Production of growing male pigs: a meta-analysis

Abstract

A meta-analysis was carried out in order to study performance, carcass characteristics and nutritional interactions in castrated, entire and immunocastrated males. A total of 27 studies were used in the database, totaling 2917 animals. The meta-analysis followed three sequential analyses: graphical, correlation and variance–covariance. Entire males showed feed intake 9% lower (P<0.05) than surgically castrated males and 11% lower (P<0.05) than immunocastrated pigs. Weight gain was higher (P<0.05) in immunocastrated pigs in comparison to entire (9%) and castrated (12%) males. Daily weight gain showed positive correlation (P<0.05) with crude protein intake in all sex categories. The intercepts in the equations estimating the total lysine intake depending on the weight gain were 15.3; 20.4 and 22.3g for surgically castrated, immunocastrated and entire males, respectively, indicating empirically that the entire males have higher lysine requirement for maintenance in comparison to surgically castrated pigs. Hot carcass weight and carcass yield did not differ (P>0.05) between treatments. However, castrated males showed lower lean meat content (P<0.05) in comparison to immunocastrated (5%) and entire (7%) males. The backfat thickness of surgically castrated pigs was 21% higher (P<0.05) relative to immunocastrated and 27% higher (P<0.05) in comparison to entire pigs. Performance responses differ in surgically castrated, entire and immunocastrated male pigs. The meta-analysis indicated that the nutritional variables and maintenance requirements in different sexual categories of pigs should be considered in future research studies.