Mortality trends and comparisons between mortality risk and mortality rate of fattening pig operations in farrow-to-finish herds
2007
Koketsu, Y.(Meiji Univ., Kawasaki, Kanagawa (Japan). School of Agriculture)
Data files were collected from 134 herds which participated in a data-share program in Japan. Of 129 farrow-to-finish swine herds, 93 herds were selected for recording their growth performance over a period of three years from 2001 to 2003. A database was created by abstracting 12 three-month mortality records of each herd. Mortality risk (%) and mortality rate per 10,000 pig days (incidence density) were used for measuring mortality in fattening pig operations. The pig days were calculated as the total number of days for which pigs in a herd were fed during each three-month period. Mortality rate was defined as the number of dead pigs divided by the pig days during a three-month period X 10,000, whereas mortality risk was defined as the number of dead pigs divided by the number of an initial pig inventory and the number of pigs moved in the herd during a three-month period. Pearson correlation analysis was used to obtain a relationship between the mortality risk and the mortality rate. The 12 three-month data were analyzed by using mixed effects models for repeated measures. Tukey-Kramer post-hoc multiple comparisons were used to compare the means of the year, season and herd size groups. The overall means of the mortality risk and the mortality rate were 2.77% and 4.98 deaths per 10,000 pig days, respectively. High correlations across 12 three-month periods were found between the mortality risk and the mortality rate (r0.97, P0.05). Year effect was not associated with both the mortality risk and rate. Pigs fed in the spring and summer seasons and those in small herds (1,000 pigs) had higher mortality risks and higher mortality rates than those fed in the fall season and those in large herds (2,800 pigs) (P0.05).
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