TDMYTotal Dry Matter Yield
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The effect of genotypes on both TDMY (kg) and milk components such as fat (%), protein (%), lactose (%), density (kg/m3), solids-non-fat (%), total solids (%), freezing point (oC), and also pH and conductivity (uS/cm) was analyzed by repeated measurement of mixed model (SAS Proc Mixed) used from SAS program (SAS Institute 2002 Ver.
After statistically analyses, the differences between any two least squares means of the traits were compared with Least Significant Difference (LSD) for MY305 by using MSTAT-C (1989) and for TDMY and other dairy traits by using PDMIX800 (Saxton 1998).
Association analyses: The association of Pit-1 gene polymorphism with MY305, TDMY and milk components in the population was analyzed (Table 4).
According to MY305 and TDMY, cows carrying AA genotype (6390 kg +- 21.43 kg) had produce more milk compare to AB (6240 kg +- 20.72 kg) and BB (6260 kg +- 20.76 kg) genotypes.
Table 4: The association of Pit-1 gene polymorphism with MY305, TDMY and milk components.
From this database were extracted 74,023 TDMY records using the first lactations of 9,162 Girolando cows that calved from 2000 to 2011 and with age at first calving varying from 23 to 56 months.
Aiming to obtain greater data consistency, only data from cows that had their first TDMY record up to 45 days after calving or with consecutive interval between TDMY exceeding 45 days were included; cows having at least four TDMY records per lactation collected between 5 and 305 days-in-milk (DIM); and those cows with both parents known.
After data editing, remained 32,817 TDMY records from 4,056 first calving cows, belonging to six genetic groups (1/4H to 3/4G, 3/8H to 5/8G, 1/2H to 1/2G, 5/8H to 3/8G, 3/4H to 1/4G, 7/8H to 1/8G) as their racial composition of Holstein (H)-Gir (G), daughters of 276 sires collected from 118 herds between 2000 and 2011.
Distribution of the number of TDMY records and the corresponding daily milk yield over the lactation are showed in Figure 2.
When assessing the estimates of (co)variance additive genetic and permanent environmental components between the random regression coefficients it revealed that the variances of the first two coefficients of additive genetic effects were greater than the third one (Table 4), indicating that they have contributed significantly in the variation description of the TDMY records.