Effect of age at first Calving and Parity Order on Lactation Length, Lactation Yield and Calving Interval in the Belgravia Dairy Farm

The obejctive of this study was to investigate the effect of age at first calving and parity order on some production and reproduction traits (lactation length, lactation yield and calving interval) in Belgravia dairy farm, which belong to the Military Corporation. The data were collected from 204 lactation records of 51crossbred cows covering the period from 2000 to 2010. The data were classified according to the age at first calving and parity number. The means for age at first calving, lactation, lactation yield and calving interval were 38.8 months, 11.20 months, 3347.9 Ib and 13 months, respectively. The statistical analysis revealed that the age at first calving had a non significant (P > 0.05) effect on all traits. The longest lactation length, obtained by the age at first calving group, ranged between 26 and 29 months, while the shortest was evident in the age at first calving group, that ranged between 41 and 45 months. The highest lactation yield was obtained for the group which had the eldest age at first calving that was 50 or more months. The lowest lactation yield and the longest calving interval were obtained for age at first calving ranged between 38 and 41 months. The shortest calving interval was obtained by the age at first calving ranged between 41 and 45 months. IX The Parity number, on the other hand, also exerted non significant (P>0.05) effects on all the traits. The longest and shortest lactation length were associated with the second and fourth parities, respectively. The highest milk yield was obtained for the fourth parity, while the lowest was obtained for first parity. Moreover, the longest calving interval was obtained by second parity and the shortes by the third parity. The effect of interaction between the age at first calving and parity number had non significant (P>0.05) effect on all traits. Howover, the longest calving interval was obtainted by the age at first calving, it ranged from 38 to 41 months in fourth parity while the shortest obtained by age at first calving and ranged from 41 to 45 months in third parity. The hightest lactation yield was obtained by the age at first calving ranging from 50 or more months at the first parity, and the lowest was obtained by the age at first calving ranged from 41 to 45 months in first parity. The shortest and longest lactations were otained by the age at first calving ranged between 46 and 49 months in parity four and 26 to 29 months in second parityrrt respectively