THE EFFECT OF FOOD-INTAKE FROM 2 TO 24 WEEKS OF AGE ON LHRH-I CONTENTIN THE MEDIAN-EMINENCE AND GONADOTROPIN-LEVELS IN PITUITARY AND PLASMA IN FEMALE BROILER BREEDER CHICKENS

The present study describes the effect of long-term food restriction o n hypothalamopituitary function in the broiler breeder hen during the period prior to sexual maturity From 1 week of age onward, chickens we re divided into 3 groups: one group received food ad libitum (Ad lib); a second group was fed a restricted quantity of food (Res); and a thi rd group was restricted to obtain an intermediate body weight (Int) in between groups one and two, The effects of these feeding regimes on h ypothalamopituitary function were assessed by measuring the amounts of cLHRH-I stored in the median eminence (ME) and the pituitary content and plasma levels of gonadotrophins. The Res group had significantly l ower levels of cLHRH-I in the ME compared to the Ad lib animals. In al l groups, there was a major increase in cLHRH-I in the median eminence about 3 weeks before onset of lay The age of first oviposition was de layed by 2 and 6 weeks in the Int and Res groups, respectively, compar ed to the Ad lib animals, indicating that body weight gain patterns ar e not directly related to the appearance of the first egg, The attainm ent of sexual maturity may be associated with a threshold value of cLH RH-I stored in the ME in the Ad lib and Int birds. The pituitary LH an d FSH contents (after week 16) were positively related to the amount o f cLHRH-I in the ME. Plasma FSH concentrations in Ad lib and Int chick ens peaked about 3 weeks before the first oviposition and this prepube rtal peak was associated with increased pituitary FSH and ME cLHRH-I. There were however no relationships between plasma LH concentrations a nd pituitary LH content and between plasma LH and cLHRH-I amounts in t he ME, The present study demonstrates that the delayed sexual maturati on, caused by a chronic food restriction, may be associated with (1) d elayed ovarian and oviductal growth, (2) decreased cLHRH-I storage in the ME, and (3) lower levels of LII and FSH in the pituitary. These ho rmones were however not directly related to levels of food restriction , (C) 1998 Academic Press.