| Titles |
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English :
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A genetic study on test-day milk yield and somatic cell count of Egyptian buffalo using random regression.
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Arabic :
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دراسة وراثية لصفتى انتاج اللبن و تعداد الخلايا الجسدية في يوم الاختبار بأستخدام الانحدار العشوائى فيي الجاموس المصرى.
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| Abstract |
Both fixed and random regressions were used to model test day records that are measured over the trajectory from days in milk (DIM) = 5 to 300 of the first three lactations for Egyptian buffalo. The covariance components were estimated with a single trait animal model with REML algorithm for each of daily milk yield (DMY) and log10 somatic cell count (LSCC) for a total of 3189 records using the random regression model (RRM). Records were taken from four buffalo experimental research herds belonging to the Animal Production Research Institute, Egypt, between 1999 and 2004. The results indicated that herd-test date (HTD) affected (P<0.001) both DMY and LSCC in all lactations. HTD increased the accuracy of the model when compared with herd-year-season (HYS) effect. DIM affected significant for DMY while it was non-significant for LSCC in the first three lactations. Age at calving had a significant effect on both DMY and LSCC in the second and third lactations. First lactation had a different trend for both DMY and LSCC when compared to the 2nd and 3rd lactations. Curves for LSCC along the trajectory of DIM in the first three lactations of Egyptian Buffalo shaped like an inverted milk production curves. Heritability estimates within each lactation for DMY and LSCC had wide ranges in all lactations. Heritability estimates for DMY and LSCC averaged 0.12, 0.22 and 0.20 and 0.15, 0.07 and 0.09 in the first three lactations, respectively. Estimates, in general, tended to increase toward edges of the trajectory. Additive genetic variance across the first three lactations for DMY had different trends at the beginning of the trajectory (low in the 1st, medium in the 2nd and high in the 3rd) and then gradually increased to the end of the trajectory. Permanent environmental variances for DMY were relatively low at early lactation and tended to increase toward the end of the trajectory. Residual variances for DMY were low at both edges of the 3rd lactation contradicting the 1st and 2nd lactations. All variances (genetic, permanent environmental and residual) were very high for LSCC in the 1st while they were low in 2nd and 3rd lactation. This result may suggest that LSCC in the 1st lactation is not genetically the same in the rest of lactations. In general, genetic parameters for SCC were comparable to those reported for dairy cattle indicating that reduction in SCC for buffaloes could be achieved using similar practices.
Key words: genetic parameters, test day, milk yield, somatic cell count, Egyptian buffalo, random regression.
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| Publication year |
2004
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| Availability location |
مكتبة معهد بحوث الانتاج الحيوانى - شارع نادى الصيد - الدقى - الجيزة
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| Availability number |
910
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| Organization Name |
Buffalo Breeding Research Department
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| Department |
Buffalo Breeding Research Department
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| Author(s) from ARC |
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| Agris Categories |
Animal husbandry
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AGROVOC
TERMS |
Buffalo milk.
Genetic parameters.
Milk yield.
Somatic cell count.
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| Publication Type |
PhD Thesis
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