2017 Volume 54 Issue 4 Pages 168-176
In a large-scale survey regarding 46,724 Berkshire pig carcasses and 342,787 other pig carcasses conducted at two slaughterhouses in Kagoshima prefecture, the percentage of top-grade Berkshire pig carcasses (52%) was lower than that of other pig carcasses (60%) because of excessive backfat thickness (Berkshire pig, 28%;other pig, 13%). In the first experiment, the effect of sex (barrow and gilt) on the backfat thickness of Kagoshima Berkshire pigs raised under restricted feeding conditions was investigated. The backfat thickness of barrow carcasses was thicker than that of gilt carcasses. In the second experiment, the effects of the feeding method and sex on carcass evaluation were investigated to establish a management method of controlling the backfat thickness of Kagoshima Berkshire pigs in the late fattening stage on pig farms. Ninety pigs were assigned to three dietary treatment groups:intermittent feeding on a 76% total digestible nutrients (TDN76%) diet (I-T76) from 80 kg of body weight, restricted feeding on a TDN76% diet (R-T76) from 70kg of body weight, and restricted feeding on a TDN70% diet (R-T70) from 70kg of body weight. Each dietary treatment group consisted of three subgroups:barrow (n＝10), gilt (n＝10), and mixed (barrow, n＝5 and gilt, n＝5). In the barrow subgroups, the percentages of lower-grade carcasses due to excessive backfat thickness in the I-T76, R-T76, and R-T70 groups were 80%, 76%, and 50%, respectively. On the other hand, in the mixed subgroups, the percentages of lower-grade carcasses in the I-T76, R-T76, and R-T70 groups were 20%, 10%, and 10%, respectively. In the barrow subgroups, the percentages of top-grade carcasses in the I-T76, R-T76, and R-T70 groups were 20%, 33%, and 50%, respectively. On the other hand, in the mixed subgroups, the percentages of top-grade carcasses in the I-T76, R-T76, and R-T70 groups were 80%, 80%, and 70%, respectively. In all dietary treatment groups, the backfat thickness in the barrow subgroups were significantly thicker than those in the gilt subgroups. In the mixed subgroups, however, there were no differences in the backfat thickness between barrow and gilt. These results suggested that the mixed rearing of barrow and gilt, switching feed as early, and lowering TDN content of the feed for the late fattening stag are effective management methods raising the percentage of top-grade carcass of Kagoshima Berkshires pigs by suppressing excessive backfat thickness.
