The key indicator of ewe flock performance is the number of kilograms of lambs weaned per ewe mated. This is determined by two factors. Firstly, the number of lambs weaned and secondly the lamb weaning weight.
With drought affecting many areas of New Zealand during the summer and autumn, mating performance wasn’t as good as it could have been, meaning the number of lambs we are likely to have by the time we get to weaning will be down.
Also, many ewes will be lambed in less than ideal condition or on very low pasture covers. This has a flow-on effect through poor milk production to their lambs, leading to lower weaning weights. This means that the overall kgs of lamb weaned per ewe mated is likely to be down. On the brighter side, the lower lamb crop is likely to keep lamb prices up through procurement competition. This means we need to maximise the potential of every lamb we have to realise their value.
Zoetis consulting veterinarian Dr Clive Bingham shares some key areas for farmers to consider to get their lambs thriving – disease prevention, mineral supplementation, feeding and protection from internal and external parasites.
If a ewe is in poor condition she is less likely to have mounted a good immune response to her pre-lamb vaccination, meaning less maternal antibodies are passed on to the lambs once they suckle. Lower levels of passive protection mean the lambs will become susceptible to disease sooner.
A field trial looking at lamb loss periods from docking through to pre-lambing found the greatest periods of lamb loss occurred after docking and weaning 1.
It is therefore important that we begin our clostridial vaccination programs as early as possible, with the initial sensitiser dose given at docking/tailing and complete the booster vaccination prior to or at weaning. This will maximise the lamb’s chance of developing its own immunity before their maternal antibodies are all gone, and in the case of pulpy kidney, they are protected before the period of greatest risk which is around weaning.
Even on farms where trace element deficiencies (selenium and/or cobalt) are not usually seen, deficiencies can occur where ewes are chronically underfed, and this can pass onto their lambs.
Consider supplementation of lambs at docking with vitamin B12 and/or selenium to top up their levels. This can be done in conjunction with the clostridial vaccination of the lambs using Ultravac® 5 + 1 SeB12 at docking.
Ewes that produce less milk will have lambs that are smaller at weaning. This means more lambs will be retained on the farm for longer. Depending on the timing of shearing, consideration should be given to treating the lambs at docking to prevent flystrike. Consider a long-acting treatment (e.g. StrikeForce®-S) sprayed over the tail stump and scrotum to protect them up to shearing.
When ewes don’t produce as much milk or lactate for as long, thought should be given to weaning lambs early onto a high-quality diet. This can be pasture with a high legume component or a specialist finishing crop. These crops not only provide better nutrition so the lambs grow faster, but also aid in parasite control by decreasing exposure of the lambs to the infective parasite larvae.
Poor condition lambing ewes are likely to lay down more contamination on the areas they were set stocked on. Combined with less milk production, this means that contaminated pastures will become a greater proportion of the lambs diet sooner, compared to better fed milk lambs. It is recommended that you start taking fecal egg count samples (FEC’s) from these lambs prior to weaning to detect any early buildup of parasites that will slow down lamb growth rates. For lambs weaned onto pasture it is important that they are weaned onto low contamination areas of the farm where no ewes have lambed in order to promote optimal lamb growth. Monitor the lambs on these areas using FEC’s to balance your drench inputs with the level of pasture contamination. Also ensure you do a drench check early in the season to ensure you are using an effective drench and not contaminating your farm with drench resistant worms.
Lambs are the main contaminators on the farm. Removing these young susceptible stock as quickly as you can will help decrease the worm burden and therefore help improve overall health for ewes and the remaining lambs.
Although you cannot fully compensate for low lamb numbers, working on maximising the survival and growth of the lambs that you do have, goes a long way to improving your bottom line and allows you to take full advantage of any better store or schedule prices.
Zoetis New Zealand Limited. Tel: 0800 963 847; www.zoetis.co.nz. Ultravac and Strikeforce are registered trade marks of Zoetis. ACVM Nos. A11349, A11606
1. Bingham, C. M. & Hodge, A. (2022) Lamb mortality and clostridial disease. New Zealand Veterinary Journal 70 (1) 49-54.
