GENETIC PARAMETERS AND SELECTION RESPONSES OF 305-DAY AND CUMULATIVE MILK YIELD TRAITS UNDER CUMULATIVE MONTHLY RECORDING SYSTEMS IN DAIRY CATTLE | ||||
| Journal of Animal and Poultry Production | ||||
| Article 6, Volume 34, Issue 5, May 2009, Page 4541-4550 PDF (690.58 K) | ||||
| Document Type: Original Article | ||||
| DOI: 10.21608/jappmu.2009.117129 | ||||
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| Authors | ||||
| M. A. Mostafa1; A. M. Soliman2; Sheren K. Genena3 | ||||
| 1Department of Animal Production, Fac. of Agric., Mansoura Univ., Egypt. | ||||
| 2Department of Animal Production, Fac. of Agric., Zagazig Univ., Egypt. | ||||
| 3Animal Production Research Institute, Ministry of Agric., Doki, Cairo, Egypt. | ||||
| Abstract | ||||
| Lactation records used in the present study were of Fleckvieh cows, calveing in two successive years (1990 and 1991), from the official Federation of Austrian Cattle Breeders (ZAR). Normal 305-day milk yield (305-day MYT) records and calculated cumulative milk yield traits (CMYT) of each of three periods were used. First cumulative 31-120 day (CMRS1), 2nd cumulative 61–150 day (CMRS2) and 3rd cumulative 31–150 day (CMRS3) represent the milk records of 1st lactation only. Monthly test-day records were computed and used for genetic evaluation. Available data consisted of 19000, 27158 and 18999 lactation records of daughters sired by 1424, 1748 and 1424 for CMRS1, CMRS2 and CMRS3, respectively. Yields of 305-day and calculated cumulative milk – (MY & CMY), fat – (FY & CFY), protein – (PY & CPY), fat – plus – protein – (FPY & CFPY) and protein/fat ratio – (PY/FY% & CPY/FY%) were studied in CMRS1 to CMRS3. Estimates of heritability (h2) for CMYT under different cumulative milk recording system CMRS ranged from 0.32 to 0.43, while for 305-day MYT h2 ranged from 0.48 to 0.59. However, estimates of coefficients of additive genetic variation (CAGV%) for CMYT under different CMRS ranged from 6.2 to 7.5%, while for 305-day MYT, CAGV% ranged from 6.2 to 7.7%. Generally, the highest estimates of h2 and CAGV% on CMYT were found under CMRS2. However, the estimates of h2 for cumulative fat yield (CFY) and percentage of protein yield/fat yield – (CPOF%) under CMRS were higher than those for all studied CMYT. Estimates of genetic correlation (rG), phenotypic correlation (rP) and environmental correlation (rE) between 305-day MYT and CMYT under different CMRS were generally positive, varying from moderate to high. Selection for CMYT under the CMRS2 had the highest correlated response in relation to 305-day MYT. Therefore, these results suggest that, attempts to increase CMYT by selection would increase 305-day MYT nearly as much as direct selection. | ||||
| Keywords | ||||
| Fleckvieh; cumulative milk recording system; genetic parameters; selection response; 305-day milk yield traits; cumulative milk yield traits | ||||
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