Abstract

Introduction. The young calf rearing method, determines the dairy cow of the future. Therefore, health, feeding and housing techniques, influence the start and performance of the productive life of a dairy cow. Objective. The aim of this work was to determine the effect of animal and environmental factors, modifiable and non-modifiable on the first lactation milk yield (FLM) in specialized dairy farms from Costa Rica. Materials and methods. A cohort retrospective study was conducted. A total of 2747 Jersey and Holstein cows, with age at first calving (AFC) between the years 2013 and 2015, belonging to twenty-two specialized dairy herds located in different ecological zones of Costa Rica, with data in the Bovine VAMPP program, were included in the study. All data in the present research was analyzed by descriptive analysis and a generalized linear model. Results. The average FLM at 305 days was 5485.8 kg (±1547.8). Non-modifiable variables, like breed, had significant effects over FLM, with 5360.1 kg (CI95%: 5158.2-5562.1) and 4694.1 (CI95%: 4578.5-4809.7; P<0.001) for Holstein and Jersey breeds respectively. AFC, had a significant effect over FLM, were a tendency to increased milk production with higher AFC was found until twenty-six month of AFC, after that milk yield remain stable (P<0.001). Furthermore, the results showed a significant effect of management as a modifiable variable (P<0.0001) revealing that farms with high quality calf rearing protocols produced 213.9 kg (FML: 5809.0; CI95%: 5570.6-6047.7) more milk in their first lactation than heifers raised under medium quality rearing and 1133.7 kg more milk than animals from low quality rearing programs (FML: 4676.3; CI95%: 4158.3-5194.3). Conclusion.These results show that rearing factors affect the productive life time of dairy cows in tropical operations. Tropical environmental conditions, including temperature, humidity and precipitation, significantly affect the productive behavior of dairy cows.