Beef and sheep notes January 2008

Management of ewes in the six to eight weeks prior to lambing is critical. 75 percent of foetal growth occurs during this time, substantially increasing the ewe’s nutrient requirements. Sheep are extremely sensitive to the quality of forage fed and should never be offered spoiled silage, which can cause listeriosis, or mouldy hay which can lead to abortion.

In the period leading up to lambing the ewe’s rumen capacity decreases rapidly due to the increasing size of the uterus. Forage intake also decreases highlighting the importance of supplementing forage with a high quality concentrate.

A 70 KG twin bearing ewe’s energy requirement will increase from 10MJ of Metabolisable Energy (ME) per day to 17/18 MJ of ME per day during the last six weeks of pregnancy.

While costs have increased markedly this year sheep farmers cannot afford to compromise on the quality of concentrates being fed. Rations for ewes in the six to eight weeks prior to lambing, should be high in protein (16-19 percent) and energy (12 MJ/KG DM), with approximately 30 percent of the protein in an undegradable (by pass) form. A high level of protein is required to ensure:

Vitamin E supplementation within the ration (at least 80-100 iu/KG) is also important for lamb survival. It has been shown to improve lamb vigour at birth and can reduce time to first suckling.

There are two main approaches to the feeding system.

(1) Stepped approach: This is where the amount of concentrate supplementation is increased as pregnancy progresses.

Table 1 shows the concentrate required (KG/day) for a crossbred ewe offered precision chopped silage (10.8 ME, 14 percent Crude Protein)

Table 1

Weeks prior to lambing

When feeding more than 0.4KG/day (1 lb), it is recommended to feed twice per day.

(2) Flat-rate feeding: An alternative to the stepped feeding system is to feed flat-rate at 0.4KG/day for the last six to eight weeks of pregnancy. A flat-rate system:

Aim to have March/April calving cows in body condition score 2 – 2.5 (a light covering of fat around the pelvic bones and across the ribs). Spring calving suckler cows have a low energy and protein requirement during the winter period, which is normally met by feeding silage. Cows must also have an adequate supply of minerals and vitamins if they are to remain healthy and breed successfully. Results of analysis from local silages would suggest that certain important minerals and vitamins are present at levels which are insufficient to meet the animal’s needs. The main ones in this category have been shown to be Selenium, Copper, Zinc, Iodine and Cobalt.

It is important when selecting a dry cow mineral to supplement silage that the correct inclusion rate is considered to ensure that the right level of mineral is fed. Commercial mineral mixes have varying contents of minerals so it is very important to follow the manufacturer’s instructions.

Trace elements are an important part of a mineral mix and deficiencies are often hard to detect. They can influence  fertility and the uptake of some of the more major minerals and vitamins.

When purchasing a mineral supplement remember that cheapest is often not the best guide. Look at the content and the level of inclusion of the different minerals before deciding what is best value for money. If in doubt about mineral status of your herd contact your veterinary surgeon who can arrange for testing of the herd.