Early-life cow-level risk factors for sole ulcers in primiparous dairy cows.

Sole ulcers negatively affect cow welfare and production economy. Previous cases of sole ulcers increase the risk of new or recurrent cases, and prevention of sole ulcers during the first lactation may therefore have a long-term effect, also in later lactations. Until now, risk factors for sole ulcers in the first lactation, associated with the period before heifers calve for the first time, have not been investigated. This study evaluated early-life cow-level risk factors for sole ulcers at the first hoof trimming in the first lactation. Early-life risk factors were defined as risk factors associated with the period before a cow calves for the first time. A dataset including information about all hoof trimming recordings during the years 2020 to 2022, and information about individual cows, was retrieved from the Danish Cattle Database. The dataset included only primiparous cows, and only cows that were hoof trimmed at least once during the first lactation. Overall, 1.95% of 466,113 cows included in the study had sole ulcers at the first hoof trimming in the first lactation. Results from a logistic regression model demonstrated a statistically significant interaction between breed and age at first calving (grouped based on quartiles within breed). Overall, across breeds, odds ratios of sole ulcers at the first hoof trimming in the first lactation were generally approximately 0.5 in the first quartile of age at first calving, approximately 0.6 in the second quartile, and approximately 0.75 in the third quartile, compared with the fourth quartile within the same breed. Odds of sole ulcers were generally higher in Jersey and Danish Red Dairy cows, compared with Holstein. In conclusion, the odds of sole ulcers in the first lactation increased with increasing age at first calving, and was approximately twice as high in cows calving among the oldest 25% within a breed, compared with cows calving among the youngest 25%. Focus on early-life risk factors for sole ulcers may have a major influence on the occurrence of sole ulcers throughout the life of cows.