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Careful ewe feeding the key to successful lamb production

Warm weather and excellent grass growth in large parts of the UK this autumn means that many ewes will have gone to the ram in good condition. This should help lift lambing percentages, but will also have increased the likelihood of ewes entering late pregnancy too fat.

Unless feeding is carefully managed, this could increase the risk of pregnancy toxaemia, commonly known as twin lamb disease, which can result in weak, low birthweight lambs, poor survival rates and even ewe death. What’s needed is a carefully managed transition through late pregnancy and into lactation to optimise lamb birthweight, lamb vigour and ewe milk production.

Achieving the correct body condition score (BCS) of 2.5-3.0 in late pregnancy is also critical, and research has shown that slight under-nourishment of ewes tupped in good condition during mid-pregnancy can actually help stimulate placental growth and encourage strong lamb development. With a drop in body condition of up to 0.5 BCS acceptable, nutrient demand during this period can usually be met by good forage plus minimal supplementation.

Figure 1 – Foetus development during ewe pregnancy

But to maintain this condition through late pregnancy some extra feed will be needed. Lamb survival and the ewe’s mothering ability (including milk production) are greatly affected by ewe nutrition during the last third of pregnancy as about 70% of the foetal growth will take place during the final 50 days (Figure 1), along with development of udder tissue.

The traditional approach is to offer incremental increases in the amount of concentrates as lambing approaches, known as step-rate feeding. An alternative is to offer the same amount of concentrates as a flat rate throughout late pregnancy, reducing the need to feed large quantities as lambing approaches, as well as to simplify feeding overall (see Table 1).

Table 1 – Example concentrate feeding regimes for a twin bearing ewe fed ad libitum straw*

* Quantities recommended should be split into meals to avoid feeding more than 0.5kg/head at any one time.

Aim for an energy content of at least 12.5MJ ME/kg DM, plus 1618% crude protein if feeding hay or silage, or 20% for straw-based rations. The level of feeding can then be varied around those figures in Table 1 to match the different needs of each group in the flock – slightly less for ewes that are over-fit, slightly more for thin ewes and ewe lambs still growing.

Feed costs can also have a big impact on overall profitability. Although pelleted compounds are more convenient, they’re also more expensive than straights or blends and give much less flexibility (Table 2).

Table 2 - Example rations for late pregnancy ewes         

¹ Bio-ethanol co-product wheat distillers’ pellets have low copper.

² Price estimates correct at time of going to print based on bulk loads delivered to the Midlands, and will vary on farm location and load size.

Just don’t be tempted to feed large amounts of home-grown cereals – too much starch can very quickly upset the rumen and cause acidosis, leading to lower birthweights and poorer milk quality. Using cereals as part of the ration is not a problem, but make sure the starch is buffered adequately in the rumen by also feeding sources of digestible fibre like sugar beet feed and/or Scottish barley distillers’ feed, as shown in Option 4 in the table.

Once the ewe has lambed and is lactating, she still requires large quantities of supplementary feed, and it’s not unusual for a large early-lambing ewe with twins to need 1.5kg/head/day of concentrate during lactation, for example. The simplest and easiest solution is to continue feeding the same supplement used in late pregnancy, at least for the first four weeks of lactation – the lamb is entirely dependent on milk for all its nutrients during this time, so supplements with the same high energy and protein levels as recommended for late pregnancy are ideal.

Digestible fibre in the ration has also been shown to be extremely important in promoting milk fat production. Research work conducted at Writtle Agricultural College, for example, demonstrated that feeding sugar beet feed as part of a lactating ewe’s ration consistently improved milk butterfat levels, and hence the energy content of the milk. Repeated on farm, the result would be higher lamb growth rates, greater weaning weights and quicker finishing.

Similar work completed at ADAS Rosemaund concluded that simple 50:50 mixes of sugar beet feed and low-copper barley distillers’ pellets - plus a suitable vitamin and mineral supplement - could successfully replace a barley-plus-soyabean-meal type concentrate for lactating ewes at grass. In addition to the potential benefits in terms of ewe milk production and lamb growth, it’s an option which could become increasingly important where the traceability and GM status of feeds have to be assured.

Table 3 – Diets used in ADAS trials ¹       

¹ Both diets supplemented with appropriate vitamins and minerals.

² Advice should be sought before feeding Scottish distillers’ feeds to ewes due to the copper content.

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