This episode was made in partnership with PGG Wrightson.

Getting crop transitions right is crucial, and can come down to three things: fibre, time and a nitrate test before putting stock in. Jason Leslie, PGG Wrightson Technical Expert in Animal Health, says the rumen needs at least 14 days, and up to 21 days to adjust when moving from pasture to brassica or bulb crops. Rushing that adjustment is the most common mistake he sees on farm.

“Transition is about setting that animal up to be able to take advantage of the investment in the new crop, but their gut system needs a bit of time to do that,” he says.

Fibre is the key tool through that window, he says. Hay, straw, baleage, silage or long standing vegetation all provide the effective fibre rumen bugs need to adjust to the new feed source and digest it efficiently.

“For a simple example, if the intake was going to be a total diet of 10 kgs of dry matter required by the animal, you wouldn’t want any more than one to one and a half kilograms on that first and second day of the new source.”

He says the total dry matter requirement for the stock class still needs to be met, whether for maintenance or live weight gain.

Nitrate toxicity is the risk that requires the most forward planning. Nitrogen fertiliser applied to crops can accumulate in the plant when conditions like dry weather or cloud cover slow active growth, he says.

“Hungry stock going onto toxic or high plants with high levels of nitrates is not a good recipe.”

He says when ruminants eat affected plants, nitrates bind oxygen in the red blood cells.

“The animals effectively start to suffocate slowly; they become staggery, weak, collapse, and that leads to death.”

Testing needs to happen at least a week before stock goes in. He says a laboratory wet chemistry test gives the most reliable result, as the quick colour-change test can be unreliable.

High nitrate levels do not necessarily mean a paddock cannot be grazed, he says. Fibre management and careful access limits apply, and stock class matters. For example, pregnant animals carry a greater risk and paddock allocation should reflect that.

Water access is non-negotiable throughout, he says. Temporary troughs need to move with the break as the paddock is consumed, and larger mobs may need multiple points of access.

Getting the planning right starts with knowing the crop, he says – yield, dry matter, feed quality and nitrate levels all need to be established before stock goes in.

“Don’t do it as you open and shut the gate, because you’re not going to get those answers that quickly.”

PGG Wrightson’s technical field representatives work with farmers on exactly that groundwork, from crop assessment through to transition planning and trace element supplementation for the stock class being grazed.

Make sure to contact PGG Wrightson to plan your crop and pasture requirements. You can find your local Technical Field Representative or store team at store.pggwrightson.co.nz

CountryWide CONNECT with Andy Thompson & Sarah Perriam-Lampp is our daily rural show livestreamed from 11am-1pm. Visit country-wide.co.nz on how to watch/listen or download the CountryWide CONNECT mobile app, available on Apple iOS and Android.