The way ewes are fed in mid-pregnancy can have a significant knock-on effect on subsequent lambing performance.

This was one of a number of nutritional tips delivered by Teagasc sheep specialist Frank Hynes to a large crowd attending last week’s Teagasc Winter Sheep Seminar in Athenry, Galway.

Frank explained that to promote successful embryo implantation to the wall of the uterus, ewes require a high plane of nutrition for at least 21 days post-conception.

As a general guide, he said that a high plane of nutrition should be continued for a seven-week period post ram turnout.

This will ensure that adequate time is given for the majority of ewes to be mated as well as accounting for a normal repeat rate within the flock.

Once pregnancy is established, feeding levels should be based on ewe condition. Research has shown that a small level of weight loss in mid-pregnancy is beneficial for good placental development. But the degree of weight loss is very much dependent on ewe condition.

Frank cautioned that severe underfeeding in mid-pregnancy should be avoided as it will lead to very poor placental development, reduced lamb birth weight and can also have subsequent negative effects on lamb performance.

There are three main scenarios and feeding regimes to consider as listed below.

1) Ewes in poor body condition (BCS 2.5-3)

For ewes in poor condition mid-pregnancy, feeding levels should be targeted to improve body condition. This will have the positive effect of also promoting good placental development.

Ewes in this category should be given preferential treatment with the target of improving body condition before ewes enter late pregnancy.

It will be very difficult in late pregnancy to improve body condition while also meeting increased nutritional demands of foetal growth.

2) Ewes in very good condition (BCS 4 plus)

Frank explained that the strong grass growth this back end has resulted in a high percentage of ewes gaining significant condition during flushing and mating.

These ewes, in many cases, can afford to lose half a body condition score or approximately 4kg to 5kg liveweight in the weeks ahead.

Weight loss should be gradual over a period of time. For example, ewes can be used to graze out or clean off paddocks before closing or supplemented with average to good quality silage (65 to 70DMD).

Where ewes are in very good condition and continue to be offered top quality grass, it will have a negative effect on placental development which in turn will reduce lamb birth weight.

This is as the ewe’s system is accustomed to using the extra nutrient intake for weight gain and will continue to defer nutrients to weight gain as opposed to placental development.

Additionally, ewes in excessive condition at lambing are also prone to increased lambing difficulties due to a build up of abdominal fat around the birth canal.

3) Ewes in recommended body condition (BCS 3.5-3.75)

For ewes in adequate body condition or slightly above good body condition, the advice is to feed to maintenance or slightly below maintenance levels.

Ewes can be allowed to lose up to 5% of body weight but should not be allowed to lose excessive weight that would see them fall under a target body condition score of 3 entering late pregnancy.

This is the preferred condition and is the reasoning behind the advice.

“Feed the ewes well for six to seven weeks, then if ewes are in good condition, you can afford to lose a bit of weight and while doing so provide ideal conditions for placental development,” Frank said.

Access to reasonable quality grass or ad-lib good quality silage in excess of 72DMD will be sufficient to maintain ewe condition in mid-pregnancy.

Frank said the mistake is often made of doing everything right for breeding and then forgetting about ewes until it comes to feeding in the run-up to lambing.

He advised farmers to use the grass they have left wisely and to target it to the ewes that are in most need of it.

Body condition should be monitored on an ongoing basis and remedial action taken as necessary.

There was also a word of caution to flockowners not to re-graze areas that had been closed, and now developed a cover of grass, or continue to graze all areas of the farm.

To have a sufficient supply of grass post-lambing, swards require a rest period of about 120 days. The recommended area to close to have a sufficient supply of grass next spring for mid-season lambing flocks is one acre for every five ewes.

Be careful of silage quality

Farmers were also told to be cautious and not to overestimate their silage quality. A dry ewe in mid-pregnancy requires approximately 0.8UFL energy intake per day for maintenance alone (1kg of barley provides 1UFL). 1kg silage dry matter (equivalent to 5kg silage freshweight at 20% dry matter) at 72/73 DMD is sufficient to meet this demand.

Frank told farmers that while silage may be good quality compared to last year, it may not actually be as good as you think. Overestimating silage quality can result in excessive weight loss.

Table 1 shows the energy levels in UFL per kg dry matter at varying silage and hay DMD. If silage is the main feed in mid-pregnancy and provided it is good quality (>70%DMD) with a good protein content of 11% to 12% crude protein, no supplementation apart from minerals/vitamins is necessary.

As can be seen in Table 1, as the DMD of silage/hay reduces, ewes will need to consume higher volumes to meet their daily nutritional demand.

However, where the DMD of silage is around or under 60 DMD, and also where silage is very wet, it will be hard for ewes to physically consume greater than 0.6kg to 0.7kg dry matter of silage.

Where the feeding value is poor, ewes may at best only consume about 50% to 60% of their daily nutritional requirements and can lose as much as 1kg liveweight per week.

Where this occurs, silage will need to be supplemented with concentrates, feed buckets or an alternative feed such as molasses or beet.

The advice for farmers is to get your silage tested or to err on the side of caution when estimating feeding value of forages. Ewes should also be monitored frequently to ensure that body condition is not reducing excessively in mid-pregnancy.