Converting Pallaton Raphno® to lamb liveweight gain

By Charlotte Westwood, Veterinary Nutritionist, PGG Wrightson Seeds

1. Set a grazing plan

A Raphno® grazing plan involves:

Paddock subdivision to set up a block rotation

Compared with set stocking, block rotational grazing systems offer benefits of:

• Better control over stocking rate and
• Reducing risk of Raphno DM yield ‘getting away’ on you if stocking rate is too low.
• Confining an area of Pallaton not ‘adequately’ under control to one to two blocks rather than the entire Raphno area.

Raphno dry matter yield (kgDM/ha)

• Knowing the DM yield of your Raphno crop helps refine your stocking rate calculations. Send crop samples away for DM% testing; Raphno contains slightly lower DM % than traditional brassicas. To find more information on measuring crops check out our Tools and Resources section in Knowledge Base: How to yield forage crops

Pick up a Raphno Road Cone from your rural retailer

• For lambs, once Raphno has reached the silver reflector strip on the Road Cone, you’re good to go – provided the crop has been in the ground at least 42 days. Raphno is treated with Ultrastrike® seed treatment which has a 42 day withholding period for all grazing stock classes. Simply put, that means stock must not graze Pallaton Raphno® until at least 42 days after planting.
• Target much lower post-grazing residuals (between 5cm to 10cm) than post-grazing residuals for forage rape.
• Once lambs start grazing the first block in your rotation, place the Raphno Road Cone into the last block of your rotation. Once the crop has reached the top of the Road Cone and beyond, it’ll be harder to manage feed quality using just lambs. Graze tall, stemmy crops with another stock class such as weaned ewes or cattle.
• If you haven’t got your Raphno® Road Cone talk to your local rural retailer to organise one for you.

2. Start grazing on time 

Don’t hold off grazing Raphno or you’ll risk the crop being too tall to be effectively utilised by lambs. 

• Start grazing once the crop has reached the bottom of the silver reflector strip on the Road Cone AND
• Observe the Ultrastrike® seed treatment 42 day withholding period for all grazing stock classes. The crop must have been in the ground at least 42 days before commencement of grazing.

3. Stocking rate calculations and monitoring

Raphno carries more lambs per hectare than traditional summer fed brassica crops as growth attributes are different from traditional brassicas.

Traditional summer brassicas

• Stocking rate calculations for traditional summer brassicas (Pasja II leafy turnip, Titan and Goliath forage rapes) are quite straightforward. Once traditional brassicas reach maturity, DM accumulation slows or stops. DM yield remains stable over the grazing period.  Major adjustments to stocking rate aren’t often needed during the first grazing.  

Stocking rate calculations for Raphno® are different from traditional brassicas

• Unlike the traditional summer brassicas, Raphno doesn’t stop growing and will not reach maturity meaning lambs should be stocked at a higher rate/ha than traditional brassicas. Expect Raphno to grow ‘under the feet’ of lambs, accumulating 30 to 50kgDM/ha/day (dryland) to more than 100kgDM/ha/day (summer safe or irrigated areas). We need to account for ongoing growth when setting our grazing management plan. The numbers of extra lambs needed depends on growth rates ‘under foot’. Stocking rates could be 30% or more lambs per hectare greater than for an equivalent crop of traditional summer brassicas at the same DM yield.

Check, check and check again

• Once grazing has commenced be prepared to re-evaluate. Have I got the stocking rate right or do I need to adjust stock numbers? Plan for more stock pressure if crop is getting too tall.   

Maintaining control

What if we delay start of grazing and/or don’t get our lamb stocking rate on Raphno quite right? 

• Crop “gets away” on you: Under-stocking of lambs increases risk of loss of control of your crop. If ongoing ‘growth under foot’ of the crop isn’t matched by lamb feed demand, crops grow rank and stemmy. If Raphno is much taller than the top of the cone and is developing a stem, don’t try using lambs to knock stem height down. Use another stock class that are better suited at that time of year e.g. weaned ewes, dry hoggets or cattle to eat the crop as lambs won’t do well on tall, stemmy crops. Lambs will enjoy Raphno® regrowth once another stock class has dealt to the stems.
• Lambs eat just green leaf: Low stocking rates allow lambs to browse through the crop, nibbling just green parts of leaves. Green leaf contains high levels of protein. Petiole (the white, central part of the leaf) contains lower levels of protein. Intake of dietary protein intake may be too high if lambs nibble just green leaf and no petiole. Once green leaf is gone and just petiole is left, intake of protein might be too low to support decent liveweight gains, especially if lambs eat just petiole for more than 3 to 4 days without access to another higher protein feed. Dietary protein intake is better balanced when lambs eat green leaf and petiole together. 
• Photosensitisation risk. Risk of primary photosensitisation (‘rape scald’) may be greater when lambs eat just green leaf (no petiole). We suspect the (unknown) agent responsible for photosensitisation may be concentrated in the green part of the leaf, not the petiole. Together with other photosensitisation prevention measures, encouraging lambs to eat green leaf and petiole together may reduce risk of photosensitisation.
• Very high stocking rate risks underfeeding of lambs and overgrazing of Raphno® and running out of crop earlier than expected.

4. Sort an animal health and nutritional plan for lambs

Prevention is better than a cure, so sort an animal health plan before the lambs start grazing.

Vaccinate lambs to reduce risk of clostridial diseases.

• Talk with your veterinarian about a vaccination program to avoid clostridial diseases, including ‘pulpy kidney’ (enterotoxaemia) and/or other vaccinations, anthelmintic or animal health treatments that your vet may recommend.

Avoid weaning and running lambs on crop on the same day

• If lambs are just weaned or bought in as store stock before starting onto Raphno, leave lambs to settle for a few days on pasture, then move lambs onto Raphno. Aim to avoid two or more major stressful events happening at once.

Transitioning from pasture to Raphno - good things take time

• Time is required to transition stock onto all forage brassicas – Raphno is no different from other brassicas – transitioning is needed for lambs moving from pasture to Raphno. It may take up 21 days for lambs to fully transition onto the crop and to be achieving high growth rates. Most transitioning is completed by the end of the second week on crop.

Novel forage / neophobia and a new environment

• Lambs need time to settle in the crop paddock – it’s a new environment and lambs need time to learn about tasting and grazing a new feed type. Brassicas taste very different to pasture. Stocking density of lambs on brassica crop is higher than on pasture. Lambs may need time to settle in and adapt to close social interactions with other lambs.

Rumen and liver adaptation

• As for all brassicas, the quality of Raphno is better than that of late spring/summer pasture. Time is needed for rumen microbes to adapt from a pasture-based fermentation to one able to effectively digest brassica. Time may also be needed for liver adaptation to more dietary protein when lambs transition from pasture to high protein summer crops.
• Time to transition to brassica might be shorter if lambs move from high quality summer pasture to brassica, or longer when lambs transition from poor quality pasture to brassica.

Fill lambs up with pasture before moving to Raphno for the first time

• Before running lambs onto Raphno for the first time, make sure lambs have a full gut of pasture. ‘Full’ lambs are less likely to gorge on crop, helping avoid nutritional and animal health challenges. Running lambs off crop to pasture each day for a few days may help with transitioning to crop, though care is needed to avoid pneumonia when regularly moving lambs in hot, dusty conditions.

Conserved forages for Raphno lambs?

• Baleage or hay can be offered to lambs on Raphno as a source of dietary fibre, especially during the transition phase. Wastage can be as issue as lambs may not have learnt about these feeds through previous feeding practice, thus often sleep on or play with hay, rather than eating these (expensive) feeds. If you plan to offer conserved feeds to lambs on crop, offer these feeds for 7-10 days before lambs go onto crop, preferably while lambs are still with the ewes.

Finding stock water

• Encourage lambs to find stock water by mowing or rolling crop allowing access by small lambs through taller crop, especially when water troughs are short /hard for lambs to find.