MATERIALS AND METHODS
Animal Procedures
The research protocol was reviewed and approved
by the University of Missouri Animal Care and Use
Committee. Ninety Landrace × Large White male pigs
from primiparous sows were housed with their dams
and female littermates in traditional 1.52-m × 2.13-m
farrowing pens at the University of Missouri Swine
Farm. Sows were fed twice daily according to NRC
(1998) requirements for lactating sows. Twenty-four litters
were assigned randomly to treatment age (3, 6, 9,
or 12 d of age). Male pigs within a single litter (n = 2
to 9 male pigs per litter) were then assigned to castrated
(CAS) or noncastrated (NC) treatment groups according
to BW, for a total of 8 treatment groups: CAS
at 3 d of age (n = 12); NC at 3 d of age (n = 11); CAS
at 6 d of age (n = 12); NC at 6 d of age (n = 13); CAS at
9 d of age (n = 12); NC at 9 d of age (n = 12); CAS at 12
d of age (n = 9); NC at 12 d of age (n = 9)