A few key principles that affect the lifetime performance of replacement ewes are reviewed in this article. The number of replacement ewes in a sheep farming enterprise normally ranges between 25–30% of the breeding ewes. Direct rearing costs of replacement ewes, such as veterinary costs and nutrition, are well recorded, but quite often the indirect costs associated with maiden ewes, e.g. age of first lambing, mortality rate, and the cost of less breeding ewes because maiden ewes take up space and utilise limited resources are overlooked or at least not properly calculated.
Managing weight versus weaning age
Standard practice is to wean when lambs are between 100 and 120 days old. The lactation curve of suckling ewes peaks at between three and four weeks after lambing and gradually decreases from peak production to reach approximately 20–30% of their peak milk production at 120 days into lactation. The environment, nutritional status, health status, and whether the ewe is suckling singles or twins can impact the lactation curve. At this time, the milk represents around 10–20% of the lamb’s nutrient intake.
Also, keep in mind that young animals are more efficient in converting feed into live weight. It makes sense to invest operating capital in the young lambs at this stage and to utilise the favourable feed conversion ratio instead of feeding late-lactation ewes that will partition much of the expensive nutrients into More than just feed body condition instead of milk production. A high-quality, palatable creep feed is very useful in this period and can significantly reduce weaning stress and limit weaner mortalities.
When the weaners have settled and recovered from the weaning stress, the creep feed can be replaced by a specialised production lick that is focused to improve protein deposition and frame growth.
A strong correlation exists between pre-weaning growth rates and weaner survival rates. Higher growth rates in the pre-weaning phase materialise in heavier weaners with lower mortalities in the stressful early weaning period. Stronger and healthier weaners also have higher post-weaning growth rates. Data from Australia indicates that a 2kg heavier weaning rate reduced the mortality risk shortly after weaning by 22%. Higher growth rates after weaning further supported survival rates and also ensured that maiden ewes achieved breeding weight targets at a younger age, reducing the number of replacement ewes required.
Limiting the suckling period allows for an extended rest period and more time for the breeding ewes to recover body condition before the next breeding season. This should result in higher conception rates, more multiples, and stronger lambs at birth with lower early lamb mortality. Mature ewes recover condition reasonably quickly and a longer rest period will decrease the need for supplementary feeding during this period.
• Move weaner lambs onto high-quality pastures and ensure sufficient grazing is available.
• Ensure easy access to cool and clean drinking water.
• Implement a proper health programme to ensure weaners are free from internal and external parasites.
• Drive higher growth rates both pre- and post-weaning to utilise the favourable feed conversion ratio of the young animal.
• Achieving breeding weight targets for maiden ewes at a younger age reduces the carry time of replacement ewes and makes more resources available for breeding ewes that generate the income for the operation.
• Heavier maiden ewes achieve higher conception rates and more multiples.
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