A. Prunier et al., METABOLIC AND ENDOCRINE CHANGES ASSOCIATED WITH UNDERNUTRITION IN THEPERIPUBERTAL GILT, Journal of animal science, 71(7), 1993, pp. 1887-1894
The effect of feed restriction on circulating metabolites and metaboli
c and gonadotropic hormones was determined in Large White gilts. From
25 kg BW and 80 d of age, control gilts (CTRL, n = 10) were fed close
to ad libitum intake, whereas restricted-fed gilts (REST, n = 10) were
offered approximately 50% of the CTRL diet. Estrus was detected with
a mature boar. Serial blood samples were collected at approximately 16
0 and 210 d of age from 0800 to 2000. A meal was supplied at 0900, and
an i.v. injection of GnRH (80 ng/kg BW) was given at 1600. The gilts
were slaughtered at 220 d of age. No REST and four CTRL gilts exhibite
d their first estrus between the two series of blood samplings. Feed i
ntake, daily gain, and fat content of the carcass were reduced by 50%
in REST gilts (P < .001). Preprandial concentrations of free fatty aci
ds were significantly lower in CTRL gilts at 210 d of age than at 160
d and than in REST gilts at both ages. Within the CTRL group, concentr
ations were lower (P < .05) at both ages in gilts pubertal before 210
d than in others. After the meal, plasma insulin and urea increased in
all gilts, whereas glucose increased and free fatty acids decreased i
n all except the 210-d CTRL gilts. The afternoon concentration of cort
isol was slightly higher (P = .09) in REST than in CTRL gilts. The num
ber of pulses and mean and interpulse concentrations of growth hormone
did not show any clear variation with feed level and age. Before inje
ction of GnRH, plasma FSH decreased with age in CTRL gilts, whereas ba
sal LH increased with age in all gilts, and the number of LH pulses in
creased with feed level (P < .05). Within the CTRL group, the number o
f LH pulses was significantly higher in gilts that were pubertal befor
e 210 d than in others. The highest gonadotropin concentrations after
GnRH were detected in REST gilts at 160 d of age. In conclusion, this
experiment shows that the time needed for the transition from a fed to
an unfed state after the withholding of feed increased during growth
of the gilt. This change seems to be associated with pubertal maturati
on and variations in LH secretion.