Improvement through selection for milk in a closed flock of Beetal goats
Data on 1436 Beetal nannies, progeny of 103 sires, and spread over 37 years were analyzed to obtain phenotypic and genetic parameters of age at first kidding (AFK), first lactation milk yield (FLY), first lactation length (FLL) and first kidding interval (FKI) and lifetime production combining first three lactations (LTP), independent of the effect of year and season of kidding. For these traits least square means were 776 days, 130.1 kg, 174 days, 382 days and 559 kg and heritability estimates were 0.15, 0.29, 0.04, 0.13 and 0.30, respectively. Genetically, LTP had large and negative correlations with AFK, FLL and FKI and a large positive correlation with FLY. Phenotypically the correlations of LTP were positive but extremely low with AFK, large and positive with FLY and FLL and negative and extremely low with FKI. Selection indices combining AFK, FLY, FLL and FKI to maximise genetic gains in LTP were constructed. Although the index incorporating all the four traits had the maximum correlation (R equal 0.69) with breeding values for LTP and will bring maximum genetic gain ( GLTP equal 29 kg), the index (I equal 0.39 FLY - 0.22 FLL - 0.09 FKI) will be only slightly less efficient (R equal 0.65 and GLTP equal 27 kg) and is recommended
| Main Authors: | , , , |
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| Format: | Texto biblioteca |
| Language: | eng |
| Published: |
Scottsdale, AZ (EUA)
1982
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