Effect of milk level, season of first calving and dystocia on stayability of Iranian Holstein cows assessed by logistic regression
Research/Original Article (دارای رتبه معتبر)
This study was carried out based on the records of 206107 Holstein cows which first calved during 1992 to 2013 in 496 herds of Iran. Three criteria for stayability, Survival up to 36, 48 and 54 months after first calving, were considered. Effect of production level, calving difficulty and season of first calving on stayability was quantified using a logistic regression model and a Probit function in JMP software. Five categories of milk yield was considered based on the average and variance of within herd-calving year of mature equivalent milk production for the production level to be taken into account. Average productive life was 1294.1 days and average survival to 36, 48 and 54 months after first calving were 0.55, 0.37 and 0.22, respectively. Dystocia decreased the probability of survival to 36 months of productive life between 4 to 14 percent (P < 0.01). Survival to 36 or 54 months after first calving was decreased by 28 percent in cows with sever calving difficulty. The chance of survival decreased between 24 to 36 percent in cows delivered by surgery. The probability of survival to 36 of productive life was increased up to 71 percent in high producing cows (P < 0.01). A similar pattern was observed between production level and other measures of stayability. There were no relationship between stayability and season of first calving.
Journal of Breeding and Improvement of Livestock, Volume:2 Issue: 4, 2023
57 to 67
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