Effect of age at first calving and first lactation milk yield on productive life traits of Syrian Shami cows

الملخص EN

The objective of this research was to study the effect of age at first calving (AFC) and first lactation milk yield (FMY) on productive life traits of Syrian Shami cows.

In this study, the complete records from birth to voluntary culling were collected on 605 cows during the period from 1981 to 2010 at Deir al-Hajar station in Syria.

Data were analysed using the General Linear Model (XLSTATE, 2019).

The least squares means fo r AFC and FMY were 30.9±0.16 months and 1203±34 kg, respectively.

The optimum AFC was ≤ 25 months to achieve the maximum lifetime milk yield, productive life and number of calvings.

Increasing AFC (especially over 31.8 months) decreased lifetime milk production, lifetime daily milk yield, productive life and the number of lactations.

First lactation milk yield reflected the production capacity in subsequent lactations.

The first calvers of more than 1900 kg produced high milk yield during their life and had shorten dry periods.

While cows that produced less than 600 kg milk in the first lactation had the lowest life time milk production.