RELATIONSHIP BETWEEN MILKING FLOW RATE AND MILK SOMATIC CELL SCORE IN HOLSTEIN FRIESIAN COWS USING RANDOM REGRESSION ANALYSIS

2006 Egyptian Journal of Animal Production  
Random regression co-variance components of test-day milk somatic cell score (Mk SCS ) and milking flow rate (Mk FR ) were estimated. Data consisted of 232,570 testday observations from 3864 cows daughters of 3012 dams and 361 sires in 1 st lactation recorded between 1998 and 2001 of 73 dairy herds. Multiple-trait random regression animal model used included random animal additive genetic, random permanent environment effects by lactation and days in milk. Estimates of heritabilities of Mk SCS
more » ... nd Mk FR were around of 0.21 and 0.32, respectively. Additive genetic correlations between early measures of both traits were high and positive. However additive genetic correlations between early and late measures were negative. Permanent environmental correlations were all positive in and showed the lowest differences among estimates than the other correlations. The lowest genetic estimates were obtained during the first 90 to 150 days in milk. Milking flow rate showed the highest estimate of heritability near to lactation end and the highest permanent environmental effect near mid-lactation. Genetic correlations between Mk FR and Mk SCS at the same DIM were negative and ranged from -0.49 to -0.98. These results indicated that faster milking cows genetically tend to produce higher quality milk with lower somatic cell concentration. The magnitude of permanent environmental correlations between both traits increased with progressing lactation till the 240 days in milk (-0.57 to -0.80) and then slightly reduced to -0.74 at the end of trajectory. Additive genetic correlations between early measures of Mk FR with late measures of Mk SCS were considerably high and positive (reaching 0.64). Additive variances in both traits differed significantly, indicating that trait observations during different stages of lactation should not be considered as repeated observations of the same trait. Also current results suggest that achieving goals of genetic selection for improving milk flow rate and reduced milk somatic cell is possible during early lactation months.
doi:10.21608/ejap.2006.103935 fatcat:d6nm5jqrxfdnbdx4iqhb2kgdqe