C. G. Scanes

Growth hormone and prolactin secretion in growing domestic fowl: Influence of sex and breed

Plasma growth hormone (GH) and prolactin concentrations were measured between 1 and 24 weeks of age in both sexes of a laying strain of chickens and from 1 to 9 weeks of age in broiler cockerels. 2. GH and prolactin concentrations were highest in young birds and higher in males than in females. 3. In both sexes GH and prolactin concentrations were correlated inversely with age and body weight and positively with relative weight gain. 4. Differences in growth rate between broilers and layers were related to differences in blood GH concentrations. 5. Water deprivation for periods of 6, 12, 18 or 24 h increases plasma prolactin markedly but did not affect GH secretion significantly.

Functional differentiation of the embryonic chicken pituitary gland studied by immunohistological approach

Abstract The cephalic and caudal lobes of the embryonic chicken pituitary of different embryonic ages were investigated by immunohistological methods. The onset of production of ACTH, GH, and PRL was determined. ACTH antiserum was raised against synthetic ACTH, while GH and PRL antisera against these hormones were purified from chicken adenohypophysial tissue. The occurrence of secretion of ACTH and GH was detected 1–3 days earlier than described previously by other authors (viz. ACTH by 7 days of incubation and GH by 12 days). It seems also to be reasonable to accept that the first signs of PRL secretion appear on the sixth day of incubation. The localization of the different trophic hormone-producing cells, however, agreed with the findings available in the literature. The specificity of the different antisera used in this study is thoroughly discussed on the grounds of different types of control investigations.

Diurnal-nocturnal changes in food intake, gut storage of ingesta, food transit time and metabolism in growing broiler chickens: a model for temporal control of energy balance.

1. Diurnal-nocturnal changes in food intake, gut storage of ingesta, food transit time and heat production were studied in male broiler chickens reared under a 14L:10D lighting schedule (lights on from 06.00 to 20.00 h). 2. Food consumption during the scotophase was negligible. Peak food consumption during the photoperiod occurred at the beginning of the photoperiod and in the late afternoon. 3. During the photoperiod, the crop and proventriculus/gizzard contained only small quantities of ingesta. However, at the beginning of the scotoperiod, dried ingesta content of crop and proventriculus/gizzard increased by 10.5- and 2.76-fold respectively. This increase was followed by a gradual decrease towards the end of the scotoperiod. 4. Food transit time during the scotoperiod was significantly longer than that during the photoperiod. 5. The daily pattern of heat production closely followed the 14L:10D lighting schedule. Total heat production during darkness averaged 53% of total heat production during the photoperiod. 6. It was estimated that the storage of energy (as ingesta) in the crop and proventriculus/gizzard, followed by its gradual release and the increased food transit time during the night, contributed 75.5% of nocturnal energy needs. It must be recognised that these mechanisms play a major role in the energy balance of the growing chicken during periods without food intake.

Influence of chronic melatonin implantation on circulating levels of catecholamines, growth hormone, thyroid hormones, glucose, and free fatty acids in the pigeon

Subcutaneous implantation of melatonin pellets (2 mg melatonin + 30 mg beeswax) for a period of 12 weeks, with reinforcement of implants every 2 weeks, caused significant increases in plasma levels of glucose and growth hormone (GH). Plasma levels of thyroxine (T4) were lower and the triiodothyronine (T3)/T4 ratio was higher in the melatonin-treated pigeons. However, melatonin treatment produced no significant effect on plasma levels of free fatty acids (FFA), T3, epinephrine (E), and norepinephrine (NE), although trends (P greater than 0.05) toward slight increases in FFA and T3 and decreases in E and NE were apparent. Since melatonin treatment caused increases in the levels of plasma glucose and GH and not in those of the other substances measured, it is suggested that melatonin enhances carbohydrate metabolism in preference to lipid metabolism in resting pigeons during the day (photophase) when pineal and circulating levels of melatonin are normally lower than during night (scotophase).

Variations in plasma prolactin, thyroid hormones, gonadal steroids and growth hormone in turkeys during the induction of egg laying and moult by different photoperiods

1. Concentrations of prolactin, growth hormone, testosterone, progesterone, thyroxine and triiodothyronine were measured in the blood plasma of female turkeys during successive periods of egg laying, a decline in lay, a moult induced by a short photoperiod (6 light: 18 dark) and a resumption of egg laying induced by a long photoperiod (16L:8D). 2. Concentrations of prolactin, growth hormone, testosterone and progesterone were higher in laying birds than in birds which were moulting or not laying. 3. The concentration of testosterone, but not of the other hormones studied, increased significantly during the period of profuse moult. 4. Concentrations of the thyroid hormones did not change with the varying physiological condition of the birds. However, the concentration of thyroxine was depressed by the long photoperiod.

Diurnal variations in serum luteinizing hormone, growth hormone, and prolactin concentrations in intact and pinealectomised chickens

Abstract Diurnal variations in luteinizing hormone and prolactin have been demonstrated in sera from immature cockerels. Pinealectomy significantly altered these patterns of hormone secretion. No diurnal pattern in growth hormone concentration was seen in intact or pinealectomised birds.

Seasonal changes in body weight, fat depots, and plasma levels of thyroxine and growth hormone in free-living great tits (Parus major) and willow tits (P. montanus)

Annual changes in body weight, fat depots, and plasma levels of thyroxine (T4) and growth hormone (GH) were studied in free-living great tits and willow tits. Birds were collected during six ecologically well-defined periods of the year. Special attention was given to the nonreproductive part of the year. T4 showed simple unimodal cycles in both species and both sexes, with high levels during the warmer part of the year, and low levels during the winter and spring periods. Although increasing levels were temporarily separated between the two species, they were in both cases correlated with the onset of gonadal regression and moult. Plasma levels of GH fluctuated in a much more complex pattern, and no obvious and consistent correlation to any extrinsic or intrinsic factor was found. Body weights and fat depots both showed seasonal variations that varied slightly between the two species. Values, with the exception for breeding females, were generally the highest during the autumn, winter, and spring periods.

Stimulation of growth hormone secretion in dwarf chickens by thyrotrophin-releasing hormone (TRH) or human pancreatic growth-hormone-releasing factor (hpGRF)

The basal plasma growth hormone (GH) level in adult sex-linked dwarf hens was elevated in comparison with autosomal dwarf hens and with control (Cornell K strain) laying hens. The iv administration of thyrotrophin-releasing hormone (TRH) (10 micrograms/kg) had no effect on GH secretion in control hens but slightly (1.2-fold) and transiently (for 10 min) increased the GH level in the autosomal dwarfs and greatly (8.7-fold) increased the GH level in the sex-linked dwarfs, in which it remained elevated for at least 30 min after injection. The iv administration of human pancreatic GH-releasing factor (hpGRF) (10 micrograms/kg) stimulated GH release in each strain. The response in the sex-linked dwarfs was greater than that in the autosomal dwarfs and the control hens but less than that elicited by TRH. These results suggest that the increased basal GH level in the sex-linked dwarfs results from an increased responsiveness to provocative stimulation.

Influence of triiodothyronine and growth hormone on growth of dwarf and normal chickens: interactions of hormones and genotype

The effects of dietary triiodothyronine (T3), injections of a preparation of growth hormone (GH) (purified from chicken pituitary tissue) and their combination on growth were investigated in three lines of chickens. The three lines were the Cornell K strain (K) (a single Comb White Leghorn strain), the Cornell K strain hemizygous for the sex-linked dwarfing gene (SLD), and the Cornell K strain homozygous recessive for the autosomal dwarfing gene (ADW). A dietary T3 treatment by genotype interaction was observed. Dietary T3 (0.1 ppm) decreased growth in the K line, tended to decrease growth in the ADW line while it tended to increase growth in the SLD line. Chicken growth hormone (100 micrograms/kg body wt) alone did not affect growth in any of the lines studied. There was, however, a GH treatment by T3 treatment interaction. Chicken GH overcame the growth-depressing effects of T3 in the K and ADW lines while it tended to promote growth in T3 treated SLD birds. Dwarf (SLD) chickens had higher basal circulating GH concentrations, lower circulating immunoreactive somatomedin C concentrations, and lower circulating T3 concentrations than the K or ADW chickens.

Effect of daily injections of ACTH on growth and on the adrenal and lymphoid tissues of two strains of immature fowls

1. The effects of daily injections of ACTH (30 IU/kg) or physiological saline on growth and on adrenal and lymphoid tissues of Rhode Island Red (RIR) and Light Sussex (LS) chickens were compared at 1, 2 and 3 weeks of age. 2. Saline injections retarded skeletal growth in both strains during the 1st week but only affected weight gain in LS birds. 3. Injections of ACTH depressed growth rate, caused adrenal enlargement and deplenished adrenal cholesterol to the same extent in both strains. 4. ACTH caused a greater reduction in bursal size in RIR than in LS birds. Spleen size was reduced by ACTH only in RIR birds. 5. At 2 and 3 weeks the plasma concentrations of corticosterone of RIR birds were greater than those of LS birds. Plasma corticosterone concentrations were within the normal range 24 h after the last injection of ACTH in both strains. 6. Plasma concentrations of growth hormone was unaffected by ACTH treatment in RIR birds, but it was increased in LS birds after 3 weeks of treatment.