Monday, 15 February 2010

Drenching Sheep and Weaning Lambs

On 7th February we herded the sheep from the Yabby Paddock into the yards, drafted the lambs from the ewes, drenched the ewes, released the ewes into the Deep Gully Paddock and retained the lambs in the yards overnight. On 8th February we drenched the lambs and released them into the Saddle Paddock. What follows is some of the background, observations and learnings from the overall exercise.

The Decision to Wean the Lambs

I conducted research to ascertain the best approach to separate ewes from their lambs (wean) to ensure that both were not checked. The range of recommendations was in the end mystifying due to the strength of diversity of views, which included:

  • Apply ‘weaning rings’ to the lambs and put the animals back with the ewes. These are small rubberised spiked clips that are placed into the nose of lambs (and calves). When the lamb attempts to drink from the ewe the latter finds the experience most uncomfortable and pushes the lamb away and in time weaning occurs. Advantage: No separation stress on either the ewe or lamb. Disadvantage: Cost of the rings, time and effort in applying them to the animals, failure rates and waste. Plus they don’t seem to be something that either the lamb or the ewe would appreciate experiencing!
  • Separate the whole mob into two halves, ensuring that each ewe / lamb set/s remain intact. Take the first half and draft off the lambs from the ewes. Then take the second half and do the same thing. Mix the lambs from the first half with the ewes from the second. Mix the lambs from the second half with the ewes from the first. Put both resultant mobs into separate paddocks. Advantage: Whilst the lambs no longer have access to their mothers to source milk (and are thus weaned) they are still able to receive education and increased survival rates by being with mature ewes. Disadvantage: Time and effort in sorting the mob, with a risk that the initial dividing of the mob into two halves is not ‘clean’ with not all lambs being separated from their mothers and are not weaned.
  • Separate the lambs from the ewes and put both (new) mobs in adjoining paddocks. Advantage: Reduced stress on both lambs and ewes as they can still interact indirectly along the common fence-line. Disadvantage: High risk that some lambs will get through the fence and re-unite with their mothers.
  • Separate the lambs from the ewes and put both (new) mobs in paddocks located a long way from each other. Advantage: Certainty of weaning occurring. Disadvantages: Separation stress and absence of mature sheep in the lamb mob to guide the lambs.

We selected the last option above based on our desire to reduce the possibility of having lambs reunite with their mothers. Some of the ewes had already weaned their lambs. The timing of our weaning was also some 3 to 8 weeks later than the industry norm; thus all of the lambs have had more coaching by mature sheep than might otherwise be the case.

I also sought information on how long lambs need to be separated from their mothers before the mother’s milk ‘dries up’ and the lambs on return can no longer receive milk. The answers varied widely, with some suggesting that the mother’s can still permit lambs to suckle (and will receive some milk) as long as 3 months after separation! We will want the ewe lamb portion to return to the ewes so that we can maintain a single mob after the wether portion has been sold.

We’ve been contemplating weaning the lambs from the ewes since before the end of 2009 but deferred taking this action given the benefits of maintaining one mob on the farm (time management, water management and maximising pasture production) and the rain we received over Christmas provided us with the bonus of certainty of having sufficient feed such that it was not necessary to reduce stock numbers. Against this, we do need to make sure that the ewes have sufficient time to increase body condition or fat score post weaning to either score 3 or score 2 on a rising plane of nutrition. Weaning removes the physiological drain on the ewes from producing milk allows them a better chance of gaining condition. This in turn increases the conception rate at joining provided they are not then over-weight. Added to this it really was time to wean the lambs as best practice suggests that having the lambs on their mother’s milk past 12-16 weeks adds little value to either the lambs as they get most of their nutrition requirements from the pasture. We are also getting close to the point of selling some lambs and having the lambs as a separate mob will mean we have fewer animals to work on during the selection process.

Fact Sheets on Fat Scoring and Conception Rates

Clink on the following link for a fact sheet on determining the fat scores of sheep and lambs:

Clink on the following link for a fact sheet on animal nutrition and fat score and the impact of conception rate:

The Decision to Drench

Part of the research I did on the subject of drenching sheep included whether it was possible / practical to incorporate a drench into the stock water; saving the time and physical effort of physically drenching each animal. We have been using a temporary water set-up including troughs and know roughly how much the mob drinks per day (especially on very hot and dry days). The basic logic of mixing drench in the water seemed sound in that as a rule of thumb the drench dosage rate/s and the amount of drinking water per day are both a (different) percentage of an animal’s body weight. I decided against such an approach on advice from a NSW DPI sheep internal parasites guru given several factors:

  • It is actually illegal, breaching labelling and product use requirements
  • It is impossible to control how much drench each animal receives
  • Following on from the above, animals that don’t drink on the chosen day (when the drench is mixed in with the water) may be the ones who need it the most, some might over-dose, and others may get such a low dose that it accelerates the rate of resistance in the parasites themselves
  • It is impossible to know whether the drench will react adversely to the tank, piping, trough or exposure to the elements

Given the impact of internal parasites (mainly worms of various sorts) can have on sheep generally we made the decision to drench all of the sheep (ewes and lambs) at the same time as weaning given we’d not drenched before and many people warned us that many lambs can be lost if not drenched at weaning. Ideally the drenching decision should be based on analysis of worm counts in faeces. Next time, maybe! It way well have been that the long rest periods we give our paddocks are such that there was no need to drench at all … but we figure it was ‘better to be safe than sorry’ – especially in the early stages of our sheep management learning journey.

Purchasing drench

When buying drench (and vaccines) it is necessary to have an idea of the body weight of the heavier animals in the mob. It is from this that the dosage rate is determined … and from this the volume of liquid that has to be purchased. Giving the animals a dose that exceeds the recommended ratio of drench / vaccine is less critical than applying a low dose. The latter fosters more rapid development of resistance (to the treatment) by the parasites.

In consultation with staff at our local rural merchant in Grenfell we bought two types of drench: both broad spectrum but the one for the lambs has added chemicals to address tape worms. Both (in our case) came in 5 litre containers which have a strap such that they become pack packs for the drenching. The set-up is slightly different to what I remember from my growing up days on the farm in that the pack is the opposite way up on ones back to what we used to do and this is facilitated through a tube that goes from the cap to the bottom of the container. From an OH&S perspective the ‘new way’ is no doubt safer as there is no risk of the cap coming off and releasing chemical down the back of the person doing the drenching.

We purchased a new drench gun to reduce the risk of equipment malfunction.

Herding the mob into the sheep yards

On Ochre Arch we do not have or use sheep dogs for a variety or reasons, the main one being that we practice both Low Stress Stock-handling and holistic planned grazing. It is very simple to move the animals from one paddock to another on foot; with Jan and me working together.

Getting the animals into the sheep yards proved to be not so simple and we’ve still much to learn. We got to a point where about ¾ of the mob went into the large holding pen on the eastern side of the yards but we just couldn’t get the remaining ¼ or so to go through the gate and given the length of time we continued our efforts it transpired that the whole mob came back out into the paddock releasing the pressure on the animals. (For those not familiar with Low Stress Stock-handling one of the ‘golden rules’ is that with herding animals under pressure is ‘the pressure will always be released’. Pressure is defined simplistically as an animal having something or someone within its ‘flight zone’ – which in human terms is very similar to ‘personal space’). It was then that I decided to try applying increased pressure to the mob at the entrance to the yards by using the 2-wheel motor bike. After quite some time and effort it became clear that this approach was simply not going to work. The mob was milling around outside the gate to the holding pen and none of the animals showed signs of going near the gate itself. We opted to revert to herding them on foot and after some patient effort involving actually reducing the pressure on the mob we got to a point where 2/3rds of the mob were in the holding yard. At that point we decided to shut the gate behind them and allow the other 1/3rd to stay in the paddock. We then moved those that were in the holding pen further into the main yards, and once that was done we then went back into the paddock, succeeded in herding the remainder into the holding pen (they could see the rest of the mob in the yards) and then moved them forward to be with the others in the main yard.

Lesson: Be both patient, not too ambitious and remember that increased pressure on the sheep is not necessarily the way to go. It did help us in getting the mob into the holding pen that it was well grassed.

Drafting the lambs from the ewes

I did the actual drafting given that at times this can be quite a physical exercise when two sheep come through together or in such quick succession that it proves necessary to stop them coming through to avoid animals ending up going into the unintended pen. Having said that, it’s not a big deal if a couple go the wrong way through the race as they can be individually caught and put where they belong once all of the drafting has been done.

Jan took on the task of hunting the mob into the drafting pen. This is not an easy task either and requires more patience and a more constant but reduced intensity of physical activity. Our drafting pen has two entry gates and thus can be accessed from two different pens in the yards. To begin with we were herding the animals from the northern / down-slope pen into the drafting pen but it was proving very slow. My instincts made me feel that the mob would flow better through the process if they were brought in from the southern / up-slope pen. We tried this and it made a huge difference, and substantially accelerated the process.

One curious observation was that it in the vast majority of cases the ewes were first to enter the drafting race itself, and very rare for a lamb to do so. Maybe this is because they have had several years of going through drafting races and know that the process itself actually leads to reduced stress once through the race.

Drenching the ewes

Our ewes are seriously big sheep making it a bit of a challenge for me to reach the heads of some in the drenching race. They are also strong and were fresh from the paddock. That said, we took our time and found that 25 or so fitted into the drenching race at a go. We were pleased to note that the ewes were in better condition than they looked from a distance.

One ewe was losing her wool. It was not due to lice and the wool was coming away in chunks from the skin. Subsequent discussion with a local long term sheep man suggests that this is not unusual and it is likely the animal at some point suffered a high fever but is now fully recovered.

One ewe was in absolutely prime condition. We assume that she may have lost her lamb/s at or shortly after birth. Its condition demonstrated both that sheep can do very well on our place and that the process of raising a lamb is physically very demanding.

An unexpected, annoying and in hindsight obvious learning was that as the drench level fell below about 1/3rd full air started being drawn into the drench gun. This was caused by the pack going from vertical to horizontal and beyond as I at times had to reach down low to the ground to lift the heads of some sheep that had found there way underneath others to reduce the stress levels. When this started occurring I took the pack off my back and Jan held it from the side of the pen. The good news was that no further problems with air getting into the gun occurred but the bad news was that it made it more awkward for me to do the drenching as the risk of an animal getting caught up in the tube from the pack to the drench gun increased. Lesson: If drenching on one’s own it may be necessary to set up some type of rig adjacent to the pen to hang the pack on to ensure that the number of doses calculated can in fact be dispensed.

One of Jan’s roles during the drenching process was to act as ‘spotter’ for me. When drenching it can be very difficult to remember which sheep have been drenched and which have not. Having a spotter is important to prevent no-dosing, and over-dosing and chemical wasting. Jan did a superb job of keeping track of drenched and to-be-drenched sheep.

The drench gun nozzle came loose at one point and had to be tightened. The drench given to the ewes was very milky in colour and quite thick. During cleaning (essentially flushing firstly water with detergent then just water through the gun) the flow through the gun ceased and I found it necessary to dismantle and separately clean the intake valve. It took a long time for the residual drench to be completely flushed from the gun.

We counted the ewes as each batch came out of the drenching race.

Releasing the ewes

Our experience at lamb marking was that ewes lingered near the yards (their lambs) when we let them out of the yards to gain access to feed while the remaining lambs were being progressively marked. We expected the same when we released the ewes into the Airstrip Paddock at weaning … before we took them on to the Deep Gully paddock. The reality was the total opposite. The ewes ‘took off’ and it is not an exaggeration to say that ‘not one of the ewes looked back’, even though the lambs were still within earshot and sight.

Leaving the lambs in the sheep yards overnight

It was never our intention to leave the lambs in the yards overnight but in the end we did so for several reasons: the activities we’d carried out to that point took longer than expected and we would not have had time to drench all the lambs before dark, we were unsure how difficult it would be to re-muster the lambs the next morning if we did let them out and we did want all of the drenching to be completed as soon as possible, I was tired and needed a rest, and we had heard that lambs in their own mob have a tendency to get over-excited and can trample each other … and by keeping them in overnight they might be less energetic than their mothers had been!

Drenching the lambs

It’s a bit hard to be certain but we think the lambs were less energetic as a result of being detained in the yards overnight than the ewes had been the day before. In any case, they worked well through the yards and we had no issues with trampling. Being smaller than the ewes we were able to fit around 60 in the drenching race each time.

The drench itself was clear. We had no equipment issues but did notice that the plastic barrel of the drench gun is now very slightly translucent rather than transparent from friction. Once again we experienced air being sucked into the gun when the container level was about 1/3rd full and resolved the issue in the same way as for the ewes.

We were curious to know the weight of the larger lambs as this information is a great help in the decision of when to sell – especially if we want to sell them as fat lambs rather than just for wool production. There are no sheep scales on Ochre Arch so we’d purchased a cheap set of bathroom scales for $10. The process for determining the weight of a lamb using these is simple but physical:

  • The person weighing the lamb/s finds his or her own current weight by stepping on the scales
  • Lamb is then caught and carried to the scales
  • The person with the lamb steps on the scales and the total weight is noted
  • It is then a simple calculation to determine the lamb’s weight, being weight at step 3 minus weight at step 1.

The lambs we weighed were in excess of 35 kg so we have subsequently decided to have a stock agent visit to develop a selling plan / program for the wethers and any other culls.

Jan counted the lambs as they came out of the drenching pen. From this we were then able to calculate the weaning percentage. Total number of lambs weaned divided by original number of ewes purchased as a percentage came in at 130 %. This was down from the 140 % marking percentage reflecting subsequent losses but is still very acceptable.

From a definition percentage: fertility is the ability of the ewes to get in lamb, and fecundity is the ability to rear the lambs. Both percentages need to be calculated based off the total number of ewes originally joined before we bought them rather than just the ones we purchased (which were all in lamb, with any non-pregnant ones having been sold post scanning). The revised figures then come in at:

  • Fertility rate = 97.4 %
  • Fecundity rate (to weaning) = 128.4 %

A small percentage of the ear tags applied during lamb marking was gone and a couple of lambs have had adverse reactions to their tags. More tags are now on order and will be applied at time of sale of the animals.

Additional treatment of some lambs

We noticed that several of the lambs had wool stain at the top and down the sides of their shoulders. The colour of the wool staple at that point was a bright oxidised copper. We’d not seen this before but deduced that the cause was moisture retention, and a possibly pre-cursor to fly strike. To reduce the risk of fly strike we separated these and the one or two others that had fly strike and treated them for fly strike after all of the lambs had been drenched. It has subsequently been confirmed to us that these wool stained lambs will be prone to fly strike and need to be culled from the mob.

Releasing the lambs

We released the lambs after treatment into the Saddle Paddock without incident.

Observations since the weaning took place

None of the lambs have found their way back to the ewes. Both the ewes and the lamb mobs have been silent; quite different to when they were together. When we drove the ute around the lambs we were particularly pleased to note how quiet they were … not stressed and with small flight zones reflecting the benefits of being handled in a low stress environment.

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