Age at first calving and productive, reproductive and longevity indicators of Holstein x Jersey dairy cows

Abstract

Breeding replacement heifers represents a major challenge and investment for dairy farmers. The objective of the work was to evaluate the effect of age at first calving on productive, reproductive and longevity indicators in grazing Holstein x Jersey dairy cows. Retrospective data from 1549 primiparous Holstein x Jersey cows were used between January 1, 2006 and December 31, 2021 from a commercial establishment, located in the central-west of the province of Entre Rios, Argentina. The animals were divided into three categories discriminated by their age at first birth (EPP): Group 1 (G1): EPP < 24 months, Group 2 (G2): EPP between 24,1 and 30 months, and Group 3 (G3): EPP > 30,1 months. The variables EPP, milk production (PL305), calving interval (IPP), fertility index (IF) and parity number (NP) were analyzed. The highest number of cows (P < 0.05) occurred in G2: 54%, then by G1: 37% and finally G3: 9%. The results showed that the categorization carried out made it possible to define three different EPPs and that these groups had similar behaviors (P > 0.05) for the variables PL305, IPP and IF. For the NP, significant differences were found (P < 0.05) showing a greater number of births for the G1 group. It was concluded that under the conditions analyzed and Holstein x Jersey cows, it is feasible and favorable to reduce the age at first birth below 24 months, without affecting productive, reproductive and longevity performance.