Sheep producers must use their scanning results to group and feed pregnant ewes accordingly – and not just as a predictor of lambing percentage. That’s the message from Cargill’s technical sales manager Georgina Croxford, who gave Rachael Porter some nutrition pointers for pregnant ewes.
Georgina (right) explains that many producers do scan their flocks to determine if ewes are expecting single, twin or triplet lambs, “but many don’t use that information to group, feed and manage their ewes in the run up to lambing.”
She adds that this year’s early scanning results are good, showing a high number of multiples (January lambing flocks). But this is just the starting point for a successful lambing season.
Feeding ewes during the final six weeks of pregnancy is particularly important because 70 per cent of foetal growth takes place during this period, as well as udder development and colostrum production. “Paying extra attention to ewe nutrition at this time is key,” Georgina explains.
“During this period the ewe’s energy and protein requirements increase rapidly – more than doubling for ewes with twins. But as the lambs grow, the ewe’s ability to eat bulk reduces. Therefore, the nutrient density of the ration must be increased gradually to keep pace with foetal requirements.
“The best way to achieve this is to group and feed ewes according to scanning results and their condition score.”
Ideally ewes should lamb at a body condition score (BCS) of 3–3.5. This should also be the condition they’re tupped at, to optimise fertility and conception/lambing percentage.
“Feeding ewes to put on condition after tupping is a big no,” Georgina stresses. “It’s not good for the ewe, the lambs, or colostrum quality.”
So, it’s important to prevent a change in ewe body condition towards the end of pregnancy, because this can lead to depressed colostrum production – both in terms of its quantity and quality, or immunoglobulin (IgG) concentration.
Trials have shown that between 15 and 20 per cent of lamb mortality, 24-hours post-partum, is preventable through provision of sufficient quantity (150–210ml/kg of birth weight) of high quality colostrum (IgG > 50g/L).
“Key drivers for quality ewe colostrum production are managing body reserve mobilisation, breed, age, gestation length, and lamb birth weight,” Georgina adds. “If good quality, plentiful colostrum is not available, a colostrum enhancer or a colostrum replacer must be fed. Colostrum is the most important feed to an animal.”
When it comes to ration formulation, the starting point is to analyse silage. “There’s a lot more silage around this year, compared to 2018, and if producers are going to utilise this effectively and feed pregnant ewes a balanced ration, then they need to know the protein, energy, fibre, and mineral content of their forage.
“They can then supplement this with ewe concentrates or cereals, as well as minerals, to meet the ewes’ nutritional requirements.”
Georgina adds that a good quality mineral – containing selenium and vitamin E to support antioxidant status of the ewe and good quality colostrum production – is vital.
“How we manage our ewes during pregnancy will affect not only their performance, but that of their offspring too,” says Georgina. “This is an epigenetic effect.”
For example, if the ewe suffers nutritional stress during the final few weeks of pregnancy, it will impact on her offspring’s fertility when they join the breeding herd.
“So, feeding ewes in pregnancy has a longer-term affect. It’s not just about the ewe and her colostrum. It also impacts on the future productivity of her lambs. Paying more attention to pregnant ewe nutrition will pay dividends in the short and long term.”