GENETIC EVALUATION FOR MILK PRODUCTION, REPRODUCTION TRAITS AND PERSISTENCY OF LACTATION USING SINGLE- AND TWO-TRAIT ANIMAL MODEL ANALYSES FOR FRIESIAN COWS IN COMMERCIAL HERDS IN EGYPT | ||||
| Journal of Animal and Poultry Production | ||||
| Article 8, Volume 30, Issue 7, July 2005, Page 3637-3653 PDF (2.37 MB) | ||||
| Document Type: Original Article | ||||
| DOI: 10.21608/jappmu.2005.238026 | ||||
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| Author | ||||
| N. A. Shalaby, | ||||
| Animal Production Department, Faculty of Agriculture, Mansoura University, EI-Mansoura, Egypt. | ||||
| Abstract | ||||
| A total of 1293 normal first lactation records 01 Holstein Friesian cows were collected from two commercial dairy herds during the period from 2000 to 2003. Genetic parameters and breeding values for productive. reproductive traits and persistency of lactation were analyzed by using single·trait and two-trait animal model analyses of each reproduction, persistency and age at first calving traits jointly with milk yield. Traits studied were total milk yield (TMY. kg). 305·day milk yield (305-d MY, kg). 70-day milk yield (70-d MY, kg). days in milk (DIM, days), calving interval (CI, day). the days open (DO, day), age at first calving (AFC, month) and persistency of milk yield (Per MY). Spearman rank correlations between EBVs for traits studied from single-trait and two-trait analysis with milk yield were estimated. Unadjusted means of AFC. DO, CI. Per MY, DIM, 70-d MY. 305-d MY and TMY were 27.7 month. 162.7. 430.2 days. 0.822 unit. 353.9 days, 1870. 5546 and 6733 kg. respectively. Therefore. the Holstein dairy farming system can show high production performances under adequate management with lower reproductive efficiency under production system of commercial herds in Egypt. Estimates of heritability of AFC, DO. Ct. Per MY, DIM, 70-d MY. 305-d MY and TMY were 0.19tO.07S. 0.11 ±0.064, O.12±O.066, O.08±0.OS2. 0.27±O.091 O.32±0.105, 0.34±0.107 and 0.28±0.139, respectively. using single-trait analysis. Some minor differences were observed in heritabilities obtained from single versus two-trait genetic. The genetic and phenotypic correlations between mitk yield traits (TMY, 305- d MY and 70-d My) and fertility traits (CI and DO) showed to be medium to high positive (undesirable) of Holstein Friesian cows under the commercial herds in Egypt. The phenotypic correlations between age at first calving and each of DO and Ct were negative (-0.19 and -0.35, respectively), however, the genetic correlations between the same traits were positive (0. 74±0.1 9 and 0.85±0.18, respectively). The phenotypic correlation between age at first calving and persistency of lactation was negative and close to z.ero (-0.07), however, the genetic correlation between the same traits was positive (0.12tO.20). The range of breeding values obtained from single-trait analysis of all pedigree animals for AFC. DO and CI were 5.02 month, 99.71 and 105.38 days, respectively. White, the range of sire breeding values were 4.86 month. 61.59 and 106.46 days, respectively. The percentage of number of sires (animals) which had negative breeding value estimates (EBVs %) for reproductive traits and persistency of lactation ranked differently between the two analyses. Higher standard deviations of breeding values were obtained for two-trait than singte-trait analyses. indicated the existence of more genetic variation among sires (animals) and hence increase the possibility of sire selection for daughter fertility. Lower correlations (diHered from unity) between breeding values estimated by singte-trait and the others by two-trait analysis | ||||
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