Sheep farmers experiencing grass shortages should consider offering supplementary feed to lambs or weaning early and prioritising better grazing for ewes to safeguard fertility, advises a leading ruminant nutritionist.

Mole Valley Farmers' nutritionist Rebecca Moore warns that ewes with a low body condition score (BCS) at weaning could see poorer ovulation, fertility and scanning rates.

And with farmers already reporting grass shortages in the south of England, eastern Scotland and temperatures set to continue, action may need to be taken soon to ensure ewe fertility isn't comprised.

She said: "Supplementary feeding of lambs pre-weaning when the grass is limited can help your lambing percentage the following year by not adding pressure on the ewe. Another option is to wean lambs early, so ewes have a longer dry period to recover. This is also the case if ewes have a low BCS."

The target should be for ewes to be one BCS up from their weaning BCS by tupping, giving them ten weeks to gain one BCS before mating if they have a low BCS.

For farmers to reach their optimal scanning percentage, number of lambs born and number of lambs weaned, 90% of ewes to be at their correct body condition score before tupping.

The target BCS’s at tupping are:

• Lowland ewe = 3.5

• Hill ewe = 2.5

• Rams = 3.5- 4 – they should be fit, not fat.

Ms Moore added: "Thin ewes should be placed on the best pasture and prioritised over finishing lambs, or receive supplementary feed to help maximise fertility in these ewes for the following year.”

"For example, if a 70kg lowland ewe needs to gain one BCS, this is around 7kg weight gain over a 100-day period. This means that ewe needs an extra 7MJ a day over the 8.4MJ required for maintenance. This equates to a total of 15.4MJ a day, or the equivalent of 1.54kg of DM of grass a day, if the grass is 10ME.

"If grass is poorer or availability is limited, supplementary feeding is required. Compound feed or feed buckets can be very useful to make up the shortfall at this time of year.

"Whilst naturally occurring soluble sugars found in the grass offers the perfect energy source, from mid-summer onwards they can be limiting, which is why supplementary feeding with good rumen degradable protein and fermentable energy sources can help," she added.

Farmers should ideally be body condition scoring their ewes every few weeks from weaning to ensure they are on track to reach their target condition at mating.

Rams should also not be forgotten as thin and poor rams can have reduced sperm quality and quantity and reduced libido and fertility, as can over-fat rams.

Ms Moore added: "Supplementary feeding of thin rams will help to improve semen quality and quantity. However, a ration should include ammonium chloride to reduce the chances of urinary stones. Rams will take around six weeks to gain a BCS."