- Are ram buyers making use of performance data when buying rams at the Grootfontein official ram sale?
|Last update: January 17, 2011 02:09:04 PM|
ARE RAM BUYERS MAKING USE OF PERFORMANCE DATA WHEN BUYING RAMS AT THE GROOTFONTEIN OFFICIAL RAM SALE?
M.A. Snyman & M.J. Herselman
Grootfontein ADI, Private Bag X529, Middelburg (E.C.), 5900, South Africa
Much effort is put in by various institutions, to inform and educate breeders and ram buyers in the use of performance testing data and BLUP of breeding values (EBV's) in their selection programmes. It is, however, not easy to determine if this education is successful and whether ram buyers actually take these information into consideration when buying rams on official ram sales. In an effort to obtain more information in this regard, data from the annual Grootfontein ram sale were analysed.
MATERIAL AND METHODS
Performance testing data, EBV's and sales prices for eight ram sales (from 1990 to 1997) were obtained from the respective GADI sales catalogues. Data on Afrino rams (n=98), Grootfontein Merino stud rams (n=95) and fine wool merino rams (n=107) were analysed by means of PROC REG-procedures of SAS (Littell et al., 1991). Possible price determining factors included for Afrino sheep were weaning weight index (WW -I) and EBV (WW-EBV), 16 month body weight index (BW-I) and EBV (BW-EBV), clean fleece weight index (CFW-I) and EBV (CFW-EBV), fibre diameter index (FD-I) and EBV (FD-EBV), birth status (BST) and year. The same traits were included for the Merino rams, except for pleat score index (PS-I) and EBV (PS-EBV) which were included instead of WW-I and WW-EBV.
Firstly, stepwise regression analyses were done on the entire data sets for each group. Secondly, to determine if there were any change in the price determining factors over the years, the data were analysed with stepwise procedures for four two-year interval periods (1990-1991. 1992-1993, 1994-1995 and 1996-1997). Thirdly, overall merit was calculated for each ram as follows:
(3xBW)+(2xCFW)-(2xFD) for Afrino rams, and
(1xBW)+(5xCFW)-(7xFD)-(1xPS) for Merino rams.
The influence of overall merit on price was determined for the four two-year interval periods.
RESULTS AND DISCUSSION
Stepwise regression analysis on the Afrino data indicated that BW-EBV (b=84.1; R2=0.13), WW-I (b=26.2; R2=0.07) and CFW-I (b=16.0; R2=O..07) were the most important factors determining sales price of Afrino rams. For Grootfontein Merino rams, BST (b = -1722; R2=0.11), FD-EBV (b= -1115; R2=0.0.09), BW-1 (b=53.71; R2=0.03) and year (b=176.9; R2=0.02) contributed significantly to sales price. Year (b=394.8; R2=0.16), CFW-I (b=50.3; R2=0.04) and FD-EBV (b= -1742; R2=0.04) were the most important factors determining sales price of fine wool Merino rams.
The results obtained from stepwise regression analysis for the four two-year interval periods are summarized in Tables 1, 2 and 3 for Afrino, Merino and fine wool Merino rams, respectively. From these Tables it is evident that there was no trend over the years for any of the groups in terms of these price determining factors.
From these results it is evident that ram buyers do not place much emphasis on performance testing data or EBV's when buying rams on official ram sales where such information is available.
Littell, R.C. et al., 1991. SAS-system for linear models, 3rd Ed. SAS Institute. Inc. Cary,