How to maximise the benefits of grazing crops for ewes
01 July 2016
CSIRO’s Dr Cesar Pinares-Patino is contributing to an MLA-funded project examining the impact of autumn-winter and summer-autumn grazed dual-purpose wheat and canola on the performance of breeding ewes and ewe lambs, respectively.
Below are some of the results Cesar and his colleagues have observed so far:
1. All in the timing: The benefits of autumn-winter grazing are maximised when dual-purpose crops are sown early (February−March) and wheat and canola (or canola and wheat) are grazed in sequence.
2. Some supplementation required: Wheat and canola can be safely grazed by ewes in late pregnancy, during lambing and lactation. Ewes grazing wheat may need to be supplemented with a mix of sources of calcium, magnesium and sodium. However, there is no need for mineral supplementation of ewes grazing canola.
3. Introduce slowly: Sudden access by sheep to dual-purpose crops, especially canola, may potentially lead to ruminal acidosis and nitrate toxicity, meaning animals should be introduced slowly/gradually to graze these crops. Canola is characterised by low initial palatability and, in practice, sheep take more than 10 days to achieve full intakes, a period which is sufficient for the ruminal microorganisms to adapt to canola metabolites, enabling acclimatisation for healthy rumen function. Nevertheless, the low initial feed intakes may be a trigger for pregnancy toxaemia.
4. Biggest impact in poor seasons: Dual-purpose crops provide abundant, high quality feed during autumn and winter, when pasture cover is generally low. This period coincides with the high energy requirements of late pregnant and lactating ewes. In good growing seasons, performance of ewes with access to dual-purpose crops is no different from ewes with no access (i.e. on good pastures). However, during poorer growing seasons (i.e. poorer pasture availability), ewes grazed on dual-purpose crops are heavier at weaning and have heavier lambs at birth and weaning than their counterparts grazing pasture only. In both poorer and good years, systems that include dual-purpose crops have higher gross returns (+ $100−$300/ha) than pasture-only systems, resulting from the combination of less supplemental feeding (or use of on-farm stored grain for feeding) and additional income from grain.
5. Ideal for young ewes: Ewe lambs (10-months-old) can be safely joined on spring-sown dual-purpose canola, resulting in higher liveweight gains during joining and higher pregnancy scanning rates than their counterparts grazed on pasture or other alternative summer forages.
6. Merino mothers make more money: Use of dual-purpose crops during late pregnancy and lambing by Merino ewes mated to White Suffolk rams had higher gross returns from lamb production than White Dorper ewes mated to either White Suffolk or White Dorper rams. Despite the heavier weaning weights of their lambs, systems based on White Dorper ewes would need to produce 15−35% more lambs to achieve the same return per ewe as the Merino-maternal system if lambs are sold as store lambs at weaning.
Cesar Pinares Patino, E: email@example.com
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