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Season of shearing impacts flock profitability


Ewes are normally shorn once annually in early summer. However many producers are now shearing either at housing in December or prior to joining in September. Sheep researcher Tim Keady presents results from studies at Athenry on how season of shearing affects subsequent animal performance.

Main messages

Shearing ewes at housing: 

  • increases lamb birth weight by 0.6 kg
  • has no impact on lambing difficulty
  • increases lamb weaning weight by 1.9 kg
  • reduces lamb age at slaughter by approximately 2 weeks
  • enables more ewes to be housed in a given area

Shearing one month prior to joining resulted in approximately 50% of the benefit in lamb birth weight observed when shearing was at housing.

Introduction

At current market price the value of a fleece of wool will pay for approximately 18% of the cost of shearing.  Consequently, to get a return on their investment producers must look at impact of time of year of shearing on animal performance, particularly of lambs, to recuperate shearing costs. Ewes are normally shorn once annually in early summer. However many producers are now shearing either at housing (December) or prior to joining (September). The aim of this paper is to present results from studies at Athenry on how season of shearing affects subsequent animal performance.

Shearing at housing

Shearing ewes at housing increased the weight of wool harvested by 0.3 kg/ewe relative to shearing in May. Three studies have been undertaken at Athenry which have evaluated the effects of shearing March-lambing ewes, at housing in December, on their subsequent performance and the performance of their lambs from birth until weaning.  In each of these studies ewes were housed either unshorn, or shorn and offered grass silage ad libitum. Concentrate was supplemented during late pregnancy.

The effects of shearing ewes at housing on subsequent lamb performance are presented in Table 1. Shearing at housing did not alter ewe body condition score at lambing.  Lambs born from ewes that had been shorn at housing were 0.6 kg heavier at birth and 1.9 kg heavier at weaning. Whilst shearing at housing increased lamb birth weight, it did not affect the incidence of lambing difficulty or mortality.  The increased birth weight of the lambs from ewes shorn at housing was due to increased silage dry matter intake which was partly a reflection of cold stress immediately post shearing, and more importantly, a reflection of reduced heat stress in late pregnancy and an extended gestation period. 

Table 1. Effect of shearing ewes at housing on subsequent lamb performance

 

Shearing date

 

May

Mid December

Lamb birth weight (kg)

4.1

4.7

Lamb weaning weight (kg)

31.5

33.4

The increase in lamb weight at birth (0.6 kg) was trebled (1.9 kg) at weaning at 14 weeks of age. The increase in lamb weight at weaning obtained due to shearing ewes at housing is the same response as would be expected from providing 19 kg of creep concentrate to each lamb prior to weaning, which is equivalent to a cost of approximately €6/lamb.  Shearing at housing (cost €2.50/ewe) is equivalent to a saving in creep concentrate of approximately €10/ewe for ewes rearing 1.7 lambs. Previous studies at Athenry have shown that an increase in lamb weaning weight of 2 kg reduces the age at slaughter by approximately 2 weeks.

Other advantages of shearing at housing

The recommended space allowance for unshorn ewes depends on floor type and ewe weight. For example, the recommended space allowance for ewes housed on slats and straw bedding is 1.1 and 1.2m2 for 70 kg ewes; and 1.2 and 1.4m2 for 90 kg ewes. The floor area required by shorn ewes is up to 20% less per ewe. Thus shearing ewes at housing enables more ewes to be housed in a given area.

Shearing ewes at housing occurs during a period of low labour demand for flock management and consequently spreads the annual work load more evenly. Ewes shorn at housing are easier to monitor during late pregnancy and post lambing.

Shearing at other times

Some producers opt to shear their flocks in the autumn prior to joining the ewes with rams. Two studies were undertaken to evaluate shearing either 4 weeks prior to joining (September) or at housing (December) relative to the traditional time (early summer). The results of these studies showed that shearing in autumn resulted in approximately 50% of the benefit in lamb birth weight observed when shearing was at housing. Shearing in the autumn prior to the joining period reduced fleece weight by 0.5 kg; there was no beneficial effect on litter size (a claim that is sometimes made)

Table 2. Effect of shearing ewes at housing on subsequent lamb performance

 

Shearing date

 

June

September

December

Litter size

2.0

2.1

2.0

Lamb birth weight (kg)

4.2

4.4

4.6