Supplementary feeding is often continued for too long on pastures where the correct amount of grass growth – 4-5cm – is easily capable of sustaining the nutritional needs of lactating ewes.
That is the warning from sheep advisers, who are keen to increase producers’ awareness of the financial benefits of monitoring and managing their swards this spring.
SRUC sheep specialist John Vipond says many sheep producers underestimate the high quality of spring grass and often feed ewes for too long.
“Once the sward height is 4-5cm and is being maintained at that level there should be no need to continue supplementary feeding.
“Research has shown any concentrates fed to ewes on grass that had reached a sward height of 4cm were simply replacing what the ewes could have obtained from the grazing.”
Mr Vipond says spring grass at the 4cm stage is capable of having about 11-12 ME and 18-20% crude protein.
“The first 12 weeks after lambing have the most influence on the profitability of lambs, so the value of grass should be exploited to the full and managed so that lamb growth continues unchecked.
“If ewes and lambs are turned out on to pasture and the grass isn’t properly monitored, it will either become overgrown and lose its quality or it won’t be sufficient to maintain their needs,” says Mr Vipond.
Calculating stocking rates is key to ensure ewes receive enough, says AHDB sheep scientist Liz Genever.
“We know ewes in the appropriate body condition score need no additional supplementation once grass is above 3cm,” says Dr Genever.
“So calculating the appropriate stocking rate is important to ensure supplementation requirements can be reduced.
“Ewes in early lactation will need to be offered more than 3% of their bodyweight in DM – once that calculation is known and grass cover is measured, stocking rate can be calculated.”
“We can assume a 70kg ewe in early lactation will require more than 2kg DM/day, so if grass growth is about 20kg DM/ha/day, about 10 ewes can be supported without eating into any of the reserves that have been built up.
“As grass growth increases into the spring, stocking rates can be increased to better match grass supply.”
Dr Genever says the number of ewes a field will vary depending on field size if it’s a set-stocked system.
“For most flocks the mob size is determined by handling facilities or the time taken to handle a group of ewes and lambs. Once groups have settled and lambs are older, smaller groups can be merged to start the rotation system.”
Tips for managing grass
- Measure grass ahead of lambing time
- Make a grazing plan
- Have confidence in 4-5cm of spring grass
- Make use of roots fed on pasture as a backup
A compressed sward stick will provide a measurement to enable kilogrammes of DM/ha to be assessed and make it easier to calculate demand.
“In periods of high grass growth, weekly measurement is important because the situation can change quickly. When sheep are in a rotation system, the ideal time spent in each paddocks is about three days.
“Any longer and there will be an adverse effect on new grass growing back.”
If farmers don’t have a sward stick or more sophisticated plate meters, there are other simplistic ways to measure and monitor, adds SAC sheep specialist Rhidian Jones.
He believes a box of Swan Vestas matches could have an important role to play in improving the profitability of sheep producers this year.
“Measuring and monitoring spring grass growth should be a high priority this spring and will signal precisely when there is no need to continue supplementary feeding.
“Although it’s an unlikely aid to managing grass, this matchbox measures 8cm long and 4.5cm wide and is perfect for giving farmers an idea of how much grass they have and checking for the all-important 4-5cm sward.
“If ewes and lambs are set-stocked, the width of the matchbox can be used as a guide to the continuous height required. In a rotational system, sheep should enter the field at the 8cm height and be removed at the 4cm height.”
Rotational grazing v set-stocked
Dr Genever says rotational grazing can be beneficial in controlling grass growth as the season progresses.
“The focus needs to be on assessing the demand to ensure the target of 4-5cm for set-stocking systems is maintained. Once the lambs get towards eight weeks there may be some advantage to moving them into a rotational system because it is a good way to control excess grass growth.
“It enables paddocks to be skipped, shut up and not grazed and cut for silage.”
Supplementary feeding in lactation
While high-quality spring grass is the “best-quality and cheapest feed available for ewes”, there are other options if growth is not meeting demand, says Mr Jones.
He says a ewe rearing twins needs about 36Mj of energy a day by the fourth week of her lactation and will require 3kg of dry matter to provide it.
Roots such as swedes or fodder beets fed on top of the pasture can provide a long-term back-up source of feed for ewes, he adds.
“Ewes can’t gorge on roots because they aren’t easy to eat. They are high in metabolisable energy but low in protein, which helps to use the excess protein in spring grass.”
“Grass that is more bulky and stemmy takes longer to go through the ewe and so intakes are reduced.
“Grass at 12ME is only going to allow ewes to capture about 12% of the protein available, but the high energy of roots will help them mop up the extra protein – about 5%.
“While systems such as forward creep grazing and leader/follower systems are being tried in some flocks, the most success has been achieved by those who are maintaining an efficient but simple system and moving ewes and lambs once or perhaps twice a week and minimising stress levels that can knock milk production.”
Case study: Matthew Blyth, Didling Farms, Sussex
Sussex-based lamb producer Matthew Blyth has achieved a significant increase in lamb weaning weights and reduced the amount of bought-in concentrates since measuring sward height became routine at Didling Farms.
In the past three years, average lamb weaning weights at 90 days have increased from 27.8kg to 33.3kg.
The annual pre-lambing purchase of 10t of concentrate used to only be enough to feed the main ewe flock – now it also feeds the farm’s 350 replacement hoggs.
Mr Blyth says measuring grass growth throughout the year is now a fundamental part of the business, which runs a flock of 1,050 Lleyn and Lleyn-cross ewes, all put to the Aberfield and Abermax tups.
“We have been measuring grass and making use of the data for about six years. We measure grass all through the winter using a sward stick to help us build a clear picture of how quickly the grass is growing.
“By early March we have enough data to work with so we can plan forward and know which fields we are going to turn out onto and which ewes will need feeding.”
Ewes come inside in mid-January, about 10 weeks ahead of lambing, and are fed a TMR mix. After lambing ewes are turned out on to fields that have been rested for three months.
By mid-January this year, the covers on fields that will be used for ewes and lambs were carrying 1,500-1,700kg of DM/ha – about 4-5cm.
If the farm’s five-year leys are not far enough advanced – and need more time to develop to provide sustained grazing – then ewes will initially be put on to fields with less grass and receive supplementary feed.
“If we leave the best leys alone and give them chance to develop, we know we won’t need to feed the ewes as heavily. If we can keep ewes and lambs off the best leys until they are carrying slightly more than 4-5cm of grass, we know we can get lambs away two weeks earlier.
“Even if we have ewes and lambs on an old ley and are feeding them, we find the lambs on the good leys will finish faster.”
All ewes and lambs are fed a compound ration for the first 10 days. “We feed at the rate of 0.25-0.5kg a head. But if the grass is there for the ewes, they soon tell us they don’t want any more concentrates.
“We used to budget to feed 10t of concentrates to ewes and lambs. Although we are now still ordering the same amount, it is also feeding our 350 replacement ewe lambs, so we are using less feed overall by making better use of the grass.”