Managing the growth of ewe weaners
Elders livestock production coordinator, Rob Inglis recently unveiled the results of a trial, looking specifically at what are the long-term effects of the weight of a ewe during puberty.
Rob and the team analysed the net reproductive rate (NRR) over the life of the ewe amongst other key metrics.
Start with a strong foundation
The trial started with sound genetics across seven trial sites, whereby animals with obvious conformational or phenotypic defects were removed. When anyone questions when to cull ewe weaners, Rob suggests if they are underweight at 12 months old it’s probably best to sell them.
“If ewes are below the target weight at 12 months old they are more likely to be compromised as breeders,” he explained.
Weight and nutrition go hand in hand
The effect of weight was evident even at the first joining, where light ewes scanned at 30 per cent (pc) and heavy ewes scanned at 50pc.
Rob explained that nutritional management begins at weaning.
“Generally speaking, differential feeding (different diets for separate weight groups) begins at weaning or 14 weeks of age,” he said.
“Best practice would start weight management at scanning. Twin and single bearing ewes would be allocated feed based on their pregnancy status. Allocating better feed to the twin ewes, elicits better milk production during lactation, which in turn means better growth rates.”
Access to high energy feed for first time mothers at joining and with lambs at foot is especially important for ewes with twins. Peak energy requirement occurs in early-lactation (day 21), ideally 20MJ/DSE for single bearing ewes and 27MJ/DSE for twin bearing ewes.
Rob explained why it’s important for twin bearing ewes and their lambs to have access to the highest energy feed.
“The twin bearing ewe will draw more condition ‘off her back’. This has two obvious implications:
- Twin lambs will source a higher proportion of their diet from pasture from four weeks of age and onward, therefore pasture quality for twins must be much higher.
- Twin bearing ewes will lose more condition during lactation and will therefore require more time on better quality feed in order to regain it.”
The bottom line
The results of the trial concluded that heavy ewe weaners produced four more lambs over their lifetime compared to light ewe weaners.
Rob breaks it down into approximate dollar terms at today’s prices, assuming an equal spread of males and females:
- 2 x wether lambs @ 22 kilograms carcass weight x 9 kg = $396 + $30 skins = $426
- 2 x ewes kept for 5 years = 5 wool cuts @ 6 kg x $9 = $270
- Total extra income = $696 per ewe.
- Added to this is the long genetic improvement ergo additional income realized through greater selection pressure afforded on the ewe flock.
Rob’s five steps for weaning time
1. Imprinting – at least five feeds or two weeks prior to weaning
2. Draft by weight – into three groups: heavy, medium and light.
3. Animal health treatments – vaccines, drench, vitamin and mineral supplements according to weight class.
4. Differential feeding – balance energy and protein according to weight
5. Monitor weights – weigh regularly to ensure growth trajectory, light lambs need a higher growth rate per day.
- Minimum growth rate for top 25pc (by weight) = 50g/day
- Minimum growth rate for bottom 25pc = 100g/day
Take the guess work out of weaning
In conclusion Rob explained the importance of accuracy.
“Buy or borrow some scales,” he said.
“I don’t care how good a judge of sheep someone thinks they are; it’s impossible to sort lambs into weight groups accurately by eye.
“Skeletal mass is the critical factor. Bone is the primary repository for the key minerals required for lactation, namely calcium, ipso facto it has a profound influence on the ewe’s future reproductive performance.
“There are a number of factors which contribute to skeletal development, which is a whole new discussion. The point is, it’s nigh on impossible to make an accurate visual assessment on skeletal mass.”
Special opportunity to learn more
Need tailored advice for your ewe weaners? Contact your local livestock production advisor.