Relationship between somatic cell score and longevity of Holstein cows in Brazil using a piecewise Weibull proportional-hazard model

2019 ◽  
Vol 59 (8) ◽  
pp. 1546
Author(s):  
Elisandra Lurdes Kern ◽  
Jaime Araujo Cobuci ◽  
José Braccini Neto ◽  
Darlene dos Santos Daltro

The objective of the present work was to evaluate the effect of somatic cell score on the longevity of Holstein cows raised all over Brazil, using a piecewise Weibull proportional-hazard model. The following two longevity traits were defined: true longevity, number of days from first calving to culling; and functional longevity, approximated by correcting true longevity to within-herd-year production. Records on productive life of 131330 cows were used. The model included the time-independent effect of age at first calving. The other effects were time-dependent, and included the following: region by year of calving, variation in herd-size class, milk-production class by year of calving within herd, within-herd milk-production class by number of lactations, within-herd fat content, within-herd protein content, and somatic cell score (SCS). The overall mean of the somatic cell counts (SCC) was 322000 cells/mL. The highest SCC mean was found between 130 to 290 days of lactation. The SCC mean decreased over the years. Cows from Region 5 (Rio Grande do Sul) showed higher SCC means. The risk of culling was slightly higher for functional longevity than for true longevity. The impact of longevity was high in cows from first to fourth lactation with a high SCS, with the risk of culling varying from 0.90 (true longevity: second lactation and Class 2) to 1.2 (functional longevity: fourth lactation and Class 5). Cows at the fifth lactation with a lower SCS had a higher risk of culling (1.4). Including the effect of SCS class by stage of lactation in the models was not beneficial. The decrease in SCS, especially from the first to fourth lactation, can be used for indirect selection to improve the longevity of Holstein cows in Brazil.

2008 ◽  
Vol 53 (No. 3) ◽  
pp. 91-97 ◽  
Author(s):  
G. Mészáros ◽  
J. Wolf ◽  
O. Kadlečík

A proportional hazard model was used to analyze the impact of the most important factors on the length of productive life in 44 796 Slovak Pinzgau cows. The calculations were carried out with Survival Kit 3.12. The milk production level within a herd was the most important factor. The relation between the milk production level and the culling risk was strongly non-linear. Cows with extremely low milk production (less than 1.5 standard deviations below average) had a 4.8 times higher culling risk than average cows. The culling risk for the highest yielding cows was about one half of the risk of average cows. In the first lactation the culling risk was highest at the beginning and decreased in the course of lactation whereas in subsequent lactations the culling risk was highest at the end of lactation. The risk decreased with parity. The effect of age at first calving did not have a large influence on the length of productive life, although a linear increase in culling risk was observed as the age at first calving increased. Cows from expanding herds were at lower risk to be culled compared to cows in herds of stable and decreasing size.


2016 ◽  
Vol 185 ◽  
pp. 89-96 ◽  
Author(s):  
Elisandra Lurdes Kern ◽  
Jaime Araujo Cobuci ◽  
Claudio Napolis Costa ◽  
Vincent Ducrocq

2018 ◽  
Vol 75 (6) ◽  
pp. 470-478 ◽  
Author(s):  
Elisandra Lurdes Kern ◽  
Jaime Araujo Cobuci ◽  
Cláudio Napolis Costa ◽  
Vincent Ducrocq

2011 ◽  
Vol 83 (2) ◽  
pp. 95-102 ◽  
Author(s):  
Osamu SASAKI ◽  
Mitsuo AIHARA ◽  
Koichi HAGIYA ◽  
Akiko NISHIURA ◽  
Kazuo ISHII ◽  
...  

2010 ◽  
Vol 132 (1-3) ◽  
pp. 173-176 ◽  
Author(s):  
Naceur M'hamdi ◽  
Rafik Aloulou ◽  
Mahdi Bouallegue ◽  
Satinder K. Brar ◽  
Mohamed Ben Hamouda

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