By Dr Clive Dalton
Measuring feed (pasture)
- This is where feeding sheep really starts, as pasture is the main feed you’ll be offering your flock.
- You have to be able to look at a paddock and estimate how much feed is growing in it so you can work out how many “grazing days” there are for the flock.
- It’s simply a question of when do you shift the sheep. But it’s not simple.
- Realise that not all of what you see in a “pasture” is going to be nutritious feed.
- If you look at an area of sward you’ll find grasses (some good and some not-so-good), clovers (usually all good), a wide range of weeds, bare ground and dung patches.
- The last two do nothing to make money from sheep, and the weeds may even stop grass and clover growing.
- Learn to think in terms of dry matter per hectare (DM/ha) all the time. So when you look at a paddock and you see “what’s on offer” to the stock, it will be in kg of DM/ha.
- If you want to know what is growing each day, think of kg of DM per hectare per day (kg DM/ha/day).
- So forget about the old acres and visualize hectares all the time and the DM that is there, and what extra you are getting each day, and of course how much of that DM/ha the stock will eat each day, how much they will leave and how much they will waste.
- This is the first part of “feed budgeting” where you see if the feed on the farm expressed in DM will meet the needs of the stock. You can do this in three ways:
- This is accurate but tedious.
- Make a metal square (as wood breaks easily) with sides measuring 0.5m. Making the sides 1m long is too big to work with.
- The area of this square will be 0.25m. (Remember half x half = a quarter). There are 10,000m² in a hectare so multiply the 0.25m by 40,000 to get the weight of pasture from your 0.25 square metre frame on a hectare.
- Throw this square at random (at least 5-6 times) walking across the paddock and cut the pasture growing inside it with garden shears or old sheep shears. The more samples the better but time will limit what you can do as it’s so time consuming.
- Weigh the wet pasture.
- Mix it up well and take a small sample and weigh it.
- Put this sample of feed into an oven at about 100°C for about an hour, or microwave on defrost for 5 minutes or until it stops losing weight.
- Weigh the sample when it is completely dry.
- Then calculate the (Dry weight/Wet weight) x (100/1). This is DM%.
- Here you use a ruler to measure average pasture height across the paddock.
- It’s not a high-precision method.
- Rulers are produced by commercial companies e.g. fertiliser manufacturers.
- Equations have been worked out relating pasture height with DM/ha for spring, late spring, summer, autumn and winter.
- The ruler shows kg DM/ha.
- Go around the farm with a plate meter which are commercially available.
- It works on the simple principle of pressing down on the “pasture mass” and from using equations comparing the pressure with the cut & dry results, you can estimate kg DM/ha. The equations vary for the time of year but all these are in the instructions, or you can get them from a farm consultant or veterinarian.
- If you buy plate meter, pay the extra money for one with a small computer on it to save all the tedious calculations.
- Don’t take their readings as gospel – and never expect two operators in the same paddock to get the same readings. It’s not that precise an estimate.
- Go around the farm with an electronic probe.
- This does the same job as a plate meter but works off electrical impulses produced by the pasture mass.
- Electronic equipment doesn’t like wet weather.
- It’s more sensitive and less robust than a plate meter and it’s also more expensive.
- This is where you walk the paddock and estimate what’s growing by eye.
- The big advantage is that it’s fast and you have no gear to carry around.
- Accuracy depends on your experience – and as you gain more. you can become very accurate, or as accurate as you ever need to be.
- The best way is to learn is from other farmers, preferably at a group discussions when you can see how folk vary in their estimates.
- Have frequent checks with other people, or against the plate meter and probe. Or if you can face the tedium, cut and dry a few samples every now and again.
- This unit built on skis is fitted behind an ATV (quad bike) and travels at 15km/hour taking readings hundreds of times a second using a swath width of 12 m. This produces around 100,000 readings per hectare.
- It’s big advantage is speed and the large number of readings it can take to iron out variation across the pasture when only a few readings are taken.
- Realise that using these methods to estimate pasture growth, (other than by the tedious method 1) will show great variation, so use your eyes to constantly check what is going on. You’ll soon see if you got things wrong, such as when you calculated the paddock should last the sheep 3 days and they eat it out in one!
- When you walk the farm to estimate pasture- walk the whole farm! Don’t walk (or ride) into the gateway and base your estimate on a quick circuit. Walk the paddock on a diagonal and if there are any areas that you know have different soils or not as well drained, go and estimate them separately to add into the total.
- Most sheep farmers are going to end up using eye assessment (which is mainly pasture length) to estimate feed cover so this would be the best skill to aim for.
Practical exercise
Question: How many grazing days will there be in a 5 ha paddock for 1500 ewes?
Here’s what you do:
- Work everything out on per hectare basis.
- Assess what the pasture cover is – assume it’s 4cm long and 1400kg DM/ha.
- Decide what the residual will be after the sheep come out of the paddock – assume 800kg DM/ha.
- So the sheep will eat 1400-800 = 600kg DM/ha.
- On the 5 ha paddock the total feed is 5 x 600 = 3000 kg DM.
- So 3000 kg DM for 1500 ewes will last 3000/1500 = 2 grazing days.
- If you know that pasture is going to grow significantly during the two days, then you can add that in to the calculation.
Knowing how pasture grows on your farm
- Knowing how much feed your farm will grow is the key to profit. When you start off you won’t have any idea so ask a consultant or local farmer who has been monitoring feed for a while and use their figures. Or they may have district averages as shown in Table below.
- Once you have been monitoring your own farm for a while, this information will be the most reliable.
- The grass growth pattern will show a high peak in the spring, then a drop off till mid summer with a bit of an autumn flush before the winter period of slow and low, and even no growth.
Key points from the table
- Soil fertility has a massive impact on pasture growth and so does rainfall.
- There can be enormous seasonal variation around these averages.
How much feed do sheep need?
Using pasture length information.
The table below shows some information as a general guide to feeding sheep at different production levels and ages.
Key points from the table
- Note these are minimum values so always aim to exceed them in practice.
- When pastures are short and don’t exceed 5 cm in length they would generally be green, leafy and hence have high protein and energy. The challenge is to keep them like this all the time.
- The exception would be in summer when it gets dry and there was a lot of dead litter on the surface that rots away quickly with the first autumn rains.
- The ewe in late pregnancy and when suckling lambs needs the very best of pasture to meet her daily DM needs.
- Growing lambs need good pasture to allow good growth and development. The figures in the table should be minimum levels.
- The same applies to hoggets – they need to be kept growing on good feed levels.
The feed needed for maintenance is based on live weight and this is shown in table below along with what happens when feed quality varies.
Key points from the table
- Poor quality pasture has 25%+ dead material.
- Average quality pasture is green leafy.
- Good quality pasture is legume dominant.
- For extra 50g/day gain (feed = 10 ME) add 30% to maintenance.
- For extra 100g/day gain (feed = 10ME) add 100% to maintenance.
- So a good round figure to remember is that a ewe need to eat 1.0 – 1.3 kg of DM/head/day of good to average quality feed to maintain herself.
- This can also be defined as holding her at a condition score of between 2.5 – 3.5. This should be your management aim during the summer period after her lambs are weaned.
Feeding for flushing and joining
- Flushing is the ancient practice of feeding ewes on a “rising plane of nutrition” 2-3 weeks before the ram goes out, and a couple of weeks during joining to encourage better ovulation rates.
- What is a rising plane? Research shows that gains of 0.5 -1.0 kg/head/week can be useful targets, but it depends so much on the actual weight the ewes are at to start with.
- Good target (minimal) weights for ewes are:
- Pre-mating 53kg and Condition Score of 3-4.
- Mating – 57kg for 2-tooths and 60kg for mixed-age ewes.
- Ram removal – 55kg.
- Ewes can gain 0.5-1.0 kg liveweight during the first few weeks of joining if good green leafy feed is available. Ideally they should be going into 5-6cm of pasture (2200kg DM/ha) and leaving 3cm pasture (1500kg DM/ha).
- This is not often possible on hill country, especially in dry autumns when 2-3cm-long feed would be more likely to be available.
- Good feeding in the first half of pregnancy is vital for good placental growth, and if this is neglected, it cannot be put right by good feeding in the second half of pregnancy.
- This means a good pasture cover for lambing is around 1200–1300kg DM/ha but for really high production 1400–1500kg DM/ha should be the target.
- The other target is a minimum of Condition Score 3 for lambing.
- It’s a good aim to feed ewes 3 weeks before lambing on the same feeding level as they will get as soon as they have lambed.
- The table below shows how feeding levels needed at different stages of pregnancy.
Key points from the table
- Clearly the ewe’s feeding needs go up rapidly as the ewe approaches full term.
- These values assume the ewe’s single lamb is 4kg birth weight, and the twins would be around double this.
- For triplets add an extra 75% to the twin values.
Weight of uterus and lambs during pregnancy
The scales only tell you the total weight of a ewe which includes what’s inside her, so as the lamb/lambs get heavier, the ewe could be getting very skinny and losing weight rapidly. This is where condition scoring is a good guide to her state of health. The table shows some general figures used to account for the uterus full of lambs and fluids called the “gravid” uterus.
Feeding growing sheep (lambs)
- Young growing sheep are the ones that really need plenty of high quality feed that includes all the important nutrients.
- Lamb growth in the first 4-6 weeks after birth is based mainly on the ewe’s milk supply, but after that lambs start to build up their intake from pasture.
- Ideal pasture should be short, leafy and high in protein and energy.
How fast can lambs grow?
- From birth to weaning lambs can grow at very variable rates, mainly related to the ewe’s milk supply and the competition among litter mates for it.
- Singles can average from 200-300g/day, twins from 200-250g/day and triplets around 170g/day. Consider 150g/day as a minimum growth rate target.
- Some phenomenal gains well above these levels have been recorded such as 500-600g/day when everything is right, but these are exceptional and were for super-fed ewes with very high milk production.
- As a general guide, each extra 100kg DM/ha of pasture cover will produce about 11g/head/day of lamb live weight.
- If lambs are growing fast, they are converting their feed efficiently.
- Because of the varying growth rates from birth to weaning, weaning weights can vary enormously too e.g. 21-46kg.
- A good average weaning weight target is 28kg with a target for all lambs to exceed 25kg, but many hill country lambs don’t get near this and are around 13-15kg, so they have a long struggle ahead of them.
- Aim for ewe lambs to be 29kg in November, 35kg by March, and 40kg by May (South Island dates would be one month later).
- Growth rates after weaning through the summer average around 125g/day, but after the autumn flush and into winter, lambs should average 150g/day.
Feed needs for growing lambs
The table below shows the different needs of lambs that grow at different rates.
Key points from the table
- Fast-growing lambs are more efficient converters of pasture into meat.
- They reach target weights faster and eat less getting there.
The table below makes a similar point showing the daily energy (ME) requirements of lambs (male and female) at different weights growing at different rates.
Key points from the table
- Once lambs start to pile on the weight, their energy needs really go up fast.
- Use the ready reckoner if you want to convert these ME values to DM.
Feeding growing sheep (hoggets)
- Hoggets are the future flock ewes, and again need special treatment.
- If they are mated, then they need an even higher feeding level.
- The table below shows some ME feed requirements for hoggets.
Feeding lactating ewes
- A lactating ewe, especially one suckling multiple lambs, is pouring out energy, which she may struggle to take in through her diet.
- In the early stages of lactation, like the dairy cow she’s in “negative nutritional balance” which can affect her health unless she is given extra concentrate feed which is not a common practice in New Zealand.
- The table below shows the high levels of energy (ME) needed during lactation for ewes of different weights.
The table below is the same information if you want it expressed as Dry Matter.
Key points from the tables
- Ewes suckling twins need more feed than those suckling singles, right up to week 9 of lactation. Peak lactation is around week 4.
- As ewes increase in weight, they need more feed too.
- Losing weight has important implications – it needs to be avoided wherever possible.
- Each kg of ewe weight gained will need an extra 65 ME units.
- Being realistic, you would never be able to feed ewes on pasture, and even with grain supplements to gain weight during lactation. The aim is to avoid massive losses. It all goes back to having ewes in top order at mating and coming up to lambing so they can stand the negative-balance time with minimal impact.
- A good ewe is one that can lose weight during lactation because she is milking well and using her body reserves to good effect. Such a ewe has the capacity to regain weight quickly later.
How to provide these feeding levels?
- For lambing most farmers provide at least 1200kg DM/ha for ewes with singles, and 1500kg DM/ha for ewes with multiples.
- Ewes with twins eat about 25% more than ewes with singles in a 100 day lactation.
- During lactation, pasture covers should not drop below 1200kg DM/ha as quality also drops, and the ewes have to work too hard to get enough to eat.
- Any paddock that gets beyond 1800 kg DM/ha is too long for sheep and should be fed to cattle or taken out of the rotation for silage or hay.
At the risk of more confusion, for those who prefer to think of a sheep’s requirements in DM/head/day in preference to ME intake/head/day, here’s a ready reckoner to tell you how much DM the sheep will have to eat, if you know how much ME it needs/day, and the ME concentration of the feed it is offered.
Key points from the table
- You may have to look at this table for some time before you can follow it with ease!
- The figures in the main cells are all in DM/head/day.
- Decide what the ME/head/day needs are, then select the feed density level and read off the DM/head/day.
- So if a sheep needs 12 ME units/day and you offer poor hay at 8 ME units/kg of DM, the total DM the sheep will have to eat is 1.5kg DM/head/day.
General points on supplementary feeding
- Sheep have to learn to eat supplements and the best way to teach them is to feed it to them as lambs with their mothers before weaning. This assumes their mothers have learned to eat it too.
- Hay for sheep must be of good quality – i.e. green and leafy. When fed long stalky hay sheep only eat parts of it and waste the rest.
- Silage again must be good quality for sheep (over 18% Crude Protein) if you want them to clean it up.
- Don’t overfeed sheep with silage or hay as they are very selective and will waste much of it.
- Brassica crops such as rape or kale have high ME values but low DM, so they are very bulky feeds. It may take some time before sheep start to eat crops like rape and kale. These are good feeds for mid pregnancy.
- Green turnips and swedes are similarly ideal mid-pregnancy feed. Sheep like turnips, eating the tops first before chewing into the bowls, but despite their good ME values these root crops are low in DM so are very bulky feeds.
- Hoggets that are changing their teeth may have problems eating the bowls of root crops.
- Grain is high energy and can be fed throughout a ewe’s entire pregnancy if it can be justified on cost. The cost of DM in grain is often four times that of silage and six times good pasture.
- The important rule is that when you change the diets of sheep (or any ruminant), you should do it slowly over a period of at least 4-5 days to allow the rumen micro-organisms time to readjust to the new diet.
- The table below shows the feed value of different feeds suitable for sheep.
Are you lost?
Don’t be surprised if you feel this is all too complicated! Don’t panic and just use the tables for reference. As stated at the start of the chapter – it’s all about knowing when to open the gate to let the sheep into the next paddock and making sure they’ll benefit from the move! If they rarely do this – consider the next question.
Have you got too many stock?
This question can keep nagging at you and it’s like asking how long is a piece of string? If you are constantly running out of feed, even in the spring flush, then the chances are very high that you have too many stock.
You are “overstocked” or have too high a “stocking rate”. These are all farming terms to describe the situation that needs fixing before you run into major feed and animal welfare problems. So it’s a good idea to see what your stocking rate is, and to do this you can use the old (if not ancient) system of Stock Units (SUs).
Stock Units
- The idea behind Stock Units is to compare all the stock on the farm on a similar basis so that you can get some overall measure of the feed requirements.
- The theory is sound enough, but it’s an old system and is of little if any value on today’s farms. But it’s still used for beef and sheep farms by vendors and land agents, where the farm is described as carrying or wintering a given number of stock units. Farm workers and managers’ jobs are also described using stock units.
- A SU is also called a Ewe Equivalent (EE) as the base used is one 55kg breeding ewe rearing a single lamb needing approximately 520-550kg DM from good quality pasture which includes what the lamb will eat up to weaning at 3½ months.
- You may also see the term LSU or Livestock Units used.
- A farm’s carrying capacity or stocking rate (SR) is expressed as the number of SUs carried on 1 July so it’s the number of stock that will be wintered.
- If you can farm your stock through the winter, then the rest of the year should be no problem.
So where do you go from here?
Often you don’t get very far and the exercise seems a bit academic! When you ask someone who is supposed to know the answer – they invariably start off by saying - “Well it all depends!”
Here’s the drill. Once you have converted all stock on the farm into SUs, and then divided by the number of hectares, then you’ll know your SU/ha. But how do you know if it’s too high or too low, or what’s the ideal for your farm? This is when you should talk to local farmers, neighbours or farm consultants – but don’t be surprised if they are scared to commit themselves. If you hear of a farm successfully running 12 SU/ha then it must be a good farm as this is at the high end.
In practice, go back and analyse what happened in the dead of winter. If you were in deep trouble then reduce your overall stocking rate. Don’t judge your stocking rate in the spring flush! Smart operators know what live weight of stock they carry per hectare and this makes a lot more sense if you can work it out. Live weight per hectare will be a lot more help when you do a feed budget.
Disclaimer This material is provided in good faith for information purposes only, and the author does not accept any liability to any person for actions taken as a result of the information or advice (or the use of such information or advice) provided in these pages.
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