How to get sheep reproduction snowballing for you

Dr Mark Ferguson, March 16, 2020

Crossbred ewes and lambs. Image – MLA.

HAVING more lambs weaned per ewe put to the ram has a multitude of benefits to a sheep enterprise.

The beautiful thing is that these benefits are compounding or in other words these benefits snowball.

If you are running a sheep enterprise that has a significant component of breeding ewes in it, improving reproduction rates should be high on your list of jobs to do. Until you’ve farmed with high weaning percentages it is hard to imagine what it would be like. What we see time and time again is the power it brings to a sheep enterprise.

Firstly, there is of course the increase in number of store or prime stock that can be sold as lambs. But it doesn’t end there; the next thing that you will notice is that your flock age profile starts to tighten up. If your weaning percentages are low, you are flat out trying to scrape together a group of replacement females and you find yourself keeping ewes on farm for a year or two longer than would be ideal. The mortality rate in these old ewes is considerably higher than their younger equivalents which is a direct cost to the business. They also produce less wool of lower quality than their younger counterparts.

Lift weaning rates for flexibility

As your weaning percentages continue to climb you find yourself with a lot more flexibility in your system. You have excess ewes for the first time in your farming career, you are then spoilt for choice. You can diversify your sheep business and mate some ewes to a terminal sire. You can choose to sell ewes as capital stock at a year younger than you historically would have. You can increase the selection pressure on your adult ewes and sell any ewes that aren’t meeting your production parameters.

You also get enormous flexibility from being able to sell down ewe numbers in tough periods, knowing that flock numbers can quickly rebound as soon as the good times return. This kind of flexibility becomes more and more important in areas with a more variable climate.

I can’t remember where I heard the quote but it went along the lines of “keep the impacts of the drought to the year of the drought”. In genotypes that have a low reproductive potential, this is almost impossible to achieve; however, the opposite is true for ewes with high reproductive potential. It is only necessary to retain the absolute core breeding ewes in the knowledge that numbers can quickly be increased, particularly if mating them as ewe lambs (hoggets NZ).

High reproduction benefits ‘snowball’

Merino ewe with twin lambs. Image – Mark Ferguson, nexTgen Agri.

The increase in reproduction rate also has a major impact on the selection pressure you are able to apply on replacement females. The ability to sell ewes that don’t meet your breeding objective as young prime ewes is an enormous benefit of improving reproduction rates. As weaning percentages improve, the proportion of young females that need to be retained and mated to maternal or Merino rams reduces. The criteria to be retained can be made increasingly difficult so that only the top end ewes are making it into the breeding flock.

The greatest thing is that this whole thing snowballs; the better the reproduction gets, the younger the flock gets and the higher the selection pressure is on replacement females. This results in better ewes that receive an even higher scrutiny to get selected as a replacement ewe. The whole while turning off many more surplus lambs and surplus breeding ewes and shearing more sheep that produce more wool.

Buy rams for reproduction value

Sustainably increasing reproduction rates includes making sure you have the best genetics for the job as well as carefully managing their nutrition to ensure scanning percentages and lamb survival are as good as they can be for the genotype you are farming.

When you are buying your rams, how much do you consider the productive potential of their daughters? Do they have a breeding value for reproduction available on them? Do you look at it? What weighting do you put on it?

If you find yourself having vague answers to these questions, it is time to reconsider. The reality is that most people in the industry either do not have the information presented to them or don’t look at it. One of the excuses for this can be that it is lowly heritable, “So why should I worry about it?”  Yes, the heritability of reproduction is low (roughly 5% of the variation in ewe reproduction is due to genetics), but the variability is enormous, so there is still plenty of opportunity to make gain.

Some people will only buy twin born rams, this does have some impact but nowhere near the same amount of impact as actually selecting on the breeding values for reproduction.

Manage ewes to their genetic potential

The other half of this equation is making sure you manage the ewes to express their genetic potential. At the start of the reproduction cycle this means ensuring your ewes hit the ram in condition score three and on a slightly rising plane of nutrition.  The focus is then on ensuring that ewes that have conceived with twins or triplets are looked after and lamb above condition score three, wherever possible. We’ll talk more about the nutritional aspects in future articles.

  • Dr Mark Ferguson is a geneticist with NextGen Agri



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  1. Daniel Claro, March 16, 2020

    Quite right, till 150 percent prolificacy, where roughly 50pc of ewes give single lambs and the rest give twins. Only 2 or 3pc triplets. Beyond that, the proportion of twins is maintained, but triplets increases as sharply as singles decrease. With 190pc prolificacy, only 25pc of birth are singles; 55pc are twins and 20pc of ewes will lamb triplets. The ideal will be to have no triplets, but that is impossible with very high prolificacy. To rear triplets is almost impossible in an extensive way of sheep farming.

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