Extension Dairy Scientist, Genetics & Management
(540) 231-4762; email@example.com
Genetic evaluations are available for calving ease and incidence of stillbirths in Holstein and Brown Swiss sires. The proofs come in two forms: one which evaluates the bull himself as the sire of the calf (sire calving ease, SCE, or sire stillbirth rate, SSB) and one which evaluates the ease with which a bull’s daughters give birth (daughter calving ease, DCE, or stillbirth rate of daughters, DSB). Collectively, these four proofs influence the healthy birth of replacements from healthy dams.
Calving ease proofs in Holsteins range from 3 to 17, with well over 200 active AI Holstein sires available at 7% difficult births or less. Ranges of proofs for Brown Swiss are smaller, as is the range in stillbirth proofs for both breeds.
Dairy producers everywhere recognize the importance of using bulls with lower calving ease proofs on virgin heifers, but what about older cows? Bulls that produce the higher rates of difficult births will transmit genes for difficult calving to their daughters, regardless of the age of the mother. When bulls with high SCE are used on older cows, chances are good that heifer calves will be born easily enough, but they will inherit difficult calving genes from their sire that they in turn pass on to their calves.
Proofs for stillbirth rates are very new to producers, and questions about their importance are only natural. Stillborn calves are an economic loss. Producers can use Holstein bulls in active AI service with sire stillbirth proofs less than 6% and over 11%. A 5% difference between two bulls in stillbirth rates is extreme, but even 1 and 2% differences affect the budget of a dairy farm. Proofs for SSB or DSB of 10 or more are extreme in the wrong direction. There are plenty of proven Holstein bulls available to pass on these outliers.
Factoring the economic value of calving ability in with production, productive life, and other fitness traits for which genetic evaluations also exist is a job for an economic index. Net Merit does the job well, and should be an important guide when choosing which bulls to use in commercial dairy herds.