Lamb survival and foetal growth rates improve when both the energy and protein requirements of the pregnant ewe are met, especially from mid-pregnancy.

If you feel that your lamb losses at birth are greater than expected, or your weaning weights are lower than expected, then it could be due to an unbalanced ewe diet. Once energy needs are met, the protein content within the ewe’s diet helps drive its performance.

To calculate the ewe’s energy needs, you need to know:

1. The body weight of the ewe mob, its average and the range at tupping.
2. The body condition score of the ewe mob, its average and the range.
3. The quantity of pasture, crop and supplemental feed given to the mob.
4. The quality of pasture dead matter and protein as a percentage of the crop and supplements fed to the mob.
5. The pasture and crop growth over the winter period.
6. The paddock and/or crop break size.

Armed with the answers you can create an honest diet. As pregnancy advances, the increased energy demand can be calculated using tables available in many farming publications.

Providing sufficient protein in the diet increases the total dry matter intake as well as meeting the energy needs in animals. If you find that growth rates of hoggets, yearling cattle or deer are lower than you expect, then check the protein content of their diet. A blood sample helps determine the urea content which indicates if a protein deficiency exists. This can change rapidly though, so do not alter the diet of the animals before testing.

Last winter, I completed blood tests on some pregnant ewe hoggets and found they were protein deficient. After a change of diet for two weeks, their blood levels were all near the top end of the sufficient range and the farmer commented that their condition had improved significantly.

In a grass wintering system, dead matter can be assessed. The dead matter needs to be removed from the feed budget as the ewes will not eat it, but rather trample on it.

The protein content in a crop is determined by analysing both the bulb and leaf with fodder beet and swedes and the leaf and stem in kale and rape. High-yielding crops either have large bulbs or thick stems, both of which have a lower protein content so the ratio of leaf to bulb or stem is important when making these calculations. Remember to test your feed supplements too.

Calculating the protein content of the diet allows you to remedy any deficiencies using a supplement which can also be an important source of fibre. As well, break-feeding crops on a more frequent basis allows for a better balance of leaf and bulb intake.

To discuss how to test the condition of your animals as well as your crops, and to learn more about feed supplements to improve protein levels in stock, contact your local PGG Wrightson Technical Field Representative.