Effect of seasons on days open of breeding cows

Resumen

Objective: to evaluate the effect of seasons on days open and calving date of breeding cows of the Cristo Rey cattle ranch, San Andres Tuxtla, Veracruz based on 15-years records.

Design/ Methodology/ Approach: using 15 years of production records from the Cristo Rey cattle ranch, the relationship between date of calving and next breeding was analyzed to obtain the days open (number of days defined from calving to next conception). Data used were the most recent calving date, and next breeding date. Based on calving date cows were classified into four seasonal calving groups, then the days open (calving interval) for each cow were quantified. Descriptive statistics of calving intervals were used to obtain a frequency distribution, and an analysis of variance with InfoStat^© was used to determine differences among calving intervals, also to determine if days open were associated with calving per season.

Results: a total of 985 calving events were recorded, with an overall average of 240 days open. Only 15.8% of the breeding cows had less than 103 days open. The highest percentages were counted between 104 and 358 days open. It was also recorded that 17 cows took more than a year and a half (≥ 528 days open) to breed again. With a significant difference among seasons (p = 0.0003), winter was identified as the season in which the cows that calved had the fewest days open (219).

Limitations/ Implications of the study: a correlation analysis between calving and breeding was not performed in two cycles. However, the identified trend is an approximation to the usefulness of performing such correlations as a further step.

Findings/ Conclusions: breeding and calving do not occur synchronously in the same herd. This is due not only to the calving intervals in each season, but also to other nutritional, health, and genetic factors that influence the date of breeding and calving in the same year or the following year.