Association between disease occurrence and fertility of dairy cows in three geographic regions of Chile.
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abstract
The objective was to analyze the association between disease occurrence during early lactation and reproductive performance and survival of dairy cows in high-producing herds, under different management practices in three geographic regions of Chile. Data included 30,757 lactation records of cows calving from January 2013 to June 2014 in three different locations: Central (C) area (n=6198 cows in eight herds), Central-South (CS) area(n=17,234 cows in 12 herds), and South (S) area (n=7325 cows in six herds). Data were analyzed using logistic regression and ANOVA, considering cow as the experimental unit. Covariables offered to the models included parity number, season of calving, cow and herd relative milk yield, geographic location, and management system. Average milk yield (305ME) per cow were 12,091, 11,783, and 6852kg for C, CS, and S regions, respectively. Time from calving to first service and time to conception were consistently greater for cows with at least one disease event within 50 days in milk (DIM), for cows that were reported lame, or for cows that had mastitis or metritis. The odds (95% confidence interval) of pregnancy at 150 DIM (P150) and the odds of survival until 150 DIM (S150) for cows that had at least one disease event within 50 DIM were 0.84 (0.79-0.91) times the odds of pregnancy and 0.25 (0.22-0.28) times the odds of survival for healthy cows. The odds of P150 for cows located in the C and CS areas were 1.56 (1.36-1.80) and 1.16 (1.04-1.30) times the odds of P150 for cows in the S area. The odds of S150 for cows located in the C and CS areas were 0.48 (0.37-0.62) and 0.54 (0.42-0.67) times the odds of S150 for cows in the S area. These data suggested that cow health status and geographic location are significantly associated with reproductive performance and survival in this population of Chilean dairy cows.
