Genetic evaluation for longevity of dairy cattle in the Netherlands

Abstract

Longevity of dairy cattle is an important trait from an economic and welfare perspective, as well as from a societal and government perspective. For a farmer it is beneficial to keep older cows, as it will reduce costs of rearing. The Dutch government aims to reduce the environmental impact of livestock, and for that it is also beneficial to keep older cows. Older cows produce more on average, and feed is converted more efficiently. In the Dutch-Flemish genetic evaluation of functional longevity a random regression animal model with a fifth order Legendre polynomial is used, where within-herd production level is fitted as an explanatory effect. Published breeding values for longevity are partially based on predictor traits. The breeding values for milk production, as well as udder health, claw health and locomotion are added as predictor traits through selection index theory. In this paper the impact of the introduction of genetic evaluation of longevity is assessed. Over the past 25 years all statistics on longevity metrics have been favorable. Productive life increased with 337 days to 1,445 days for cows culled in 2024. Together with a reduced amount of youngstock, the rearing period reduced 40 days to 763 days. The mean number of calvings increased by 0.8 to 3.9 calvings. Lifetime production increased in 25 years by 14,329 kg to 38,283 kg of milk (with 4.40% fat and 3.58% protein), resulting in 1,684 kg fat and 1,369 kg protein. Production per day of life increased by 4.8 kg to 17.1 kg of milk. Longevity is a result of management (e.g. feeding, housing and culling decisions), environment, and genetics. Genetically, longevity increased by 600 days, which suggests that the full genetic potential is not yet utilized. The strong increase of the genetic trend for longevity was supported by selection on udder health, claw health and feet & legs. Culling decisions can also be affected by governmental changes in regulations. The genetic trend is more consistent over the years than the phenotypic trend. Long-term trends show that all these factors together resulted in significant improvements for longevity and lifetime production. With the continuing improvement of production and health traits further improvement of longevity is expected.