Season of conception is associated with future survival, fertility, and milk yield of Holstein cows.

摘要: ABSTRACT Environmental influences during different stages of pregnancy can induce lifelong changes in the structure, physiology, and metabolism offspring. Our hypothesis was that season conception (when offspring conceived), associated with heat stress conditions at initial embryonic development, affects lifetime performance survival female after birth. The objective to analyze association between month subsequent survival, fertility, milk yield cows maintained on dairy farms Florida, where climate summer is hot humid but winters are mild. Initial data consisted 667,104 Dairy Herd Improvement lactation records from calving 2000 2012 152 herds. Dates were estimated as birth date minus 280 d. magnitude each herd quantified by comparing winter. Wood's curves fitted adjust yields for effects days milk, residuals obtained calendar month. A sine function 12 per farm. difference highest lowest points termed seasonality index, a measure direct effect production. Herds categorized 3 levels [low (seasonality index values less than 25th percentile value; 5.22)]. Cows grouped their conception: (July–September) winter (December–February), comparisons performed parity using logistic regression, ANOVA, analysis. Two models developed. Model included complete population (n = 337,529 records) conceived or summer. B 228,257 had parent-average genetic information available be able correct farmer's use lower merit sires Other variables year calving, age first herd. Models run group (1, 2, ≥3). In both models, versus odds (95% confidence interval) second 1.21 1.15 times B, respectively. Numbers breeding consistently smaller months across all categories. Milk (305 d 70 milk) greater conclusion, better There evidence may have consequences