Learning about Agriculture: 3. Lambs prancing in the fields.

Sheep are as much of a symbol of Wales as the dragon on our flag and so in this blog I’m going to be looking at all things sheep. Here we go.

Selective breeding is commonly used in agriculture to increase profitability, and sheep are no exception. Advantageous traits can be identified in parents so that these traits can be passes down to offspring, which will aid profitability and improve herd health. These traits are identified through EBVs (Estimated Breeding Values) for rams, and Body Condition Scores (BCS) for ewes. EBVs are used to predict the breeding outcome for that particular ram, for example the EBV for fat depth is an indicator of whether the carcase will likely be lean. These however, are not the only factors that are used – the others being physical characteristics checked through the 5T’s – check toes, teeth, testicles, tone (BCS), and teat.  For ewes, BCS is the only method used and a score between 1 (thin) to 5 (fat) is given to each individual ewe and requires no specialized equipment or history unlike the EBVs which require CT scans. It looks quite easy to do but I can imagine it would take a while to differentiate between the five stages.  You just place your hand on the back of the sheep and feel for the transverse and spinous processes – if the ‘backbone’ feels rounded and the bone on either side is detected with hard pressure then there is plenty of muscle and good fat covering, which would give a value of 3.  This value however, is dependent on the type of grazing, with hill ewes requiring a target of 2.5 as compared to lowland ewes with 3.5 and should be maintained for a month before tupping (mating)[i].

Maybe it’s just me, and that I don’t know anything about pregnancy, but I feel like farmers have got this pregnancy stuff down. The ADHB Better Returns Program has detailed guidance on each stage including a calendar on when everything happens. Its so good that I feel like I could give it a go and not completely mess it up. Some of the things mentioned are common sense, like to reduce stress for a month after tupping to allow attachment of the embryo, but others require knowledge of crops.

Physiological systems are designed to metabolize and convert chemicals, and as a student of pharmacy, we study how some compounds/drugs can be effective at treating a disease. Not all drugs are effective and so their structure is modified to aid its effectiveness within the body. For example, aspirin is a prodrug, a modified version of salicylic acid, which is the painkiller. As a drug salicylic acid has a serious side effect in that it causes gastric irritation. So, aspirin enters your system, and is metabolized to the useful compound, and your stomach thanks you for it. Clover is both advantageous for land management as it is a legume – plants which undergo nitrogen fixation, reducing the need for expensive artificial fertilizers; and a good source of protein for grazing animals. Red clover contains the phytoestrogen Formononetin which has no oestrogenic activity, but after rumic metabolism it is converted to equol. Equol is an oestrogen agonist meaning that it is able to bind to oestrogen receptors, mimicking its action. Oestrogen receptors are found in a multitude of organs in the body, which explains its anabolic effect which is beneficial in stimulating muscle growth. However, depending on lengths of grazing, it can cause infertility, which may be permanent in ewes. Reduced conception rates are due to changes in the cervix such as reduced viscosity of the cervical mucus, but of those that carry, it can result in conditions such as a prolapsed uterus[ii].

Like humans, sheep undergo ultrasound scans to determine pregnancy, which normally occurs at around 80-100 days post-tupping, and allows a series of decisions to be made regarding both farm management and animal welfare. Dry sheep (those not carrying lambs) can be sold, those with multiple births given more feed.  It can also help detect problems on the farm, for example if there are considerable losses between scanning and birth then ewes may be diseased and an investigation needs to be made.

With 75% of foetal growth occurring in late pregnancy diet changes need to be implemented to accommodate the ewe’s increased nutrient requirements[iii]. These changes include an increase in protein intake and increased calcium which is needed for both lamb skeletal formation and milk.

I have never been involved in the lambing season but I do know from other family member that have sheep that it can be a stressful time, with the need to be up and ‘on call’ so to say to aid with difficult deliveries and to make sure that newborns feed properly.  With the average flock size in Wales 362 for breeding ewes, it equates to quite a few deliveries[iv].

As cute as lambs are, they have high mortality rates at around 15% with 49% of lamb losses occur in the first 48 hours of birth[v]and so targeting each cause of mortality can reduce lambing mortality.  Each of these factors, which can be approached individually play an interconnected role in lamb welfare. For example, maternal body mass is a key indicator of lamb birth weight; and a low birth weight would mean that the lambs are weaker and so unable to suckle on the colostrum, leading to a reduction in both energy intake and immunity compared to those of higher birth weights[vi].

Lambs initially feed on colostrum (first milk produced by ewe) and this milk allows for passive immunity due to its high content of maternal immunoglobulin. It was found that pre-lambing vaccinations reduced lambing mortality[vii]and it would be interesting to see the Ig concentrations found in colostrum of vaccinated ewes vs those unvaccinated. Research for another day, or for my MPharm project perhaps?

Lambs can be reared by other dams in cases where the lamb is rejected, orphaned, or the dam is unable to feed the lamb itself which leads to other rearing sources. If a dam has multiple births, one of the lambs may be transferred to a dam which has lost its lamb, which allows for mutual beneficiality – the dam does not suffer the loss of a lamb and the adopted lamb gains sufficient colostrum without competition. Artificial rearing is also an option, where they are fed on milk replacers which is a powder which is usually whey based and fortified with vitamins, that is mixed with water.

There are various finishing systems (increasing muscle mass ready for slaughter) for lambs including forage only, and forage with concentrate supplementation.  The change in diet should be gradually introduced, especially if the new diet consists of high amounts of carbohydrates. This is due to the possibility of rumen acidosis. This occurs when large amounts of carbohydrates are rapidly fermented causing a reduction in rumen pH, which a favourable environment for the growth of the Lactobacillus bacteria, which produced lactic acid and further reduces pH. This Lactobacillus favourable environment is less than ideal for the survival of other microbes causing them to die. The lactic acid causes water movement into the rumen resulting in dehydration[viii].

Feed management is also related to other major health concerns of sheep – the most common being Parasitic gastro-enteritis (PGE) which is an infection of worms in the digestive system, which is a significant cause of death among lambs. To reduce infection rates, grazing management strategies are implemented, setting lambs to pasture on different fields from years to year, or rotating between sheep and cattle on the pasture[ix]. However, if an infection is detected then anthelminthics are used, of which there are five groups: 1-BZ, 2-LV, 3-ML, 4-AD, and 5-SI. Group 1 is used as both a treatment and as a control measure through drenching lambs[x]but there is also growing resistance to this category along with group 2&3 due to its widespread use. This is an oral method of liquid administration where the dose is ‘injected’ into the throat of the lamb – rather like use of syringes that come with Calpol bottles these days, only larger. Even though this is only the third blog in the agriculture series I’ve come across so many different formulations available for livestock so I’m hoping to look into these in more depth in a subsequent blog.

The average sheep produces 2kg of wool annually[xi], which is sheared by an experienced team between May and July. Most sheep breeds naturally shed their wool as the weather warms, which leads one to have a slight panic in their newly-awoken haze as they open their curtains and think ‘its snowed’ only to remember that its those effing sheep at it again. Leaving little tufts of white wool all over the fields and leaving them looking scraggly with bits of wool half hanging off their forms, looking like they’ve just been in a fight. Shearing reduces external parasitic infections and of hyperthermia in the summer. The wool is packed and sent away to be categorized into seven main groups, which arise from different breeds. These categories indicate the price the farmers gets for the fleece. I remember going to my uncle’s farm when it was shearing day and I must say, even though it looked like a high stress environment and quite physically demanding I’d quite like to try my hand at packing (not shearing, obviously, as I don’t know how and am not strong enough.  I’d end up getting kicked in the face).

Another blog down, and poorly made (its exam season after all) but its given me an opening to learn more about sheep.  Even though I try to get a little detail in, it’s difficult in the time frame and what detail I do squeeze out of publications it ends up being about diseases. Once a pharmacist, always a pharmacist.


[i]AHDB. 2019. Managing ewes for Better Returns (Sheep Manual 4).

[ii]Reed, K. 2016. Fertility of herbivores consuming phytoestrogen-containing Medicago and Trifolium species. Agriculture, 6(3)35. https://doi.org/10.3390/agriculture6030035

[iii]TEAGASC. 2017. Ewe nutrition in late pregnancy.

[iv]Armstrong,E. 2016. Research briefing the farming sector in wales. National Assembly for Wales.

[v]Simcock,E. 2019. Lambing part 4 Ensuring survival of newborn lambs. NADIS

[vi]Ahmad et al. 2000. The level of immunoglobulins in relation to neonatal lamb mortality in Pak-karakul sheep. Veterinarski Arhiv, 70(3) 129-139

[vii]Phythian et al. 2020. Mortality, morbidity, and liveweight following multivalent clostridial and pasturela vaccination of lambs on six English commercial sheep flocks. Veterinary Evidence. 5(1).

[viii]Constable,P. 2015. Grain overload in ruminants. MSD Veterinary Manual.

[ix]McCarter,P. 2019. Gastrointestinal nematode infestations in sheep. NADIS

[x]McCarter,P. 2019. Gastrointestinal nematode infestations in sheep. NADIS

[xi]British wool. British wool facts – did you know?