Last update: November 24, 2010 04:06:28 PM E-mail Print

 

THE EFFECT OF NUTRITIONAL STRESS AFTER WEANING ON THE LIFETIME PRODUCTION

OF FINE AND STRONG WOOL MERINO SHEEP


W.J. Olivier1, J.J. Olivier2 & B.R. King1

 

1Grootfontein ADI, Private Bag X529, Middelburg, 5900

email: Willem olivier

2ARC:AII, Private Bag X529, Middelburg, 5900

 


During the past decades the price difference between fine and strong wool increased due to the demand for lighter weight fabrics. This increase had lead to more emphasis being placed on the production of fine wool, which lead to a tendency to produce this type of wool under less favourable feeding conditions in the extensive farming areas of South Africa. It is known that several wool quality factors such as fibre diameter, fibre length and tensile strength are influenced by the amount of available nutrients. The objective of this project was therefore to determine the influence of poor nutrition after weaning on the wool production of genetic fine wool and strong wool animals. For this project 40 fine wool (FW) and 40 strong wool (SW) lambs from the Grootfontein Merino flock were used. For the first phase of this project these FW and SW lambs were divided into two equal groups each after weaning and were kept in kraals for a period of three months. During this phase one group of each (FT and ST) received a diet with low nutritional value and the other groups received a diet with a high nutritional value (FC and SC). During the second phase of this project the animals were run in one group on natural pastures. The animals were weighed weekly during the first phase and monthly during the second phase and were shorn at the start and end of the first phase and every six months thereafter for the next 18 months. The body weight (BW1) at the end of the first phase, the body weight (BW2) at the end of the project, as well as the clean fleece weight (CFW) and the mean fibre diameter (MFD) at the end of the first phase and the project for the different groups are summarised in Table 1.

 

Table 1. The BW1, BW2, CFW and MFD at the different stages for the different groups

 

FT (a)

FC (b)

ST (c)

SC (d)

  BW1

24.59 ± 1.72b

36.46 ± 1.70a

24.15 ± 1.73d

38.23 ± 1.46c

  BW2

68.33 ± 1.91

72.09 ± 2.06

69.03 ± 1.85

74.29 ± 1.85

  End of first phase

  CFW

0.38 ± 0.07b

0.75 ± 0.07a

0.51 ± 0.07d

0.83 ± 0.06c

  MFD

15.95 ± 0.42b

16.55 ± 0.41a

18.12 ± 0.43

18.35 ± 0.35

  End of the experiment

  CFW

2.71 ± 0.14

2.81 ± 0.15

3.62 ± 0.13

3.61 ± 0.13

  MFD

20.29 ± 0.36

20.08 ± 0.39

23.32 ± 0.32

23.23 ± 0.35

The treatment groups differed (P<0.05) from those included in the superscript for a specific trait

 

It is evident that during the second phase the treatment animals showed compensatory growth, as the difference in body weight decrease from about 12kg to about 5kg. It is furthermore evident that the wool production of the fine wool animals was affected more negatively after weaning in comparison to strong wool animals. However, this negative effect was only temporary, as at the end of the experiment the FT and ST groups produced the same amount of wool as the FC and SC groups respectively.