January 4, 2009

Sheep Farm Husbandry -Preparing for lambing

Sheep, husbandry, lambing, how to measure performance, planning, making preparations, lambing percentage, scanning percentage

By Dr Clive Dalton

The wonder of birth
Lambing time is the busiest time in the sheep farming year. The wonder of birth never fades and it can compensate for some of the exhaustion and frustration regularly experienced by those responsible for lambing. Traditionally, shepherds on both sides of the Scottish border always got a bottle of whisky in (note only one) for lambing time – for medicinal purposes for the lambs of course. In a difficult lambing time, both needed it!

Measuring success - lambing percentage
The key question in assessing a flock is always what’s the “lambing percentage”? Lambing percentage is accepted as the best measure of flock performance and profit. It’s used to assess fertility although fecundity would be a more accurate term. There’s always a bit of confusion between the two terms (see glossary) but this only concerns academics and not farmers. Farmers don’t talk about fecundity.

Farmers know that you can easily fudge flock performance figures by using different calculations of lambing percentage. Look at the list below and work out what each value shows and especially what it hides! Don’t be like the shepherd who proudly told the boss that if he lost another couple of ewes he would have a 100% lambing!
  1. Number of lambs born/100 ewes joined with the ram.
  2. Number of live lambs born/100 ewes joined.
  3. Number of lambs born (dead and alive)/100 ewes mated.
  4. Number of lambs born alive/100 ewes lambing.
  5. Number of lambs docked/100 ewes joined.
  6. Number of lambs weaned/100 ewes joined.
  7. Number of lambs weaned/100 ewes lambing.
  8. Number of lambs weaned/100 ewes joined.
Some estimates hide important facts like the number of barren (dry/dry) ewes or the lambed-and-lost (wet/drys). Some farmers sell the barren ewes after scanning in mid winter and forget to add them into the calculations later.

The true economic performance of a flock is probably best reflected in number 8. It’s what successful farmers call a “true” lambing percentage, because the number of ewes joined is usually the number carried over winter, and every one of those sheep needs to earn its keep.

But if you have to analyse and sort out a low fertility problem in the flock, this value tells you that there is a problem but not where it is – e.g. is it lambs born dead, lamb survival, lamb deaths after docking, barren ewes or poor mothers neglecting lambs?

Scanning percentage
Today it’s possible to calculate a flock’s “scanning percentage”. This is has been a wonderful innovation where a competent scanner for large flocks can predict pregnant or dry (for 35cents/ewe), single, twin, dry (50c/ewe), and single, twin, triplet, dry (80c/ewe). These old prices are roughly double for small flocks. Travel and GST are extra.

But scanning has added frustration too, when farmers see the potential lambs lost between scanning and birth or scanning and docking. Technically the losses are embryos when scanned getting close to being foetuses, but we call them all “lambs” as they are all potential lost lambs. Ewes are normally scanned from 60-70 days of pregnancy and the most common ways of expressing it are these:
  • Number of lambs born/100 lambs scanned
  • Numbers of lambs docked/100 lambs scanned
The second percentage is most commonly used as few farmers with large flocks can count live or dead lambs at birth. So you end up being very frustrated wondering when the lambs died – as embryos or after birth. Embryo losses of 20% are common – with little current knowledge about stopping them.

Finding the cause of poor lambing percentage
If you have to find out why a lambing percentage (LW/EJ) is lower than expected – then here’s a list of things that could be causing it.
  • High ewe losses from joining to lambing, and then from lambing to weaning.
  • High Dry/Dry (barren) ewe numbers.
  • Poor flushing - low ovulation rates.
  • Ewes not cycling or cycling very late.
  • Infertile rams.
  • Not enough rams.
  • Low numbers of multiple births.
  • High losses from scanning to birth.
  • High number of lambs born dead.
  • High lamb losses in the first 3 days after birth.
  • High Wet/Dry ewe numbers.
This list shows where to start and analyse some of these issues. You are going to need to keep extensive records which will take time and effort. Many of these issues can only be studied in research stations and cannot be done on farms. You need to discuss these possible problems with a veterinarian as disease could be implicated in many of them.

Preparing for lambing
A trouble-free lambing depends so much on the weather, but making sure you are well prepared and have all the equipment needed well ahead of time is the other key to success. Here are some suggestions of useful gear to have on hand:
  • Lubricant to ease the passage of lambs that have dried out in the birth canal due to a long labour.
  • Funnel and tube to introduce lubricants into the vagina and uterus when the natural fluids have been lost.
  • Disinfectant for hands before and after helping a ewe to lamb.
  • Surgical rubber gloves to keep hands clean.
  • Packet of scalpel blades and a couple of handles.
  • Clean soft cords or fine ropes.
  • Feeding tube for weak lambs that can’t suck.
  • Covers for lambs in cold wet weather – purchased ones or home made.
  • Heat lamp and a box to warm chilled lambs.
  • Treatment for ewes with milk fever and sleepy sickness
  • Pessaries for ewes that may have metritis (infection of the uterus), usually after a difficult birth. Consult your veterinarian before use.
  • Bearing retainers for ewes with prolapse.
  • Antibiotics for ewes with mastitis. Consult your veterinarian before use.
  • Container to carry all this gear in.
  • Mobile phone and your vet’s office and after hours phone numbers.
It’s essential that equipment be kept clean and boiling for 20 minutes will destroy most bacteria, but cords and ropes that have got dirty should be thrown away and new ones used.

And buy some new comfortable wet weather gear before lambing for yourself,
the family and the staff-
it's a legitimate farm expense

This material is provided in good faith for information purposes only, and the author does not accept any liability to any person for actions taken as a result of the information or advice (or the use of such information or advice) provided in these pages.

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