Thursday, 18 November 2021 13:55

Are terminal sires being utilised enough?

Written by  Paul Kenyon
Massey University’s Professor Paul Kenyon says it is surprising that more terminal sires are not utilised on NZ farms. Massey University’s Professor Paul Kenyon says it is surprising that more terminal sires are not utilised on NZ farms.

Terminal sires can be a great tool to increase lamb growth rates.

They allow for either earlier target slaughter weights being achieved at the same calendar date, or heavier carcase weights. Terminal sires can also potentially reduce the risk of over fats at higher carcase weights.

Achieving earlier targe slaughter weights can have the advantage of achieving higher per kg carcase values before the price begins to decrease, when many lambs come onto the market. Another often overlooked potential advantage is the feed saved, which can then be targeted for other classes of livestock, including replacement ewe lambs. Further, the earlier a lamb is sold the less it is exposed to potential animal health issues over the summer period and less labour is required.

Recent bio-economic modelling by the Agri-business group at Massey University showed the combined effect was a significant increase in per ha sheep farm enterprise cash operating surplus. The size of the surplus was greater as lambing percentage increased allowing for more ewes to be bred to terminal sires.

Therefore, given the above advantages it is surprising that more terminal sires are not utilised. Many farmers underestimate how many ewes within their flock could be bred to terminal sires. For example, with a flock of 1000 ewes achieving 140% weaning, 700 ewe lambs would be expected to be weaned.

However, if we assume that 30% of ewe lambs are needed as replacements, only 300 ewe lambs are actually needed. This suggests there is clear potential for at least 40 to 50% of ewes to be bred to terminal sires (i.e. 60 to 50% of ewes bred to maternal sires).

This would still allow for scope for 420 to 350 ewes lambs to select from to obtain the 300. If a farmer has confidence in their maternal ram breeder this number should not be an issue. Farmers just need to consider which ewes to breed with their terminal rams.

A trap that many farmers fall for is just putting in the terminal sire for the second cycle. But on most farms, 70 to 85% of ewes are bred successfully in the first 17 days of breeding, limiting the potential numbers of ewes left to conceive to terminal sires.

HHowever, not all terminal sires are the same. Farmers need to ensure their terminal ram breeder has selected for the desired traits and has breeding values.

Just buying a large ram does not mean its lambs will grow fast. The ram might just be big due to the way it was fed on the ram breeder's farm. Farmers should have the confidence to pay a similar price for terminal rams, as their maternal rams, if they come with breeding values.

Terminal rams have the potential to be utilised for a number of years, across many ewes, making them a cost-effective option. However, this will only occur if farmers treat them appropriately.

When farmers buy a new bike or tractor they put it in a shed at night and get it serviced regularly, as they see it as an investment. A ram is also an investment and therefore is no different. They need to be fed well, year-round, and need appropriate animal health plans and monitoring put in place to ensure they achieve good reproductive performance over many seasons.

Paul Kenyon is the Professor of Sheep Husbandry at Massey University and is Head of School of Agriculture and Environment.

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