ABSTRACT: Gilts that reach puberty at an earlier age
with more backfat have greater lifetime productivity.
Increased growth rates generally promote earlier age
at first estrus; however, an association of age at first
estrus with discrete measures of body fatness remains
controversial. We tested the hypothesis that metabolic
state as determined by concentrations of plasma urea
nitrogen (PUN), which reflect lean tissue growth, were
correlated with age at first estrus. Blood samples were
collected from gilts (n = 337) at 102, 123, and 145 d of
age during development. Concentrations of albumin,
creatinine, glucose, and PUN were determined. Body
weight and backfat thickness were determined at each
time point. From 130 to 240 d of age, gilts were monitored
for first pubertal estrus. Concentrations of creatinine
increased whereas concentrations of glucose decreased
with increasing age (P < 0.0001). Concentrations of
albumin and PUN remained relatively stable throughout