Effects of Gradation in Protein-Calorie Restriction on the Hypothalo-Pituitary-Gonadal Axis in Young Domestic Fowl

Abstract

The effect of protein-calorie restriction on the circulating concentration of luteinizing hormone (LH) was investigated in the young domestic fowl. Two-week-old broiler chicks were fed isocaloric synthetic diets with varying levels of soy protein for a period of 14 days. Growth rate, as indicated by body weight, was decreased as the level of protein in the diet was reduced. Body weights of birds on a 3% protein diet were only 29.7% that of birds on a 24% protein diet. Severe protein-calorie restriction was also associated with depressed plasma LH levels in birds of both sexes, with male birds appearing to be more sensitive to this deficiency. A reduction of protein in the diet from 24% to 3% was associated with a 69% decrease in LH in males and a 43% decrease in females. In addition to lower circulating concentrations of LH, protein-calorie restriction was associated with a reduction in gonadal weight. Testes weights in birds on a 3% protein diet were only 16% of those on a 24% protein diet. Studies with synthetic luteinizing hormone releasing hormone (LHRH) indicated that protein-calorie restriction alters luteinizing hormone secretion via a hypothalamic effect.

Body weight and/or fatness as potential determinants of the onset of egg production in broiler breeder hens

“…Undernutrition may produce a distortion of the normal growth pattern, with some parts of the body having priority of growth over others, and with some body functions appearing only after the attainment of a certain size. In pigs this is true for the production of luteinising hormone (Dickerson et al, 1964), and in chickens, too, the secretion of this hormone, which is essential for ovulation, may be linked with the attainment of a particular size (Buonomo et al, 1982). It should be emphasised, however, that no proof has been offered in this study that body weight is a causal factor rather than only a correlate of the start of lay, nor has the mechanism been determined by which weight influences or initiates the onset of egg production.…”

Reproductive management of poultry

“…71,72 In young chickens, protein deficiency also has been demonstrated to rapidly cause atrophy of gonads, decrease circulating concentrations of LH and depress responsiveness to GnRH. 73…”