well-placed water troughs without disrupting cow flow
• Use fans in collecting yards. If in doubt, stand in the yard with cows for five minutes – comfortable?
• If your sheds are airy, high enough, and have a breeze through, bring cows in between 11:00am and 3:00pm. Feed should be minimal during this period
• Offer any supplemental feed in the evening. Cows eat quickly in cooler conditions, and rumination produces heat
• Use paddocks with airflow. Higher ground often benefits from more breeze than valley fields

Learn more about managing cattle in hot weather

Plan ahead for summer

We’re only at the start of summer, and the last few days are a reminder of what may lie ahead.

Now is the time to plan and put measures in place to reduce the impact of heat stress.