The number of lambs surviving to sale is the main driver of profitability on most sheep farms. In at least South Otago and Southland this year farmers experienced a record scanning level with an average lift in the region of 10 – 15%. Several farmers I have worked with closely on sheep reproductive issues have had increases of 20 - 25%. However as we all know the south was hit by both a cold wet period pre-lamb meaning ewe feed was tight and also extremes of weather right at the height of lambing. The extent of the lamb losses will not be known for sure until the final tailing tallies are in and while I am still hopeful of at least an average tailing %, if not slightly above average there is no doubt that a lot of the extra potential has been lost. The increases in scanning levels that farmers are getting are all very well but not a lot will be gained if improvements in lamb survival, especially of multiple lambs cannot be achieved.
To calculate your lamb loss is quite simple. Work it out by:
Normal for NZ is between 15 - 19% - that is nearly 1 in 5 lambs born does not make it. A good target would less than 12 (even 10%) and there are some farmers who achieve these levels. If your loss is above 20 and there are plenty whose losses are between 25 – 30% there is definitely potential for improvement. Below is a list of factors affecting lamb survival with emphasis on those that farmers have an opportunity to influence.
1) Genetics – Sire/Breed Influence. Newborn lambs from some breeds are just innately more vigorous at birth. For example the “old traditional type” Romney lambs appear to be less vigorous at birth. Fortunately many breeders of modern Romney’s appear to have eliminated this as a problem. Mothering ability of ewes is also influenced by genetics. Do you know what your ram breeders scanning – tailing lamb loss is?
2) Lamb Birthweight. With the increase in multiples occurring as scanning % increases, one of the biggest problems is the lower lamb birthweights that result as these lambs succumb more easily in adverse conditions. Anything we can do to improve multiple lamb birthweights will improve lamb survival. There are two main areas where farmers have the opportunity to influence this.
· Feeding post mating. Ewes should be well fed (at least maintenance) through to day 60 (day 1 being the day the rams are put out). Any restriction of feeding in this period affects placental development, which in turn reduces lamb birthweights, particularly of multiples.
· Mid Pregnancy Shearing. Several trials on this have shown benefits, not only in terms of lamb survival because of higher birthweights but also improved ewe survival in the prelamb period. On average, provided the ewes can be adequately fed in the immediate post shearing period lamb birth weights increase by around 0.2 - 0.4kg when ewes are shorn between days 70 - 110.
As the % of multiples climbs the improvement in lamb survival that comes from the higher birthweights should far outweigh any possible increase in dystocia in single lambs.
3) Late Pregnancy Nutrition. The energy demands of a ewe carrying multiple lambs in the last 6 weeks, and in particular the last 4 weeks of pregnancy are astronomical. If she is unable to consume enough feed to provide that energy she utilises her own body fat as a source of energy. The extreme result of this is Sleepy Sickness. However there is a whole level of lamb loss that is influenced by the amount that a ewe needs to use her body fat as a source of energy without there being any sign of Sleepy Sickness. Mild under feeding of a twinning and even more a tripleting ewe coming into lambing can, because of toxins (ketones) released when fat is broken down to make up the energy deficit, depress lamb viability – some lambs may die prior to birth but more commonly lambs are born dull and less vigorous and hence are more likely to die soon after birth.
By feeding grain (barley, oats) or sheep nuts to multiple bearing ewes in the 4 weeks prelamb you will provide “concentrated energy” and help minimise this problem. A minimum of 200gms/head/day and preferably 300gms is needed to make a significant difference. Start off low (50gms/head) and gradually build up to the final amount over a seven day period. Triplet bearing ewes should be spread out for lambing as late as possible so that grain/nut feeding can continue as close to possible to the start of lambing. Grain/nuts are cheaper than bypass protein supplements and just as effective.
Also worth mentioning here under nutrition are:
· The usefulness of nitrogen application to “dig yourself out of a feed deficit hole”.
· If feed deficits at lambing or around 2 – 3 weeks post lambing when feed demand is at a maximum are the norm then a simple adjustment back of the lambing date can pay dividends and costs nothing. Later born lambs will invariably, because of superior ewe nutrition and milk production catch up and even pass their earlier born equivalents in terms of weaning weights.
In summary well fed flocks invariably have better lamb survival.
4) Trace Elements. The important ones here are Selenium, Iodine and Vitamin E – strictly speaking Vitamin E is not a trace element but it is appropriate to list it here.
· Selenium. Low Se levels can result in white muscle disease, which affects the heart muscle causing premature death. There are numerous ways of supplementing Se, farmers are aware of these and we see very little Se deficiency these days.
· Iodine. All ewes should receive some form of iodine supplementation prelamb. This is especially so with ewes grazed on brassicas as these contain chemicals (goitrogens), which effectively further lower iodine levels. Low iodine levels result in lambs that have reduced ability to regulate their basic metabolic rate – they are less vigorous, slow and succumb more easily in adverse conditions. Trials carried out by Massey University in 1997/98 showed variable, but some big responses in terms of lambing %. Currently there is not an effective test to determine stock iodine levels – just supplement! There are two ways to effectively supplement iodine.
i) Flexidine iodine injection. This lasts 12 months and is best given 6 weeks pre-tup.
ii) Oral Potassium Iodide. The correct dose (280mg) of this should be given 6 weeks pre-lamb when the foetuses thyroid glands are developing as this is when the iodine is needed. Some areas may need to dose at 8 and 4 weeks pre-lamb. Many farmers give Pot Iodide too late because of the convenience of giving it at the same time as 5 in 1 vaccination.
· Vitamin E. Low Vitamin E is similar in effect to low Se levels – it affects heart muscle and results in less vigorous lambs and/or premature death. In a trial in Wales lambs born to ewes given Vit E suckled an average of 17 minutes sooner than lambs born to control ewes – this could be the difference between life and death in colder weather. Brassicas in particular are effectively low in Vit. E and all ewes that have been on these should receive supplementation to improve lamb vigour at birth. The exact timing depends on the timing of the brassica grazing and also the method of iodine supplementation – contact your vet for specific advice for your situation.
It is somewhat premature at this stage to recommend routine Vit. E supplementation where ewes were all grass wintered – more hard data is needed before suggesting this. Work is currently underway in this area.
There are a number of products used for supplementing Vit E - e.g. Vitamix ADE, Livestock Survival Drench (otherwise known as LSD) & Solarvit. Beware - there are products about with very low levels of additives e.g.Vit E & iodine levels of about 4 - 5% of what is required so contact your vet for advice in this area.
5) Diseases. The most important ones directly impacting on lamb survival are:
- Salmonella Brandenburg
- Clostridial diseases
· Toxoplasmosis. The organism Toxoplasma gondii is possibly the most ubiquitous bug in the world infecting most species (including humans) and is present on all farms. It causes few problems in sheep unless the ewe is pregnant when it can cause, depending on the time of infection, early embryonic loss showing up as dry-dry ewes, abortions or weak full term lambs (in twins one can be affected and the other normal). Extensive trials have shown an average improvement of 3% in lambing % with the use of Toxovax. This is given once to the first lambers at least 6 weeks pre tup.
· Campylobacteriosis. Recent work has shown that abortions due to this are the tip of the iceberg – of greater importance is the birth of full term but weak lambs (sometimes one small twin) due to earlier placental damage in the ewe. Improvements in lambing % of an average of 5% have been shown where there have been no obvious Campy abortions. Where there have been previously diagnosed Campy abortions this rises to around 9%. There are two effective vaccines available – Campylovexin and Campyvax 3. Two doses 3 – 6 weeks apart pre-tup to the first lambers (hoggets or two-tooths) are required. If lambing hoggets a booster dose pre-tup as a two-tooth is recommended.
· S. Brandenburg. This vicious cause of ewe death and abortion has declined in incidence from its peak in 2000 but has shown it can still pack a punch. Case numbers increased slightly this year over last year. The disease’s effects can be reduced (but not eliminated) by vaccination with Salvexin + B. Contact your local vet to determine your “risk” and whether or not vaccination is appropriate.
· Clostridial Diseases. These can result in deaths from blood poisoning in ewes round lambing, Malignant Oedema (“jelly belly”) in newborn lambs and Tetanus and Pulpy Kidney from tailing onwards. Vaccinating with 5 in 1 should prevent these diseases however some farmer’s programme is not correct and deaths still occur. All ewes as well as being vaccinated annually 1 - 3 weeks pre-lamb must at some stage earlier, usually in their first summer/autumn, have received 2 doses of 5 in 1, 3 - 6 weeks apart otherwise antibody levels passed on to the lamb are insufficient.
In my opinion all sheep farmers who are serious about maximising their lamb production should be vaccinating with Toxovax, Campy and Clostridial 5 in 1 vaccines.
6) Physical Factors. Some paddocks have an inherently better lamb survival than others – multiples should be put in these and singles in the worst ones. Usually steeper paddocks have a higher death rate in twins due to “slippage” of the first born lamb down the slope however the reasons why one paddock may routinely achieve better or worse tailing % than another is often not clear.
With the recent bad weather experienced during lambing it has highlighted the fact that on many farms there is room for improvements in shelter provision. In particular “lower level” shelter is important and many farmers have made effective shelterbelts by incorporating toi-toi’s and flaxes into shelterbelts. Tussocks also provide very effective shelter (some of the best lamb survival figures I have seen come from farms with lots of tussocks) as do shelter belts of Leyland Cypresses, Western Red Cedars & Pittosporums - no doubt there are many other effective shelter options. Old pines & macrocarpas are invariably rather poor at shelter provision and can cause problems through the bare dirt “grubby” areas they create (see below under lamb diseases).
Worth mentioning here too is spreading the mating date of different mobs to spread the “weather risk” at lambing.
7) Triplet Scanning. As the % of triplets rises the benefits of actually scanning for triplets increase. These can then be run separately in the paddocks with the best feed prelamb and fed barley or nuts (see above). At lambing the general consensus seems to be that set stocking them in the best paddocks mixed with twins is preferable. Some farmers are rearing the third lamb from triplets artificially in rearing systems involving milk products and grain based supplements with weaning off milk at 4 – 5 weeks. Again contact your vet for more information on these systems.
8) Ewe Deaths. Space precludes detail on this but suffice to say the number of ewe deaths in the pre-lamb period has a major impact on lamb survival and attention to any problem areas can improve lamb survival. Common conditions include:
· Metabolic diseases
· Fading Johnes disease type conditions
9) Lamb Diseases/Deaths. Briefly, the most important conditions are:
· Arthritis – treat with 2 – 3mls of penicillin.
· Navel ill - this is a loose term and can include:
o Liver/lung abscesses - Both this and arthritis result from navel infections soon after birth or tailing wounds and it is probably the commonest cause of death on most farms once lambs are over a week or so of age. Try treating with penicillin at the first sign of ill health. Spraying navels with iodine (Vetadine) will help prevent this and arthritis. Try and avoid or modify “grubby areas”.
o Malignant oedema (Jelly Belly) – see above under Clostridial diseases.
· Watery Mouth – an oral infection from dirty conditions (“grubby shelter”, lamb warmers, mothering up pens etc) by E. coli, a common bacterium. It affects lambs up to 3 days of age and affected lambs go off their feed, salivate profusely and then develop bloated stomachs. Death can occur quickly within 6 – 8 hours. The most effective treatment for this condition is Spectrablock an oral antibiotic because it works quicker than injectable antibiotics.
· Ewe mastitis – If ewes have not been previously uddered, existing udder pathology can, most frustratingly result in lamb death from starvation. If you have not previously uddered ewes, up to 5% of ewes may well be affected and this can have a major impact on lamb survival as well as the amount of mothering up work at lambing time. Uddering should be carried out on ewes at least a month after weaning because a significant amount of mastitis can occur in the post weaning period and distension of the udder by milk makes detection of lesions any earlier more difficult. Farmers should be looking for:
o Hard lumps in the udder tissue.
o Saggy udders
o Burst healing and gangrenous udders – if relying on shearers these are likely to be the only ones they will detect.
o A cording/firmness in the centre of the teat canal – often missed by farmers.
o Firm swelling of one side from which pus can be expressed.
o Cut/missing teats.
Some normal udders can feel a bit lumpy - if you are not sure why not mark any you are suspicious of and get them double-checked by your vet.
· Starvation/Hypothermia – While not a “disease” in its own right, the end result of many of the above conditions (Low Se, Iodine & Vit E, Campy & Toxo infections, poor ewe nutrition etc) is starvation & hypothermia. Many farmers, because of the terrible weather this lambing will have seen publicity about a very effective, quick & cheap technique for reviving cold hungry lambs, involving intra-peritoneal injection of 20% Dextrose. Details on this should be available from your local veterinary clinic.
For further details or advice on the management of any of the above issues raised contact the sheep veterinarian(s) at your local veterinary clinic.
John. A. Smart B.V.Sc
Clutha Vets Animal Health Centre
P.O. Box 231
John. A. Smart B.V.Sc
Clutha Vets Animal Health Centre
P.O. Box 231
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