Mitigating effect of dietary bromelain on inflammation at the injection site of food-and-mouth disease vaccine

The vaccination for foot-and-mouth disease (FMD) is an effective way to control FMD. However, the injection of FMD vaccine causes abnormalities in pork meat by the incidence of lesions at the injection site. This study was conducted to investigate the inhibition effects of dietary bromelain, a natural protease derived from pineapple stems, on the incidence of lesions at the vaccination site on pigs. A total of 335 pigs (LYD [Landrace ${\times}$ Yorkshire ${\times}$ Duroc]; 7-week-old) were randomly allotted to two dietary treatments: control (basic diet) and bromelain treatment (diet supplemented with bromelain 1 kg/ton). The injection of FMD vaccine was conducted on 56- and 84-day-old pigs. Pigs with the bromelain treatment were fed a diet supplemented with bromelain for 14 days from 5 days before the vaccine injection. After slaughtering the pigs, the number of carcasses that had abnormal meat at the injection site of the vaccine and the amount of abnormal meat, discarded meat, and trimmings were recorded. Pork from the bromelain treated pigs had a lower incidence of abnormal meat caused by vaccine injection as well as a lower amount of abnormal meat, discarded meat, and trimmings than those of the control (p < 0.05). Our result suggests that dietary bromelain could improve the quality of pork meat by inhibiting incidence of lesions at the vaccine injection site.