Grazing sheep on lucerne

This year, all paddocks will be grazed by triplet bearing mixed aged ewes and twin bearing ewe lambs mixed together (last year, twin-bearing ewe lambs grazed on lucerne whilst mixed aged ewes grazed on the comparison grass, clover and plantain mix).

This year, another grazing option has been added so there are now three comparisons:
1) Lucerne
2) A legume and herb rich sward mix suitable for GS4 option for environmental schemes
3) Grass, clover & herb mix

As lucerne doesn't hold any salt but is high in protein, sheep have access to rock salt and hay to help prevent bloat.

• Lamb weights assessed at roughly 100 days after lambing. Assumption of a weight gain of 10kg per ewe lamb on lucerne from the point of lambing to weaning and a loss of 10kg per mixed-age ewe on mixed ley.
• The farmer reported consistently strong growth and drought resilience in the lucerne paddocks. The lucerne grew whilst the grass fields had browned off, despite a 50% greater ewe stocking rate in the lucerne field.
• Lucerne’s fast regrowth means rotations can be reduced to 25 days prior to weaning.
• Lucerne caused increased photosensitivity and mortality from clostridial infections. The high protein nature of lucerne and rapid passage through the gut can cause bacteria to multiply.
• Constant access to roughage (high fibre) is important, as lucerne’s high protein levels can cause digestive upsets. Growing with larger grass margins, e.g. with cocksfoot, would reduce the need for fibre to be provided.
• Three times as many sheep on the diverse sward required anthelmintic treatment compared to the lucerne-fed sheep.

The lucerne field has shown consistent growth and drought resilience. It grew well over a very dry 10 week period this spring/summer, whilst other grass fields browned off, even though the sheep stocking rate is 50% higher for lucerne than for the grass.

For ewe lambs (young lambs which now have their own lambs in litters of two), typically one lamb is taken away and hand-reared whilst the other stays with the ewe lamb, to reduce the strain on the mother. In the lucerne field, both lambs are able to remain because lucerne has 4 times more protein than the other grasses and grows freely, making grazing to get the nutrition required for the day quicker and easier. "The ewe lambs are in the best condition that they've been in". The new lambs will grow up feeding only on lucerne. A hay rack is also set up in the field to be eaten by the sheep try to counteract the richness and bloating effects of lucerne.

This field lab was featured in BBC 4's Farming Today programme on 29th July.

The pregnancy scanning results of the sheep revealed higher fertility rates for the sheep fed on lucerne, linked to better weight gain and body condition scores.

Around an acre of the lucerne was affected by winter flooding and was under water for 2 weeks. It appears to be recovering but growth has been hampered compared to the rest of the lucerne.

Open session took place where farmers learnt from the experiences and research of Prof. Derrick Moot, who has years of experience researching lucerne grazing in dryland systems in New Zealand. He discussed how to design a grazing system to make the most of lucerne's excellent spring growth.

·   Key learnings on establishment and growth:

• Autumn is an important period for building nitrogen reserves in the root and recharging lucerne. Rest lucerne fields over the autumn when the plant is less productive to avoid killing it over a couple of years from overgrazing.
• Avoid glyphosate on new stands. It attaches to the sugars and kills the plant underground. Instead, do a hard graze so that there is no leaf left. If glyphosate is applied to leaves, the plant will translocate the chemical down to the roots and kill the lucerne.
• In Derrick's experience, lucerne even grows well on clay soils
• Plant lucerne where soils are deeper

Key messages on livestock grazing preferences, health and management:

• Livestock prefer 70% legume and 30% grass. Create access to pasture so that the animals can move freely between the two areas ('landscape farming')
• An ideal entry point for lambs to start feeding on lucerne is when lucerne is 30cm in height
• If grazing with cattle, graze to similar heights but beware that cattle are more at risk of the health implications from overgrazing, e.g. bloat, red gut.
• Leave out salt blocks for livestock. Lucerne is sodium deficient, high quality feed, meaning there is a higher risk of clostridial bacteria.
• Don't put livestock on lucerne with leaf spot if they're about to go into mating. The high levels of coumestrol hormone will trick their bodies into believing they are pregnant so decreases the ovulation rate and therefore the conception and lambing rates. It doesn't cause any post mating problems.
• It is more difficult to avoid issues of photosensitivity livestock will need to be removed from the lucerne fields entirely.

Nitrate poisoning can very easily kill. Be careful about flushes after sudden rainfall. Heavy rainfall after drought causes a sudden uptake of nitrate in the plant. If conditions are dull (no sun), there is not sufficient energy to convert nitrates into proteins. It is important to wait until the sun comes out, then graze.

One of the farmers' observations so far: "We have just started lambing on the lucerne seems to be no problems so fair with lambs popping out and to their feet as normal, also no visible signs of any adverse affects on the ewes and plenty of milk about... so all is well (finger crossed). The ewes have done a nice job of taking out most of the annual weeds and the cover is still building". Further measurements to come...

Blood samples have been taken from sheep fed on lucerne and those in the control group (no lucerne). The samples will provide data on energy, protein and trace elements - cobalt and selenium.