Deferred grazing for winter lambing ewes

The practice of autumn pasture saving involves deferring grazing after the autumn break until feed on offer (FOO) is sufficient to sustain the growth of enough feed through the winter until spring, when pasture growth increases dramatically.

Creating a feed wedge after the autumn break requires increased levels of supplementary feeding while stock are kept either in containment or in sacrifice paddocks. This can come at significant expense, depending on the level of supplementation required and fodder costs.

The Glenthompson–Dunkeld BestWool/BestLamb group embarked on a three-year Enhanced Producer Demonstration Site project between 2016 and 2018 with Agriculture Victoria (co-funded by Meat & Livestock Australia), to help weigh up the costs and benefits of autumn saving.

The demonstration

Each year, the demonstration was hosted by a different producer from the group. Composites were used in the first and second year, and merinos in the third year. Each mob lambed in early July.

Immediately post-scanning (April), a mob of twin-bearing ewes was randomly and equally split into:

• a deferred mob (implementing autumn savings)
• a set stocked mob.

Both were allocated a portion of the farm with similar area, terrain, soils, pasture species and soil fertility.

The deferred mob was kept in containment and fed a grain and hay ration meeting their energy, protein and fibre requirements until FOO was adequate to meet the target for twin-bearing ewes at lambing (approximately 1400kg DM/ha). At that point, the ewes were released into paddocks and were set stocked over lambing.

The set stocked mob was grazed according to the producer’s usual management style and was split across the treatment paddocks just before lambing.

FOO and feed quality were measured monthly, and ewe condition was measured at regular intervals.

The demonstration measured and compared lambing percentage, lamb weight and ewe condition score, and calculated profit margins for the two treatments each year.

Feeding in containment

The deferred mob spent an average of 33 days (range 28 – 40 days) in containment to enable adequate FOO accumulation to meet the target of 1400kg DM/ha for lambing. The cost of feeding sheep in containment averaged $5.17 per ewe over the three years. Because of the early and good autumn break in 2017, the FOO at lambing exceeded the target.

This was also the case in 2018 when the producer applied a mid-June application of urea, dramatically increasing pasture growth. As a result, the ewes could have been released from containment earlier, which would have reduced the cost of feeding and improved overall profitability.

Feeding ewes in containment after the break was a challenge because of muddy conditions, and feeding on the ground led to high wastage.

Extra pasture

The extra pasture grown before lambing in the deferred grazing groups averaged 850kg DM/ha, equating to an extra 27.7t DM each year over the deferred paddocks. This was consistent at each property.

The larger leaf area in the deferred paddocks led to rapid pasture growth, which continued at a higher rate when sheep were released (Figure 2). The largest difference in FOO between the groups occurred in early lambing. The extra pasture cost $48/t, calculated using the costs of feeding ewes in containment.

The value of this pasture compares favourably with using urea to grow extra grass, which was estimated to cost $100/t DM – that is, around twice the cost of containment feeding. FOO levels in the deferred paddocks exceeded the 1400kg DM/ha target in year 2 and by even more in year 3. A reduction in crude protein was measured where pasture became rank.

This may have affected lamb growth rates in 2018, which were lower in the deferred mob.

Livestock production

Ewes lost condition in containment each year while, at the same time, the set stocked mob was gaining condition in the paddock. This was reversed when the deferred mob was released from containment: they rapidly gained condition while the set stocked ewes lost condition.

This contributed to heavier lamb weights in the deferred mob in years 1 and 2. Fluctuations in condition score between the deferred and set stocked mobs were less pronounced in year 3, when merino ewes were used.

Animal performance varied considerably over the 3 years. It was negatively affected by management issues such as low condition score before entering containment, problems with transition into containment and feeding contained sheep in wet conditions.

Across the three years, in the deferred mob compared with the set stocked mob:

• lambing percentage ranged from +7% to –14%
• lamb weight in September ranged from 2.1kg heavier to 1.8kg lighter
• lamb production per ewe ranged from +5.5kg to –4kg per ewe.

Profit margin

Profit varied according to feed costs, lamb prices and animal performance each year. The difference in income between the treatments ranged from $8.99 per ewe higher in the deferred mob (year 1) to $18.54 higher in the set stocked mob (year 3).

The value of containment can be seen in the ability to run extra stock through winter, which allows increased utilisation of feed through spring. Containment feeding led to accumulation of an additional 850kg DM/ha of pasture FOO, on average.

Overall, the demonstration showed that autumn saving can be a cost-effective method of growing additional pasture for lambing ewes in winter.

However, management needs to be flexible and cater for the season – for example, some good autumns may require little or no deferment. Management and monitoring of ewes close to lambing is also a challenge in containment, particularly when the break occurs.

Tips and observations for autumn saving and containment feeding

• Appropriate feed transitioning is essential – both into containment and from containment onto green pastures – particularly near the point of lambing.

• Feeding in containment and preventing condition score loss in ewes can be challenging after the autumn break. Ensuring that they consume the full ration is difficult in a muddy environment.

• Feeding on the ground in wet conditions will lead to poor utilisation and adversely affect livestock. One producer estimated 60% wastage during containment feeding on the ground after the autumn break.

• To accurately predict FOO at lambing, feed budgeting and regular pasture monitoring are essential. If ewes enter the paddock too early, target FOO will not be achieved. If deferment is too long, containment costs will be higher than necessary, and pastures may be underutilised, causing wastage and subsequent reductions in quality.

• It is important to have all ewes in appropriate condition score (>3.0) before they are contained, because ewes lost condition in containment in each year of the demonstration.

• When set up well, feeding in containment can help to ensure that animal nutritional requirements are met.