Dave Robertson

A North Island farmer I bumped into once told me weaning fat lambs off their mothers was his “velocity money”. Sounded good. Lambs off the place fast and with little inputs is what I assumed he meant.

I have thought about this a bit lately and reasoned that anyone can probably sell all their lambs at weaning at whatever weight, so being pedantic for a moment I might have thought that lamb finishing is more about momentum than velocity.

I foolishly never did physics at high school because my sister said it was boring. I did agriculture instead, which was a complete waste of time but easy marks. If I had done physics at high school one of the first equations I might have learned would be that momentum is the product of velocity (speed) multiplied by mass (weight).

Lamb finishers are very much about maximising the weaning weight of lamb and achieving this quickly before they require shearing, drenching, dipping and fancy feed. You should be all about applying the physics of the momentum equation to lamb finishing.

What are the nitty gritties of the formula? Meat companies might prefer you not to unlock the secret code, because they need year-round supply. But let’s assume not every sheep farmer is motivated by holidays and fast cash. Many of the variables for this lamb momentum theory have already been dialled in for this season.

Ewe body condition at the point of lambing is a fair chunk of it. The body score at set stocking is a measure of all the feeding and decisions made since last weaning. It will determine lamb survival and ewe milk yield – key ingredients for the first half of the lambs’ momentum.

“There are some fairly ordinary sheep about this year” is code for not reaching desired body condition and being rather fatalistic about it. It seems in order to reach the BCS 3 utopia for your ewes, you have to fight the natural imperfections of the seasons, plan seasons ahead with a good handle on what your farm can really grow, and worry incessantly about whether your twinning ewes are getting fed enough each day in winter, and where the quality feed in late pregnancy is coming from.

The second part of this pre-weaning lamb momentum deal is what legume is going to drive lamb growth from five to 10 weeks. There are some great examples of farmers who have re-worked their agronomy towards specialist forages for ewes and lambs. The lucerne grazing systems that Derrick Moot and Doug Avery so passionately advocate for dry-land scenarios are one.

The other is red and white clover stands. Some of the performance of hoggets with lambs at foot on red clover is amazing. It makes me realise we don’t have to accept mediocre 2-tooth performance just because we mate hoggets.

If you’re one of the enlightened farmers who has been swept along by the enthusiasm of a convincing agronomist and are cranking up the numbers in this mass and velocity thing, animal health issues can arise. Dead lambs don’t have the same momentum as others and after more than three you’re getting jumpy about this fancy feed.

Red gut in lambs is a tragedy. Pulpy kidney-type deaths are a preventable pain in the neck. You can create your own flavour of drench resistance really fast and cattle cleaning up can blow up with bloat.

Fibre provision and early clostridial vaccine to lambs, with a strong case for 10-in-1, are solutions to sudden death syndromes. Targeted drenching of ewes with identified un-drenched ewes will help delay drench resistance.

Faecal egg count monitoring lambs at 8-10 weeks for nematodirus and tape worms will help decide if a pre-weaning drench will give you another kilo at weaning, and 100-day rumensin capsules will let you graze cattle on high legume pastures without bloat.

Where sheep farming has gone in my lifetime is staggering – the pace of change and the science and innovation that has propelled a much more efficient production system is world class. Animal and plant genetic options, animal health solutions and technical expertise are out there for you.

If you’re not drafting enough lambs at weaning, find a farmer who is, start a body condition score programme with your peers, make a plan with an agronomist, engage with a vet on a plan that makes your dead-hole redundant. Encourage your kids to do physics at high school. Keep up the momentum.

  • Dave Robertson, BVSc BSc, is a veterinarian at Veterinary Centre Oamaru