EFFECT OF AGE AT FIRST CALVING ON PRODUCTIVE AND REPRODUCTIVE PERFORMANCE IN A DAIRY HERD OF LOS RIOS REGION

Abstract

Productive and reproductive records since 1989 to 2007 from Punahue dairy farm of Austral University of Chile were used. The data were analyzed using SAS software; multiple linear regression statistical models were used to analyse the dependent variables: milk production, percentage of fat, percentage of protein calving interval. This was done to establish whether age at first calving was related to the independent variables. Least mean squares were obtained for each variable, and were compared using the t-test for paired terms. Age at first calving classified into four groups (22-26; 27-31; 32-37; 38-48 months).

The mean and standard deviation of age at first calving for the studied herd were 29.28±4.83 months. Most cows (68,4%) had their first calving within the age groups 1 and 2. Age at first calving had not a significant effect on protein percentage.

Least square means for the dependent variables were significantly different for milk yield, percentage of fat and calving intervaltween the groups of age at first calving.