The August Article of the Month is an invited review entitled ‘Breeding objectives for sheep should be customised depending on variation in pasture growth across years’

The type of sheep that farmers breed for need to be suited to the farm they are managed on. To pick the best type of sheep, farmers need to know how their sheep can make more money for their farm. The profit of farms depends a lot on how much pasture grows on the farm. In farms in Western Australia there are big differences in the amount of pasture that grows depending on the location of the farm. Therefore, we investigated how variation in the amount of pasture across 11 years and within these years for different parts of Western Australia affects the type of sheep farmers should have.

To work out the type of sheep farmers should have we modelled farms with Merino sheep bred for wool and meat for 10 regions in Western Australia. These regions are in the Mediterranean parts of Western Australia, which have a drought period during summer and autumn and pasture growth in winter and spring. These 10 regions were located in a line from near the coast with high rainfall to inland with low rainfall. The total amount of pasture that grew decreased from the coast towards the inland and was more uncertain between years. This uncertainty meant some years had longer drought periods than others. Therefore, pasture growth became more reliable as you travel from inland towards the coast.

We found there were two types of sheep for Western Australian farmers. Surprisingly, farmers in areas with high reliability for pasture growth should breed for the same type of sheep as farmers in areas with low reliability. These sheep should be bigger and wean more lambs. Alternatively, farmers in areas with medium reliability of pasture growth should breed for a different type of sheep that have better quality wool.

The reason that high and low regions should have the same type of sheep is because the drought periods are the critical time of the year. This is obvious for the low reliability region where sheep should be adapted to drought. For the high reliability regions, the periods of drought were shorter. Also, there was a lot more pasture growing in spring, too much for the sheep to eat. Farmers want the sheep to eat as much pasture as possible, since it is essentially free food. In these regions the drought period was limiting the amount of sheep the farmer could have. Therefore, high and low pasture growth regions require big sheep that could eat more dry pasture during droughts, and that have more lambs which have the highest energy requirements during spring. Then in high reliability regions having more sheep means eating more pasture during spring.

Therefore, farmers will need to adapt the type of sheep they breed for based on their region. Additionally, breeders can provide farmers from high and low reliability regions with the same type of sheep. This research is relevant to farmers all over the world, especially as the effects of climate change increase.

This paper is freely available for one month here
Authors: G. Rose, H. A. Mulder, A. N. Thompson, J. H. J. van der Werf and J. A. M. van Arendonk

The animal Article of the Month is selected by the Editor-in-Chief and is freely available for one month

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