In this study the possibility of body size estimation of new born lambs using image processing and its effect on the genetic gain of a simulated population has been investigated. The body size of 158 new born lambs of Zandi sheep was evaluated via appraisal method, digital image processing and metric methods. The correlation coefficients between metric lamb size with quantities were calculated from image processing method and appraisal method were 0.88 and 0.48, respectively (P < 0.01). In the next step, two populations were randomly simulated using R2.15 programming environment, and two different scenarios based on two lamb size measurement methods were studied. In the first scenario, it was assumed that the animal body size is determined using image processing technique in continuous values, while in the second scenario it was assumed that the body size is determined via appraisal method in discrete values. As results, the accuracies of breeding value estimations in the first and second scenario were 0.89 and 0.78, and the genetic trends were 0.46 and 0.28, respectively (P < 0.01). The results showed that determination of lamb size based on proposed image processing method is feasible, and replacement of this new method instead of human appraisal method could increase the genetic gain in the breeding herds.
In this study, the data of body weights and pelt records of Zandi sheep kept at the Khojir national park breeding station of Iran were used to estimate phenotypic, genetic and environmental trends for birth weight (BW), 3 months weight (3MW), 6 months weight (6MW), yearling weight (YW), curl type (CT), pattern score (PS) and Luster (Lu) of pelt. Data were analyzed for each trait using derivative-free REML procedures under a univariate animal model. Genetic, phenotypic and environmental trends were estimated by regression of the estimated mean of breeding values, phenotypic mean and difference between estimated mean of breeding values and phenotypic mean on birth year, respectively. The average additive direct genetic trends for BW, 3MW, 6MW, YW were 0.00190.001, 0.03490.004, 0.02890.007 and 0.02490.004 g/year and for CT, PS and Lu were 0.0069.002, 0.00190.002 and 0.00290.004, respectively. Although selection for body weight traits was effective and significant genetic improvements were obtained, limited genetic improvement in the pelt traits were detected.
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