Last update: November 22, 2010 12:16:31 PM E-mail Print

 

Production and reproduction of adult ewes of the Cradock Fine Wool Merino Stud

 

W. J. Olivier 1*, M. A. Snyman1, J. J. Olivier2 & A.C. Greyling3


 1Grootfontein Agricultural Development Institute, Private Bag X529, Middelburg, EC, 5900, South Africa

2 Agricultural Research Council: Animal Improvement Institute, Private Bag X5013, Stellenbosch, 7599, South Africa

3 Cradock Experimental Station, PO Box 284, Cradock, 5880, South Africa

E-mail: Willem Olivier

 


The Cradock Fine Wool Merino Stud was established in 1988 on a request from the wool industry. Ewes were bought from Merino farmers with the finest clips throughout South Africa and four rams were imported from Australia. The purpose of this paper was to estimate the genetic parameters for the reproductive performance of the ewe flock and the genetic and phenotypic correlations among the reproductive and 15-month old production traits, as well as to calculate least squares means (LSM) for the ewe flocks wool production traits. Data collected from 1189 ewes born within this stud from 1988 to 2000 were used for this analysis. The reproduction traits analyzed included total number of lambs born (NLB) and weaned (NLW) and the total weight of Iamb weaned (TWW). The number of lambing opportunities and year of birth of the ewe were included as fixed effects for all three these traits. Only records from ewes (n=2689), born within this stud, that were three years and older were used for the calculation of the LSM for body weight (BW), clean fleece weight (CFW), mean fibre diameter (MFD) and staple length (STPL). Several fixed effects were tested for significance. Effects which had a significant effect (P<0.0I) for a specific trait are indicated in brackets: year (BW, CFW, MFD, STPL), year of birth of the ewe (BW, CFW, MFD, STPL), line (CFW, MFD, STPL) and the number of lambs weaned during the previous lambing season (BW, CFW). The respective LSM and the standard errors for BW, CFW, MFD and ISTPL were 72.15 ± 6.52 kg, 4.35 ± 0.76 kg, 20.09 ± 1.15 μm and 94.64 ± 9.98 mm. The LSM for NLB, NLW and TWW were 4.43 ± 1.61, 3.67 ± 1.15 and 92.70 ± 36.00 kg respectively. The direct heritability (on the diagonal) of NLB, NLW and TWW and the genetic (above the diagonal) and phenotypic correlations (below the diagonal) among these traits, as well as the correlations among these traits and the 15-month old production traits are presented in Table I.

 

 

The genetic correlations obtained between BW and NLB, NLW and TWW are much lower than corresponding estimates found in the literature. These unfavourable correlations can possibly be ascribed to the fact that these ewes are kept under optimum feeding conditions. Their BW could therefore be at the plato or downward trend according to the Sewall-Wright body weight reproduction relationship.