Factors Affecting Days Postpartum to First Service, Days Open and Pregnancy Hazard in Holstein Cows Kept under the Subtropical Conditions of Egypt

AJVS. 2021; 71(2): 45-55

Ferial M. Sahwan, Mahmoud M.A. Elmaghraby, Athanas Ngounndji, Mohammed M. Fathalla.

Abstract
The aim of this study was to investigate the possible factors affecting the number of days in milk to first breeding (DIMFB), days open (DO) and pregnancy by 400 days in milk (PREG400) in Holstein cows kept in a large herd under the subtropical conditions of Egypt. Lactation and health records of 2040 cows in a large herd covering the period between 2016 and 2017 were used. We analyzed the data using Cox proportional hazard analysis and generalized linear models. Only 38.2% of cows required less than 120 DIM to conceive, and approximately one-third of pregnancies occurred later than 200 DIM. Cows in second or higher parities recorded 5 DIMFB earlier (P Key words: DIMFB, DO, PREG400, Holstein cattle