By Fiona Lovatt, sheep veterinary consultant

Body Condition Scoring (BCS) is well established as a key tool for monitoring pregnant ewes, and ensuring they meet the needs of a farm’s production cycle.

Despite this, the harm caused by a fall in BCS is more threatening than it first seems – potentially impacting ewe fertility and limiting the development of healthy lambs.

“We definitely have solid evidence to show ewes in poor body condition have their ovulation rates affected significantly,” says Fiona Lovatt, independent sheep veterinary consultant.

“More and more progressive farms are realising just how key BCS is to their productivity. Blowfly strike is just one of the underestimated ways in which BCS can take a hit – it’s important to not get caught out at the end of the season and ensure ewes are ready for tupping.”

Nutrition in numbers

Most farms will be aware that post weaning they will need to regain the flocks condition lost through lactation but many might not see the additional impact preventatable issues such as blowfly strike can have too. Poor BCS doesn’t just indicate a ewe has fallen below its potential, a ewe with low BCS going into pregnancy will struggle to meet her own nutritional energy requirements, let alone the requirements to support two lambs.

Energy required to lift a ewe by one body condition score

Maintenance requirements = 8.4MJ of metabolisable energy

Improvement requirements = 7MJ of metabolisable energy (assuming 100-day weaning-mating window)

Total = 15.MJ per day per ewe

Nutrition Required

Concentrate strength = typically 12.5MJ ME/kgDM

Total requirement to restore lost BCS = 56kg DM (65kg as fed, the equivalent of 2.5 bags of feed per ewe).

Fiona pointed out the long-term disadvantages caused by low BCS: “It’s virtually impossible for the ewe to eat enough to support two lambs and herself. She’s always going to lose a bit right at the end of pregnancy and a poor BCS at the start will pose a real disadvantage. This doesn’t just affect that specific lambing season; the resulting colostrum is less good; the milk is less good… the effects therefore extend into the following year’s round.”

Early effects

Follicles begin developing in a ewe’s ovaries six months before ovulation. A ewe going to the ram in September will therefore be preparing for ovulation straight from lambing time. Optimal body condition is essential during this period; a ewe’s physiology is dedicated to priming the ovaries for conception, and poor health will directly compromise fertility rates and the number of lambs produced.

Ensuring the ewe remains healthy over the summer is absolutely crucial to ensure a strong scanning percentage.

“Ewes are much less likely to have twins or triplets, even if pregnancy itself continues, due to lower ovulation rates. Oestrus behaviour is also compromised, with many not achieving oestrus correctly.”

For ideal productivity, a ewe needs to be in the best condition possible from tupping onwards. Any losses in BCS – even from an early stage – will affect the beginnings of ovulation. The knock-on effects will result in elevated stress levels, fewer doubles, and substandard nutrients for healthy lambs.

Minor afflictions, major effects

Even a body condition loss of one score has an effect; the more severe the drop, the longer a ewe will take to recover, and the greater the productivity loss. With this in mind, it’s important to prevent any adverse conditions that can jeopardise BCS.

Even minor cases of afflictions like blowfly strike can have serious consequences to a farm’s profitability. When a ewe is struck but successfully treated, the resulting costs go beyond those of immediate treatment.

Variable weather patterns have led to a less predictable blowfly season this year, and Fiona also said many farmers are still getting caught out each year.

“I don’t think it’s at all ridiculous to say that a ewe recovering from fly strike this year will have an effect on next year’s lambs, even a mild case of strike will still result in lost weight after the crisis stage,” added Fiona Lovatt. “With the variability in weather from year to year, we are at the mercy of the weather, so it’s best to apply a treatment that gives you the best coverage.”

Optimum BCS is vital for a productive farm. A ewe with lower BCS, even if caused by a seemingly minor incident like “light strike”, is less likely to get in lamb and suffer from lower conception rates, right from the point they go through to the tup. Substandard BCS puts ewes at a disadvantage even months before lambing – and the consequent loss in fertility has a drastic impact on farm productivity well into the next year.

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