Sheep producers are often heard complaining about ewes that produce thick and sticky, slow-flowing colostrum, with a subsequent negative effect on lambs. Several studies indicate that this problem can be directly attributed to poor ewe nutrition during late gestation.
In an article titled ‘Colostrum production in ewes: A review of regulation mechanisms and of energy supply’ by Banchero et al., published in Animal in 2015, the authors point out that lamb losses in extensive production systems can largely be attributed to colostrum availability. Colostrum production, in turn, is directly dependent on ewe nutrition in the last weeks prior to lambing.
The energy requirements of ewes expecting multiplets are significantly higher than those carrying single lambs. The problem is exacerbated by the fact that these ewes simply do not have enough space in their rumen to ingest sufficient roughage to meet their energy requirements.
Grazing alone is therefore insufficient in meeting these ewes’ requirements and an energy supplement in the last week of gestation is essential. The extra energy ensures better colostrum production and makes the colostrum more fluid, thus promoting ingestion.
Nutrition for colostrum production
According to the authors, the majority of energy-rich grains tend to increase colostrum production by between 90 and 185%. They concluded that short-term supplementation of energy-rich grains is therefore a cost-effective way of managing ewes under extensive grazing conditions and subsequently boosting lamb production.
The fact that approximately 80% of lamb mortalities are linked to ewe nutrition during the last few weeks prior to and immediately after lambing, further emphasises the importance of adequate, correct nutrition during late gestation.
They caution, though, that adequate protein intake is just as vital, seeing as over- or underfeeding protein can affect the amount of colostrum produced at birth.
Nutrition during late gestation
According to the late Dr Jasper Coetzee, late gestation (months four and five) is one of the most critical stages in the ewe’s reproductive cycle, as approximately 80% of foetal growth occurs during this stage. This, in turn, leads to a sharp increase in the nutritional requirements of the ewe during late gestation.
The fact that approximately 80% of lamb mortalities and a decrease in lamb production is linked to ewe nutrition during the last few weeks prior to and immediately after lambing, further emphasises the importance of adequate, correct nutrition during late gestation. If ewes are underfed for even one week during late gestation, he warned, no good nutrition provided later on will be able to undo the damage.
Ewes in late pregnancy carrying single foetuses must ingest adequate nutrients (bypass protein, energy, minerals, trace elements and vitamins) from four weeks prior to lambing, those carrying twins from six weeks prior and those carrying triplets from eight weeks prior to lambing. This will stimulate udder development, increase colostrum and milk production, improve the maternal traits in ewes and lamb vitality, limit birth difficulties (yellow lambs at birth) and abnormally thick, sticky colostrum, and ensure an ideal birthweight (3,5 to 5,5kg).
These factors all contribute to maximum lamb survival, which helps producers to reduce lamb mortalities and/or increase lamb production.
Value of bypass protein
In his work, Dr Coetzee emphasised the fact that udder development is directly dependent on the amount of bypass protein ingested. By supplementing bypass protein on poor-quality dry grazing, the weight of lamb weaned per ewe can be increased by as much as 5,1kg and the subsequent lambing percentage by up to 28 percentage points.
In order to ensure a good birthweight (3,5 to 5,5kg) for a high lamb survival rate, mature ewes should exhibit at least a 15% (i.e. 7,5kg for a 50kg ewe) and young ewes a 10% weight increase during the last two months of gestation.
Providing a high-bypass protein lick with sufficient energy at 300 to 500g/ewe/day prior to lambing is non-negotiable. If grazing is limited or in instances where ewes lamb in lambing camps or pens, a complete ration must be fed from four or even six weeks prior to lambing. If the ration contains urea, intake should be limited to 2,5kg/ewe/day to prevent urea poisoning.
Ewes should be gradually adapted to the complete ration in a bid to prevent acidosis. Malnourished ewes in late gestation exhibit a lower peak and sustainable milk production than well-fed ewes. Ewes should also be given a Multimin™ (G1853) and vitamins A and E injection four to six weeks prior to lambing, as well as the necessary dosages and multi-clostridial vaccinations.
Nutrition during lactation
According to Dr Coetzee, the nutritional level during the first two months after lambing should limit ewes’ weight loss to no more than 10%. Trials show that ewes that lost more weight had a subsequent lambing percentage of 25 – in one case it was 51 percentage points lower.
Ewes may lose condition during early lactation, as long as their condition score remains above 2, but preferably not lower than 2,5. The objective is to limit weigh loss in young ewes that are destined to lamb for the first time, to no more than 3% and mature ewes to no more than 7% during the first two months of lactation. When feed intake is restricted, milk production can be reduced by up to 50%.
The growth of twin lambs is adversely affected if the diet of lactating ewes is restricted for more than ten days. A four-week nutritional restriction will impair the milk production of lactating ewes with no increase in milk production, even if ad lib nutrition is provided. Ewes should ideally be moved to cultivated green pastures or grazing maize after lambing.
To ensure a high weaning weight as well as a high lambing percentage and overall lamb production, the same bypass protein-based lick or complete ration fed during late gestation should be given during early lactation while ewes are on the available grazing. Once lambing has concluded, the late gestation nutritional levels of the protein lick must be increased by approximately 100g/ewe/day, while a full ration for ewes nursing single and twin lambs must be fed at around 3 and 4%, respectively, of their bodyweight.
Nutrition during lambing
Adequate ewe nutrition, especially bypass protein, during late gestation is essential to ensure the following:
- Optimal birthweight of 4,5 to 5,9kg. If it is less than 4kg, the risk of lamb mortality increases drastically. Birthweight is key to lamb survival. The Lifetime Wool project in Australia shows that around 70% of the likelihood of a lamb surviving is determined by its birthweight.
- Maximum udder development and colostrum production. Udder development is directly dependent on the intake of bypass protein.
- Production of good flowing colostrum. Abnormally thick, sticky colostrum is associated with low colostrum production, is difficult to suckle from the teat and delays the onset of lactation. Newborn lambs must start suckling within the first hour after birth. The longer it takes for suckling to commence, the greater the risk of the lamb succumbing.
- Limiting metabolic diseases such as ketosis and milk fever. Symptoms of subclinical milk fever include when more than 3% of ewes need assistance while giving birth because of stuck lambs, even though their birthweight is below 6kg; a high percentage of yellow lambs; more than 1% vaginal prolapse; ewes that are only partially dilated or not dilated at all; and ewes that lie down for long periods shortly before and after birth. Ewes with subclinical milk fever will have a suppressed appetite or will stop feeding altogether, which will lead to ketosis.
- The number of follicles a ewe lamb will have in her lifetime are deposited in the ovaries 50 days prior to birth. The nutrition of ewes in late gestation are therefore essential in promoting the lifetime reproduction rate of their ewe lambs. The ewe lambs of ewes that were at a high nutritional level during late gestation, have a 14% higher lambing percentage at first lambing than young ewes whose mothers were at a low nutritional level during late gestation. – Izak Hofmeyr, Stockfarm
For references, send an email to Izak Hofmeyr at firstname.lastname@example.org.