Winter shearing delivers increases in lamb birth weight

EWES AT Lyons were shorn in the third week of January in preparation for lambing in mid-March.

There are a number of benefits of this management technique but perhaps most telling is an increase in lamb birth weight of approximately 0.5 kg per lamb.

When ewes are housed the duration of their pregnancy is shortened by around two days. When these housed ewes are shorn the duration of their pregnancy returns to the average of 147 days.

Other responses we see from winter shearing are increased intake and potential to increase stocking density in the shed.

We are now in the final two months of pregnancy for the flock, and this is one of the key periods in the production cycle.

A number of very important events are taking place in this window including approximately 80-85pc of foetal development takes place, the mammary gland is conditioned for lactation (largely in the final three weeks of pregnancy) and the ewes intake capacity is declining.

Our objective at Lyons is to maintain ewe body condition score (BCS) during the final six to eight weeks of pregnancy, and BCS is something we monitor continually throughout the year.

When the ewe is turned out to grass with lambs at foot, there is a large demand on her system to produce milk for her lamb(s).

Having some body reserves available for mobilisation is key to allow her to produce milk and to take advantage of the high crude protein content in spring grass.

For a twin bearing ewe, energy demand will increase by 70-80pc in the final two months of pregnancy. If we take a ewe live-weight of 75 kg then she requires 10.5 MJ of metabolisable energy to meet her maintenance requirements.

Let’s assume this ewe is carrying twins and each lamb will be born at 5kg live weight, then in the final week of pregnancy she will need an additional 9MJ of metabolisable energy to meet the growth requirements of the lambs.

Our approach is to meet these energy requirements from the diet as opposed to having the ewe mobilising body reserves to do so.

Silage analysis

The starting point for our feeding program is silage analysis.

Silage is a very variable product and depending on average nutritional values in place of forage analysis can lead to under (or in rare circumstances) over feeding. The silage being fed to the ewes at the moment, has a DM content of 26pc a DMD value of 71pc, a metabolisable energy content of 10.8 MJ and a crude protein content of 15.1pc.

With mean lambing date predicted to be March 13th the only animals receiving concentrate supplementation at the moment are the ewe lambs and the triplet bearing ewes.

These are receiving 250gs per day fresh weight of an energy supplement. We will introduce a 14pc crude protein coarse ration to these animals later this week, and begin supplementation of the twin bearing ewes early next week.

Lameness which can often be an issue in straw bedded flocks is running at 3pc currently.

Lame ewes were separated, treated and housed separately at the time of housing.

Any ewes which have presented with lameness subsequent to housing were isolated, diagnosed and treated appropriately.

Routine management of the flock for lameness control consists of foot-bathing every two weeks, and maintenance of dry under foot conditions. The reasonable high dry matter silage is helping in this regard.

Also passing the ewes through the race every two weeks allows a good opportunity to assess BCS on a sample of the ewes and advises us on the adequacy of the feeding program.

Ewes will receive their booster clostridial vaccination approximately four weeks before lambing.

Assoc. Prof. Tommy Boland is a lecturer in Sheep Production at Lyons Farm, University College Dublin. @Pallastb tommy.boland@ucd.ie