Ewe BCS going into Breeding

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We all know the importance of having ewes at target body condition score at key times of the year – if they are at target at mating, they are more likely to conceive, thus improving scanning percentages, and more likely to be at target at lambing, which increases colostrum production, lamb survival, increases lamb growth rates and weaning weights and has many flow on effects. In a dry year this is even more important, as the feed needed to get ewes to target BCS is a rare and precious resource. This is why looking at the individual ewe BCS is so important, not the flock average.

Ewe BCS target = 3.0 all year round

Key times of the year to monitor this are:

  • Weaning

  • Pre-mate

  • Scanning

  • Pre-lamb

Some of these times are more convenient than others – for example if you’re putting your hand on them to push them onto the scanning trailer, or giving pre-mate minerals. You don’t have to monitor ewes at each of these times, maybe just a couple, and you don’t have to condition score them precisely. The key is to identify and raise the bottom percentage of the flock so that you can put extra feed resources into them, not into those already at target.

1. There is a real benefit to lifting your lighter ewes

An increase of one BCS from 2.0 to 3.0 has been shown to increase scanning percentage by 15%, lamb survival 5%, lamb weaning weights 5% - analysis in 2010/11 gave an gross margin per ewe of $13 (over summer).

2. There is a “law of diminishing returns”

You will get massive relative gains in ewe performance as individual ewes go from a BCS of say 1 ½ - 2 and so on. This trend continues, but the curve becomes less steep – once ewe BCS reaches 3 – 3.5, there is minimal increase in production, whether it be increases in conception rate, lamb growth rates, or other effects of improved BCS. This is why there is no advantage to feeding ewes to gain condition over target BCS.

3. Feeding fatter ewes is inefficient

In addition to this feed being essentially wasted, as it will not improve production, it is also used very inefficiently. It takes a lot more energy – 351MJ – to go from 3.5 to 4.0 than it does to go from 2.0 to 2.5 – only 71MJ. So you don’t even have to put that many kg DM into those light ewes to bring them up to target, emphasising the importance of being able to separate them out and allocate precious feed to only those that need it.

Take home messages – putting precious feed into ewes at target will not improve production. Focus on lifting the individual BCS of lighter ewes at the bottom of your flock. Now is one of the key times you can do this to have a big impact on scanning, lambing, and weaning outcomes.