Growing weaner sheep

Page last updated: Tuesday, 23 July 2019 - 1:16pm

Please note: This content may be out of date and is currently under review.

Looking after Merino weaners

Targets for growth in Merino weaners

There are three key management targets to ensure good weaner survival:

  • weaning weight of at least 20kg and 45% of adult weight by pasture senescence
  • growth rate of at least 1kg/month after weaning for weaners weighing 20-30kg
  • growth rate of at least 2kg/month for weaners weighing <20kg.

These targets will also aid in meeting liveweight targets for sale sheep or maiden ewes for the following mating.

Feeding lupins for better use of dry pasture during early summer

Supplementation of quality feed increases the intake and digestion of paddock feed. It is given at low levels before the paddock feed quality is lost and this is usually in the form of lupins. Typical feeding rates to maintain weaners are 25g/hd/day starting at pasture wilting (50% of clover is dead) and increasing to 50g/hd/day after 21 days. Cereal grains cannot be used as a supplement similar to lupins as the grain will always reduce or substitute the intake of dry pasture.

There is a 4-6 week 'window of opportunity' throughout the region to better utilise dry pasture for minimal cost by grazing weaned lambs on the best-feed paddocks and supplementing the sheep with 25-50g/hd/day of lupin seed.

Pasture quality and quantity below critical levels

Weaned lambs (25-45kg) are unable to consume enough feed to maintain liveweight once the feed is below a digestibility of 55% and crude protein content of 12% or the amount of dry pasture is less than 1500kg/ha. This time is referred to as the 'crunch'.

It is unknown what determines a good or poor summer feed however it may be related to the pattern of wilting (fast or slow). The quality of pasture declines with time (whether it is grazed or not) but the rate of decline differs between locations. The 'crunch' for weaned lambs generally occurs during November at Newdegate (pasture quality and quantity) and around mid–December at Mount Barker (pasture quality). It is important to monitor the condition score and weight of 50 weaned lambs in each mob of young sheep at this critical period. This identifies any increased risk of ill thrift and death occurring during late summer and autumn.

Small-scale supplementation of lupin seed (25-50g/hd/day) is not useful after the pasture quality and/or quantity are below critical levels — usually from early November at Newdegate and mid–December at Mount Barker.

Weaner condition score falls below critical levels in early summer

It is critical that all weaned lambs attain 45% of their adult liveweight and have a condition score of two or better by November. In order to monitor condition, 50 weaned lambs in each mob of young sheep should be weighed and condition scored in early November. On this basis, small Merinos (mature liveweight of 40-45kg) should not fall below 18-20kg, medium Merinos (mature liveweight of 50-55kg) below 22-24kg and large Merinos (mature liveweight of 60-65kg) below 27-29kg.

Hand feeding or rotational grazing is required (before ‘the crunch’) in order to maintain weaned lambs above 25kg and in condition score two that are grazing pastures. Cereal, canola stubbles, grazed legume stubbles or other feed sources (for example, fodder crops, lucerne, subtropical grass or saltland pastures) can be used.

An alternative approach is to supplement with lupins (at 25-50g/hd/day) for the first 42 days to improve the utilisation of dry pasture. Then increase the amount of lupins to 75g/hd/day, with a further increase to 100g/hd/day for each subsequent 30 day period. From early February onwards increase to 150g/hd/day.

Best use of cereal and canola crop stubbles

Weaned lambs should get the first choice of all crop stubble and be rotational grazed through each stubble paddock. A three week rotation is required when grazing cereal and canola stubbles as the weaned lambs would have consumed the better nutritive components (leaf) of the dry crop residues. They tend to concentrate their grazing within 800 metres of water points.

Weaned lambs are also inefficient at consuming split cereal grain on the ground. Start feeding lupins, barley or a mixture of oat and lupin within three weeks of grazing the last 'new' cereal or canola stubble paddock before weaners start losing condition.

Summer pasture deteriorates if not used

Weaned lambs should graze fodder crops, dry pastures or saltland pastures in early summer before the pasture nutritive value is less than 55% digestibility and 12% crude protein and while the amount of FOO is greater than 1500kg/ha.

Legume stubbles provide better quality sheep feed than cereal or canola stubbles. Lupinosis is the main threat on lupin stubbles within the region. Train weaners to recognise lupin seed before going onto lupin stubbles. Graze lupin stubbles as soon as they are available in early summer and use stocking rates of up to ten weaned lambs per hectare when grazing lupin stubble. Consider moving the weaned lambs when lupin seed levels fall below 100kg/ha in an 800 metre radius from the water point. Deferred grazing of lupin stubbles until late summer is a high-risk strategy.

Always ensure a plentiful supply of good quality water especially on hot days when grazing pastures and stubbles throughout the summer and autumn.

Weaner condition score falls below critical levels in late summer

Weaned lambs grazing pasture and stubbles with less than 50% digestibility and/or less than 1000kg/ha will have a higher mortality rate than adult sheep. The weaners reach this second 'crunch' point during February or March but it takes a further 3-4 weeks of restricted nutrition to deplete the fat and muscle reserves before some of the 'at risk' sheep start dying.

Any weaner with a condition score 1-1.5 are considered at extreme risk. The ‘at extreme risk' weaners for small Merinos are those below 15kg; for medium Merinos below 20kg and for large Merinos are those below 25kg. The predicted survival rate is less than 90% for all three types of Merino weaners.

The preventative action is to condition score 50 weaned lambs from each mob of young sheep during March, draft off the lightest weaners and increase the feeding rate the level of feeding to all weaners in the mob.

Ewe weaners too light to reach their breeding potential

Weaned lambs have a capacity for compensatory growth when grazing green feed after a long summer. However, it is important to reach target weights for ewes at mating. By improving the condition score from 2-3 in hogget ewes at joining it will potentially increase the percentage of lambs born.

Contact information

Danny Roberts
+61 (0)8 9892 8535