Getting silage for pregnant sheep analysed will help ensure pre-lambing ewes get the appropriate nutrients in the most cost-effective diets.
Rosie Miller, ruminant specialist with Trouw Nutrition GB, says managing ewe nutrition in the run up to lambing is an important step towards a successful lamb crop, but adds without a representative silage analysis, it will be impossible to ensure ewes are fed correctly.
She says: “The starting point of any ration is good quality forage, with compound feed or straights fed alongside, but to develop an effective diet you have to know how good the forage is so the other feeds supplement it correctly to meet the total requirements of the ewe.
“Forage is an important part of pre-lambing diets at what is a crucial stage for the ewe and the lamb crop. Assuming an average analysis as the basis for supplementation decisions could result in ewes being over- or under-fed.”
Ms Miller says the consequence of over-feeding will be higher feed costs, an increased risk of twin lamb disease and prolapse and increased feed intakes post-lambing.
Under-feeding means ewes may lose excess body condition, have poorer colostrum quality and yields, reduced milk yields, low lamb birth weights and increased mortality. Early lamb growth will also be compromised.
She says the variation in silage quality can be significant. From a review of grass silages produced for sheep in winter 2016/17, Ms Miller says the average energy content was 9.8 MJ/kg DM, while the top forages had an energy content of 10.8 MJ/kg DM.
“This difference will have a marked impact on performance and possible costs. With improving quality, forage intakes will increase and farmers can take advantage by maintaining a high forage to concentrate ratio in the diet to help avoid issues such as acidosis.
“Conversely, intake of poorer quality forage will be compromised, which could result in a lower energy supply than anticipated. So one aim should be to maximise the quality of grass silage made on sheep farms.
“However, for this season the forage is made, so it is key to utilise forage analysis so ewes can be rationed accurately.
“A 70kg twin-bearing ewe requires 15.3 MJ per day at three weeks pre-lambing. Ewes fed the average sheep silage last year would have required 0.6kg/day of an 11.8 MJ compound feed to meet requirements, but if they were on the best silage, this would drop to 0.43kg/day. Without a silage analysis, it is impossible to balance the forage correctly.
“Using our example, if the farmer assumed he was using average quality silage and supplemented accordingly, but actually had better quality feed, ewes would be being over-fed by 170g/day.
“For a 350-ewe flock, this is 60kg of concentrates per day being fed unnecessarily at a cost of about £13/day. As well as pushing up costs, there is a risk of overweight lambs and more problems at lambing.”
Ms Miller says samples can be analysed and back on-farm in a few days, meaning diets can be reviewed and fine-tuned to improve performance and control costs.