Effect of sire, age at first calving, season and year of calving and parity on reproductive performance of friesian cows under semiarid conditions in egypt [electronic resource]

Includes reference.

The objective of this paper was to study some factors affecting reproductive performance of a locally-born Friesian herd in Egypt. Data of 2096 reproductive records representing 482 Friesian cows daughters of 38 sires raised at the Dairy Unit of Milk and Meat Project of Faculty of Agriculture, Alexandria University, Egypt (located at the northern western part of the Nile Delta) between 1985-2002 were utilized to study the effects of sire of the cow, age at first calving (AFC), season and year of calving/birth and parity on period from parturition to first service (FSP), days open (DO), calving interval (CI), number of services per conception (NSC), AFC and breeding efficiency (BE). The least squares mixed model analysis by SAS (1999) indicated that the overall least squares means (± standard error) of FSP, DO, cl, NSC, AFC and BE were 88.4 ± 1.1, 130.7 ± 1.9, 403.1 ± 1.9 days, 2.1 ± 0.1 services, 30.7 ± 0.1 months and 90.1 ± 0.6 %, respectively. Sire had highly significant (P<0.01) effect on DO, CI, NSC and AFC, but had insignificant effect on FSP and BE. The influence of AFC on FSP was highly significant (P<0.01) and not significant on DO cl, NSC and BE. Cows had AFC more than 36 months had the longest FSP (92.6±4.5) and cows had AFC less than 29 months of age had 87.8±2.7 days FSP. Season of calving had significant effect on FSP (P<0.01), DO and CI (P<0.05), but had insignificant effect on NSC. Season of birth had no significant effect on both AFC and BE. Cows calving in autumn had the shortest CI (394.3±4.7 days) comparing with those calved in other seasons (ranged between 404.8±6.5 and 409.4±5.2 days). Cows calving in autumn also had the shortest DO (122.6±4.8 days). Year of calVing/birth had significant (P<0.05 or P<0.01) effect on all traits studied. A decreasing efficiency in reproductive performance of cows was observed over time. The shortest FSP and DO were in the period 1988 to 1990 (64.3±5.3 and 98.1±8.9 days, respectively) and the longest were in the period 2000 to 2002 (107.5±5.2 and 188.1±8.8 days, respectively). Calving interval increased from 371 days in 1988-1990 to 450 days in 2000-2002. NSC increased during 1985-1990 from 1.7 services to 2.3 during the period 1991 to 1999. Breeding efficiency deteriorated from 96.7% in 1982-1984 to 84.8% in 1994-1996 and AFC increased from 30.8 to 33.8 months during the same periods. Parity had highly significant effect (P<0.01) on FSP, DO and CI and had insignificant effect on NSC. Generally, FSP, DO and CI decreased with increasing parity. The results of the present study showed that sire of the cow, managerial systems and appropriate environmental conditions have significantly effects on reproductive efficiency of Friesian cows of the herd under investigation. The highly significant (P<0.01) effect of sire on DO, CI, NSC and AFC indicating that sire selection may be used as a useful tool for the genetic improvement of these reproductive traits

Summary in Arabic.

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