The intricacies of pre-lamb ewe nutrition was the topic for discussion when members of Beef + Lamb New Zealand’s Northern South Island Lamb Survivability Focus Group gathered together in late June.
While all 12 members of this group run very different farming operations – from extensive hill country through to high performance intensive breeding and finishing, all share a common determination to reduce their lamb wastage.
The group is facilitated by B+LNZ’s Sarah O’Connell and discussion that day was led by subject matter experts Dr Charlotte Westwood, a veterinary nutritionist and Stu Hunter, a technical extension agronomist, both from PGG Wrightson Seeds.
Charlotte set the scene by saying “normal” lamb losses between scanning and tailing sit at between 15-20 percent, so one in every five lambs scanned doesn’t make it to tailing. This highlights the opportunity available to reduce wastage.
Ewe nutrition has a huge influence on lamb survival and this all starts at mating.
Ideally, ewes should be at Body Condition Score (BCS) of 3.0 from tupping onwards. Any loss of BCS will influence ovulation, conception and implantation, placental development- which is complete by 80-90 days post-mating - and foetal and udder development. The most important period for foetal and udder development is 115-145 days after mating.
Ewes not receiving the right nutrition during each key stage of the post-mating through to pre-lambing period will be producing smaller lambs with less heat-generating brown fat. These lambs will have less oxygen at birth and low blood glucose. The ewe’s colostrum will also be compromised with less fat and fewer or no antibodies. Small lambs are less likely to survive their first 24-48 hours, and triplet lambs are most at risk, because being smaller, they have a greater surface area from which to lose heat.
While placental development is set by day 90, Charlotte says there is still a window of opportunity to lift the condition of lighter ewes after scanning to influence lamb survival. For several farmers in the Focus Group, this was where they saw they could get the best return on their feed investment.
To lift the bottom-end ewes pre-lambing, they require a minimum pasture height of 4cm or 1400 kgDM/ha (that is high quality green material) to lift their BCS by 0.5 in three weeks.
Energy, energy and more energy
Charlotte stressed that energy was almost always the most limiting factor in all in-lamb ewes, but particularly in multiple-bearing ewes.
It is the combination of feed quantity and quality that are the most important factors for in-lamb ewes and Charlotte urges farmers to focus on these factors before being caught up in minerals and trace elements.
“Don’t sweat the small stuff until the big stuff is under control.”
While some trace elements such as selenium are important, a simple treatment can “make the issue go away” where feed management can be much more important opportunity and have a greater impact on lamb survival.
Put together a feed budget
Charlotte strongly urges farmers to put together a feed budget. This can either be a comprehensive, whole farm feed budget using tools such as Farmax- or a very basic spreadsheet for just part of the farm for a short period e.g. between set-stocking and tailing. But whatever version is used, Charlotte encourages farmers to run a best case and worst-case scenario to ensure all bases are covered- particularly if spring growth is slow to come away.
“Knowing what’s under foot and what you will grow over the next five to six weeks will give you an idea of whether you will drop below minimum residuals of 1,400 kgDM/ha needed for at-risk ewes”.
When calculating demand, factors such as energy for walking and grazing needs to be taken into account along with BCS (whether ewes need to gain or maintain) along with the pregnancy demands in the last six weeks of pregnancy. Over this time, ewes will gain 8-18kg of lambs, uterus, fluids and udder. FeedSmart Feed table for pregnant ewes (PDF, 60.8KB).
Ewes carrying multiples have a compressed rumen and while the rumen “squash factor” can be similar for both twin and triplet-bearing ewes, the ewes carrying triplets require 70 percent more energy than ewes carrying singles and 30-40 percent more energy than those carrying twins. This reinforces the importance of making every mouthful matter for triplet bearing ewes.
Stu Hunter encouraged the group to consider growing a winter active, high feed value crop, such as an Italian ryegrass, as part of their pasture renovation programme.
This gives farmers a forage option for in-lamb ewes with a high requirement for energy and protein in that late pregnancy period.
Grain and forage crops
Cereal grain is more energy dense than pasture and is therefore an ideal supplement for in-lamb ewes where there is insufficient pasture to meet their needs. High in starch, grain lifts blood glucose in both ewes and lambs. Grain use needs to be justified on the basis of cost, and also the risks associated with mismothering of lambs if ewes are disrupted by grain feeding through lambing.
Demand for crude protein increases through pregnancy, particularly in hoggets, multiple-bearing two-tooths and lighter condition ewes (although total energy remains the key priority).
Bulb dominant crops (such as fodder beet) tend to be low in protein (most of the protein is in the leaf) so protein deficiency can be a risk, particularly for ewes in later pregnancy. Swede crops tend to contain more protein than fodder beet crops, but much depends on the ratio of leaf to bulb present for each crop type.
While leafy kale and forage rape are higher in protein and pose less of a risk for protein deficiency than fodder beet, autumn-saved pasture has the highest levels of crude protein, particularly where pasture contains high quality grass and legumes and nitrogen fertiliser has been applied.
Charlotte encourages farmers to use the “snap test” to test kale and rape crops. Don’t expect ewes to eat below the point where the stem can be snapped as ewes can struggle to eat the woody base of the plant.
Ewes should always be moved from kale, swede or rape crops and set stocked back onto pasture ideally at least two weeks before the start of lambing.
Use single bearing ewes as lever to pull
At set-stocking the focus must be on multiple-bearing ewes- giving them feed, shelter and space.
Several of the farmers in the Focus Group were aiming for admirable pre-lamb pasture covers of 2,000 kgDM/ha to set-stock onto.
Charlotte says this gives them 600kgDM/ha to work with, assuming they will not graze below 1,400 kgDM/ha, but will gain additional feed every day as pasture starts to come away.
When feed is tight, Charlotte suggests spreading the twin and triplet-bearing ewes out on pasture at a relatively lower stocking rate, and supplementary feeding the singles because mismothering of single lambs is less likely should ewes be disrupted by the feed out process.
Other resources
- Lamb survival resources.
- Early- to late-pregnancy nutritional management of ewes, with Professor Paul Kenyon, Massey University.
About B+LNZ’s Focus Groups
B+LNZ Focus Groups are a small group learning initiative introduced into the extension programme as part of B+LNZ’s refreshed strategy.
They are topic focused, and outcomes driven, providing farmers with the opportunity to learn from other members and subject matter experts. These groups are deliberately kept small to ensure everyone gets a chance to share their experiences and learn from each other.
Each B+LNZ Focus Group is a closed for the duration, usually over two years, with eight group days in total. The group activity is designed to learn, identify opportunities and then identify actions to take ‘back home’ – delivering real value now and into the future.
A Focus Group is free to all B+LNZ levy payers and their employees; these groups are closed groups with members committing to the full group journey.