Genetic analysis of productive life length in Holstein dairy cows using Weibull proportional risk model

Abstract

Abstract. In recent decades, there has been a downward trend in length of productive life (LPL) in Holstein cows across industrial dairy herds. This study examined the factors that might influence LPL and estimated the genetic parameters of LPL in Holstein dairy herds in Isfahan province, Iran. LPL is defined as the number of days between the first calving and the end of recording. Data consisted of 35 137 records of productive life from registered cows that started first calving between 1991 and 2012. Cows that remained alive at the end of the study were considered right-censored. The average lifetime for culled and censored cows was 938 and 1003 days, respectively. A survival analysis was applied using a proportional risk model with a Weibull distribution. Milk production was divided into five groups, where the culling risk of cows with a milk yield of less than 1.5 standard deviations (SD) of the mean was 3.5 times greater than the culling risk of high-producing cows producing more than 1.5 SD above the mean. Results showed that culling risk increased almost linearly beyond the milk production groups. Furthermore, somatic cell count and age at first calving significantly increased the culling risk across the herds. The results for the combined effect of parity × stage of lactation showed a decrease in culling risk during the first calving, and an increase during the further parities. Moreover, a higher age at first calving was observed, reflecting a lower risk of culling. Estimated heritability were 0.074 and 0.18 based on a logarithmic scale and original scale, respectively. According to the results, use of Weibull models showed that the proportional culling risk was higher in low-production cows, but a higher risk ratio was revealed in high-milk-production cows. However, there were some fluctuations in genetic trends, but an overall increase was observed in LPL which will lead to a longer LPL of Holstein cows in Isfahan province.

Analysis of Longevity Traits in Holstein Cattle: A Review

“…The natural lifespan of cows is approximately 20 years, but the average culled time is much earlier than the natural life. Moreover, cows will be eliminated if they cannot reach the peak production to obtain the highest profit (Najafabadi et al, 2016).…”

comparative study between Shami and Holstein cows for longevity and productive lifetime traits under subtropical conditions

“…The longevity traits of cattle are defined as the time from its birth date to the culling date (Dallago et al, 2021). The natural lifespan of cattle may reach 20 years, but they were culled as much earlier than their expected life, due to their low milk production (Najafabadi et al, 2016). Whereas, the actual productive life of dairy cattle ranges between 3 to 4.5 years (El Sabry and Almasri, 2022), moreover, the highest milk yield and related outcomes happen at the fifth and sixth parity (Horn et al, 2012).…”

Combinations of Linear Type Traits Affecting the Longevity in Hungarian Holstein-Friesian Cows

“…Longer productive life increases the profits and decreases the heifer replacement costs [ 2 ], as well as decreasing the methane emission per kg of milk produced [ 3 ], thus reducing the environmental footprint of the milk industry [ 4 ]. According to [ 5 ], the production life was less than 3–4.5 years, whereas the natural lifespan was approximately 20 years to [ 6 ]. The average number of lactations ranges from 2.1 to 2.2 in the Hungarian Holstein-Friesian population.…”