Nutritional issues in lambing ewes

By Condobolin District Vet, Dr Kirsty Cordon

Over the past three weeks in the Condobolin region, we have seen several autumn lambing ewe mobs either at the point of lambing or late gestation in negative energy balance despite an abundance of what ‘looks like’ more than enough green feed (> 2000kgDM/ha). Pastures in question are predominately summer active C4 based grass species (i.e windmill and umbrella grass), with plenty of winter active’s (barley grass, annual ryegrass and others) germinated and growing like steam.

These summer C4 species are too low in metabolizable energy (8-9 MJ ME/kg dm), which is comparable to some wheat stubbles, ewes cannot physically consume enough to meet their needs, and these paddocks are best left for maintaining dry stock. On the other hand, the young ryegrass and other winter active species have not had enough time to reach adequate density and height for these lambing ewes either.

Energy requirements (MJ/head/day) at condition score 3, Merino ewe medium frame:

DRY EWE

PREGNANT >130 days

MID-LACTATION

Single-bearing ewe

8

13

21

Twin-bearing ewe

8

16

26

Supplementary feeding is therefore critical to fill this seasonal energy deficit to keep ewes in positive energy status throughout late pregnancy and into lactation, with aims of maintaining adequate body condition for next season, producing better quality colostrum, reducing the risk of pregnancy toxaemia, and promoting more live lambs on the ground and therefore influencing overall profitability. Offering ewes an adequately balanced mineral supplement particularly when feeding cereal grain is another important consideration, it can be as simple as offering a lose lick ad lib,  50% lime and 50% salt at least 6 weeks prior to lambing to reduce the risk of hypocalcaemia and maintain adequate calcium levels during late gestation and lactation. There is also value in imprint feeding lambs onto grain while on the ewes, as lambs that have been shown how to find and eat grain by their mothers will be more likely to take to eating grain later in life.

Feed budgeting with a plan to supplementary feed is critical for producers who insist on lambing ewes in autumn. If you are seeing issues and would like assistance to calculate a supplementary ewe feeding program for your producers, we are happy to walk you through it, we can also provide feed test kits if required.

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