Nutrition and health of ewes after the break

Ewes due to lamb in autumn and winter will often not be able to get all their feed requirements from the pasture. In autumn, the feed is usually short and dry, and lacking in energy and protein.

After the break, protein is unlikely to be limiting, but it may take some time for the pasture to reach adequate density and height for lambing ewes. The amount of dense green perennial pasture required for lambing ewes to maintain weight is:

• 900kg DM/ha FOO (feed on offer) by day 90 of pregnancy (about 2.5cm of dense green pasture)
• 1200kg DM/ha FOO at lambing for single-lambing ewes (about 4cm of dense green pasture)
• 1800kg DM/ha for twin-lambing ewes (about 7.5cm of dense green pasture).

Targets for good quality annual pastures will be less.

Ewe condition

Ewe condition in late pregnancy affects lamb birthweight and survival. Most of the growth of the developing lamb occurs in the last 50 days (7 weeks) before birth, so good nutrition in late pregnancy ensures that optimal lamb birth weights and lambing targets can be achieved. It also lowers the risk of pregnancy toxaemia, to which twin-bearers are particularly susceptible.

The recommended condition score (CS) targets developed by Lifetimewool suggest that, from joining to lambing, both single-bearing ewes and twin-bearing ewes should maintain a CS of 2.7+.

To maintain condition, a late-pregnant ewe must have higher amounts of feed available. Their requirements increase by 80 per cent for twin-bearers and 50 per cent for single bearers by lambing, then increase even further after lambing (Table 1 and 2).

Table 1. Energy requirement (MJ/head/day) at condition score 3 of a single-bearing ewe

Table 2. Energy requirement (MJ/head/day) at condition score 3 of a twin-bearing ewe

Ewes that are thinner (for example, CS 2) will have slightly lower energy requirements for maintenance, as will ewes that are fed in containment areas. Such ewes are at higher risk of mortality during lambing, so efforts should be made to improve their nutrition and condition.

Lamb survival

Twin lambs are particularly sensitive to changes in ewe CS. With lower birth rates expected compared with a single lamb, good ewe nutrition is especially important. A higher ewe CS at lambing (CS 4 rather than 3) can increase lamb survival by 10 per cent in a twin-bearer. On-farm trials in Victoria found that 15 to 20 per cent more lambs survive when born to ewes of CS 3.0 to 3.5 than to ewes at CS 2.0 to 2.5. Ewe mortality can be significant when CS is 2 or less.

Figure 2 illustrates the importance of good ewe condition.

Ewes in better condition rear more lambs … because more lambs are born with the optimum birthweight … and less ewe mortality occurs in late pregnancy if ewes are better conditioned

(Source: Lifetimewool)

Assess ewe condition around scanning time and pre-lambing

Single-bearing and twin-bearing ewes can be managed to their specific feed requirements by pregnancy scanning at day 90 from the start of joining, and using the results to separate the ewes into dry, single and twinning flocks. This is particularly useful when feed supplies are low or supplementary feeding is expensive because it ensures the most efficient allocation of feed resources over late pregnancy. Any individuals below CS 2 should be managed separately and have increased access to good feed before lambing, especially any twin-bearing ewes.

It is important to ensure that both energy and protein levels are adequate during late pregnancy if ewes are still on dry feed. If the break has come and pasture growth rates are high, energy intake needs to be high enough to maintain ewe condition. Green pick will increase the available protein.

If using grain and supplements for your ewes, and the break is late, consider saving any good-quality roughage (good hay or silage) that can be fed quickly and safely in wet or cold weather.

When lambing in autumn or winter, pasture targets are difficult to achieve. Having ewes in better condition during autumn helps to buffer some of the inevitable weight loss.

Monitor health

With the autumn break come a few potential animal health issues. The most common is internal parasites — with moisture, worm eggs will hatch and develop into infective larvae. Hopefully, you have completed appropriate control over the summer period. However, in some areas, heavy summer rains may have made good summer worm control more difficult.

The most vulnerable animals are weaners and pre-lambing ewes. The weaners will require worm egg count monitoring 4 to 6 weeks after the break and throughout winter. If the weaners are under high-risk conditions, monitoring will need to be more frequent. Pre-lambing ewes also need to be monitored, especially if they are in low body condition and grazing short pastures. Ewes should be monitored 6 to 8 weeks after the break.

The worm Nematodirus is rarely of importance on its own, but after a dry summer it can be of special note. Mass hatchings may occur after the break, and intake of larvae is high if sheep are grazing short green pick. Signs include scouring, ill-thrift and weaner deaths. A great source of information on worm management is WormBoss.

Calcium deficiency (hypocalcaemia) can be an issue after the break if pregnant ewes or weaners are grazing lush green feed. Hypocalcaemia can also occur when sheep are taken off feed, such as for yarding or travel. Sheep experiencing hypocalcaemia will show nervous signs such as staggering and lethargy, and may even go down. Treatment with a flow pack ('4-in-1' or straight calcium) usually results in recovery. However, it may be worth talking to your local vet before treating. Prevention includes offering a source of roughage such as hay or straw, or providing calcium (such as limestone) supplementation if the sheep are on a grain diet. Most issues with hypocalcaemia can be prevented by providing good nutrition and husbandry.

With moisture after the break, feet also become important, so monitor for conditions such as footrot and ovine interdigital dermatitis ('scald'). The signs include lameness, reddening between the toes, a white scum on the skin surface, or even separation and underrunning of the horn of the feet.

Early diagnosis and treatment is vital for effective management, and any lame sheep should have their feet checked as soon as they are noticed. Lame ewes are unable to forage well enough, which can predispose them to pregnancy toxaemia.

In summary, remember the following:

• If it is likely that ewes will not have access to enough quality pasture, consider maintaining condition throughout pregnancy and allocating feed (paddock and supplements) to ewes with different needs (for example, fat versus skinny, single versus twin lambers).
• The CS of the ewe during late pregnancy influences the birthweight and survival of the lamb(s).
• Ewes in better condition lose fewer lambs.
• With the break come worms — monitor 6 to 8 weeks post-break.
• Calcium deficiency and foot problems can be an issue after the break.
• If feeding high rates of supplements to ewes, and the break is late, consider saving any good-quality roughage that can be fed quickly and safely in cold and wet conditions.

The recommendations for CS and pasture availability in this article have been developed by Lifetimewool to optimise ewe and lamb survival.

Erica Schelfhorst, Livestock Extension Officer, and Rachael Holmes, District Veterinary Officer, Bendigo