Late-pregnancy nutrition: Check your protein levels when supplementing ewes
Late-pregnancy nutrition is an important stage in the lamb production system on many sheep farms as it affects the subsequent performance of both the ewe and her offspring.
Flocks lambing during March should be monitoring feeding from the start of January until lambing in order to achieve optimum performance.
Silage will form the basis of the diet offered to ewes during late pregnancy on many sheep farms across the country and, therefore, it’s important that it’s high quality.
However, the quality of silage can be highly variable from farm-to-farm. Most farms will have moderately good silage, but this will need to be supplemented.
Silage alone – in most cases – will not meet the ewes nutritional requirements in late pregnancy for energy and protein.
In addition, the increasing development of the unborn lambs will decrease the intake capacity of the ewe. In essence, the lambs will occupy more space inside the ewe which will impede her ability to intake feed, particularly silage.
For these reasons supplementary concentrates, in addition to silage, will be required to supply the essential nutrients for the ewe to meet her demands during late pregnancy.
On most farms the level of concentrate supplementation required will be determined by silage (or other forage) quality.
However, there are other factors that determine the amount of supplementary concentrates offered in addition to grass silage during late pregnancy such as: ewe litter size; the number of weeks before lambing; and ewe body condition score (BCS).
Completing a silage analysis is important as the report will allow you to make decisions on the levels of concentrate supplementation required during late pregnancy.
Protein is of particular importance as it effects colostrum production and lamb birth weight.
When offering low crude protein (CP) silage to twin bearing ewes, the concentrate should be formulated to contain 18-19% CP.
According to research – on average – a twin bearing ewe is estimated to have a daily CP requirement of 200g/day during the last three weeks of pregnancy.
In this case the dietary CP supply to the ewe is 203g/day and should meet her CP requirements. However, it is important to consider the dietary protein source.
Soybean meal is an excellent source of rumen undegradable protein and it is advisable to ensure that soybean meal accounts for a high proportion of the protein present within the concentrate.
Teagasc research has shown that the source of the protein in the concentrate is more important that the CP percentage.
Two concentrates were formulated to have 12.4 MJ/kg DM and 18% CP (as fed). The different protein sources in the two concentrates were soybean meal and a mixture of by-products (rapeseed, maize distillers and maize gluten).
Lambs born to ewes that had been offered the soybean-based concentrate produced lambs that were 0.3kg and 0.9kg heavier at birth and weaning, respectively.
Research from UCD (University College Dublin) has shown that feeding a soybean-based concentrate pre-lambing increased colostrum yield in the first 18 hours post lambing.
As a result of the increased colostrum yield the lamb’s absorption of antibodies from colostrum during the first 24 hours post lambing increased.