Limited feed puts ewes at metabolic risk

// Feed Planning and Strategies

Severe feed shortages in parts of the country mean many ewes are on a nutritional knife-edge heading into lambing and could be at risk of developing metabolic disorders.

ewe and lamb eating

Veterinarian Charlotte Westwood from PGG Wrightson Seeds, who runs the informative Facebook Group ‘The Rumen Room’, says going into set-stocking, some farmers will be considering transitioning stock from a high energy, starch-containing feed such as sheep nuts or grain onto a post-drought, lush leafy pasture-based diet.

This dietary change could put ewes, particularly multiple-bearing ewes, at risk of developing metabolic disorders such as sleepy sickness, milk fever and possibly grass tetany, particularly if there’s not enough pasture available to ewes.

While there are mineral and vitamin deficiencies associated with these metabolic disorders, Charlotte says it ultimately comes down to an absolute lack of pasture, in that ewes are simply not getting enough of all nutrients in their diet – energy, protein, vitamins and minerals.

“When they are not getting enough feed, they are not getting enough of all nutrients  – energy, protein, minerals such as calcium and magnesium – so it becomes a bit academic about whether it is sleepy sickness causing milk fever or the other way around.”

Heavily in-lamb ewes carrying multiple lambs need to have a minimum of 1400kgDM/ha of pasture underfoot at any stage to optimise their dry matter intake, a challenging requirement for many people this winter.

In regions such as Hawke’s Bay, these pasture covers are not possible this season and many farmers are having to consider continuing to feed out supplements such as sheep nuts or grain over lambing. 

“Although this is an excellent way to maintain feed intake for ewes, daily feeding out of supplements to set stocked ewes increases risk of mis-mothering between a ewe and her lambs.”

Charlotte recommends farmers take an “aircraft oxygen mask” approach. First prioritise the ewe so she is better able to look after her lambs.

“If a ewe ends up with sleepy sickness and/or milk fever, her unborn lambs are at real risk, we need to first look after the ewe then follow through with ways to protect any mis-mothered lambs”.

But feeding out supplements and keeping a close eye on wellbeing of newborn lambs could also mean more intensive shepherding over the lambing period, which in itself increases the chances of mis-mothering.

More disruption of set-stocked ewes during feed out of supplements could result in more orphan lambs this season which adds extra cost, labour and stress after what has already been a very long year.

Farmers could consider setting up hand-rearing facilitates in preparation for mis mothered lambs and consider asking for help from friends and family with hand rearing lambs over the lambing period.

Charlotte acknowledges there is no easy answer this season, but strongly recommends that going into lambing, farmers update their feed budget – irrespective of how little feed they have – and work alongside their vet or consultant to make a plan about which ewes to prioritise based on scanning results, other stock classes on the property, average pasture covers and supplementary feeds available.

For example, it might be worthwhile feeding supplementary feeds to the single-bearing ewes to allow pasture covers to build on other parts of the farm so that twin and triplet ewes can be set stocked and left uninterrupted to lamb onto appropriate amounts of pasture. Mis-mothering may be less risky for ewes with one lamb at foot than those with triplets. Alternatively, make well-conditioned single-bearing ewes a lesser priority and focus feed and resources on the multiple-lambing ewes.

“But this should be evaluated on a case-by-case basis – there is no one-size-fits-all recommendation for everyone.  For example, in some situations, ewes might need extra minerals, such as magnesium if pasture at set stocking is very short and leafy”. She encourages farmers to talk to their vets about what might be required.

Charlotte sums up by saying there is a real tension between fully feeding the ewe with supplementary feeds pre-lamb and increasing the chances of mis-mothering and potential lamb losses, but that heavily pregnant stock – cows and ewes - should be the priority so adequate maternal body condition, colostrum and milk yield gets the lambs and calves through.

“This is not the year to be set-stocking at risk heavily pregnant stock on 800kgDM/ha pasture, shutting the gate and hoping they’ll do OK.”

Lambing with limited feed resources adds another layer of pressure on already-stretched farmers. B+LNZ have been working alongside the Ministry for Primary Industries and other organisations to provide feed planning, feed coordination and support services to farmers.

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