Genetic study of fertility traits and productive in a local born Friesian cattle in Egypt
1999
Khattab, A.S. (Tanta Univ. (Egypt). Dept. of Animal Production) | Atil, H.
A total 1481 first lactation records of local born Friesian heifers were collected from Sakha Farm, Animal Production Research Institute, Ministry of Agriculture, during the period from 1980 to 1993. A linear mixed model was used to study the fixed effects of month and year of calving, age at first calving as a covariate and the random effect of sire on productive traits (i.e., 90 day milk yield (90dMY), 305 day milk yield (305dMY), total milk yield (TMY), lactation period (LP) and dry period (DP)). The effects of the same factors on reproductive traits (i.e., days open (DO) and calving interval (CI)) were also studied. Least squares means of 90dMY, 305dMY, TMY, LP, DP, DO and CI were 959kg, 3252kg, 3709kg, 367d, 65d, 145d and 426d, respectively. A least squares analysis of variance showed significant effect of month of calving on 90dMY, 305dMY, TMY and LP (P0.05 or P0.01). Year of calving had a significant effect on all traits studied (P0.05 or P 0.01). Including age at first calving (AFC) as a polynomial regression of the second degree in the model yielded significant (P0.05 or P0.01) partial linear regression coefficients of 90 dMY, 305dMY, TMY arid DP on AFC while the quadratic term was significantly only for 305dMY. Sire of the heifers had a significant effect on all productive traits. Heritability estimates for 90dMY, 305dMY, TMY, LP, DP, DO and CI were 0.30 plus minus 0.08, 0.30 plus minus 0.08, 0.15 plus minus 0.06, 0.10 plus minus 0.06, 0.09 plus minus 0.06, 0.05 plus minus 0.06, 0.05 plus minus 0.06, respectively. In addition, genetic and phenotypic correlation between different traits studied are calculated and tabulated. Negative genetic correlation between each of DP, DO and CI and 90dMY, 305dMY and TMY concluded that selection against dry period and days open will increase milk yield. Therefore, a reduction of DP and DO are the desirable goal of dairymen.
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