Aluminum and acid effects on calcium and phosphorus metabolism in young growing chickens (Gallus gallus domesticus) and mallard ducks (Anas platyrhynchos).

Acidification is associated with increased mortality, reduced growth, and bone abnormalities in birds. Associated with acid deposition is an increase in aluminum availability due to solubilization from soil and other sources. (Conversely, experimental diets containing aluminum sulfate have much reduced pHs.) The present studies compare the effects of two levels of dietary acid (sulfuric acid) (0.122 and 0.56 mol H+ per kg feed; 0.056 and 0.277 mol sulfate per kg feed) and dietary aluminum (aluminum sulfate at 0.1 and 0.5%; sulfate at 0. 056 and 0.277 mol sulfate per kg feed) on bone growth, mineralization, and phosphorous/calcium homeostasis in growing birds (chickens and mallard ducks). Growth was reduced by the high acid (chicken) and aluminum (ducks and chickens) diets. A reduction in bone mineralization was observed in birds receiving aluminum-containing diets [low aluminum diet: decreased tibia ash, calcium, and phosphorus (chickens); high aluminum diet: decreased tibia dry weight, % of ash and mg; ash, calcium (chickens, ducks as % of ash), and phosphorus (chickens mg/duck, % of ash)]. Moreover, plasma concentrations of inorganic phosphate were reduced in chicks on the high aluminum diet. There were also marked decreases in bone growth and mineralization [tibia weight, ash (mg), calcium (mg), phosphorus (mg)] and plasma concentrations of 1,25-dihydroxy vitamin D3 in chicks on the high acid diet compared to those on a control diet. These changes were probably due to reduced feed intake; changes in bone indices being of a greater or similar magnitude in pairfed control. There was little change in bone indices, growth rate or feed consumption in ducklings receiving either the low or high acid diets. It is concluded that aluminum directly adversely affected bone mineralization whereas acid effects are mediated in part by changes in feed consumption.

Ontogeny of insulin-like growth factors (IGF-I and IGF-II) and IGF-binding proteins in the chicken following hatching.

The present study examined plasma concentrations of insulin-like growth factor (IGF)-I, IGF-II and IGF-binding proteins (IGFBPs) during posthatch growth and development in chickens. Three distinct proteins which bound 125I-IGF-I were observed irrespective of age or sex, these having apparent molecular weights of 22, 28, and 36 kDa. The major IGFBP present during much of the growth and development period was the 28-kDa form followed by the 36-kDa form. Plasma concentrations of IGF-II and of the 22-kDa IGFBP showed little ontogenic variation with the exception of elevated levels of the 22 kDa IGFBP in 1-day-old chicks. The circulating concentrations of IGF-I and of the 28-kDa IGFBP increased progressively between the time of hatching to reach a maximum at 6 weeks of age and subsequently declined to lower levels in adults. Somewhat similarly, the 36-kDa IGFBP increased during early pre- and posthatching growth to a maximum at 6 weeks of age. There were marked sex differences in circulating concentrations of IGF-I in young (4 week) and adult chickens and in the 36-kDa IGFBP in the adult, both being lower in females. Estrogen treatment of adult male chickens decreased the circulating concentrations of IGF-I together with the level of both the 28- and 36-kDa IGFBPs. Testosterone treatment had no effect on the circulating concentrations of either IGF-I or IGFBPs in adult female chickens. We conclude that the relative levels of IGF-I, IGF-II, and the IGFBPs change with age. In addition, circulating concentrations of estrogen may play a role in the regulation of IGF-I and IGFBPs.

Effect of acid or aluminum on growth and adrenal function in young chickens.

Acid precipitation can have a harmful effect on aquatic birds, due in part to increases in aluminum availability. Young rapidly growing (broiler strain) chickens were used as a model to examine the effects of aluminum and acid on growth and circulating concentrations of adrenocorticol hormones. Two concentrations of acid (sulfuric acid) or aluminum (aluminum sulfate) or sodium sulfate were administered to a heavy (broiler) strain of chickens for 10 days (Days 4 to 14 of age). Additional treatment groups included a control diet either fed ad libitum or pair-fed relative to the chicks on the acid or aluminum diets. Compared with the chicks receiving the control diet ad libitum, growth (body weight) was reduced in chicks on the aluminum (high and low level), acid (high level), and sodium sulfate (high level) treatments and the respective pair-fed groups. Circulating concentrations of corticosterone (B) were elevated in the chicks receiving the high dose of aluminum and the respective pair-fed control when compared with the chicks which had free access to the control diet. Thus, the increase in plasma B appears to be linked to the low food intake and not to the A1 per se. Circulating concentrations of aldosterone were increased in the chicks receiving either the high dose of aluminum or the acid relative to chicks fed the control diet (both ad libitum or pair-fed controls). However, circulating concentrations of aldosterone were unaffected by either dose of sodium sulfate employed. Thus, the increase in plasma aldosterone appears to be specific to the metabolic acidosis created by A1 or acid. It is concluded that environmental acid may either directly or indirectly influence adrenocortical function. Moreover, the present study provides evidence for the independent control of circulating concentrations of corticosterone and aldosterone in the chicken.

Effect of dietary acid or aluminum on growth and growth-related hormones in young chickens.

The effect of two concentrations of dietary acid (sulfuric acid) or aluminum (aluminum sulfate) on growth and growth-related hormones was examined in a heavy (broiler) strain of chicken between 4 and 18 days old. Growth (body weight, average daily gain, and tibial length) in chicks receiving either dietary acid or aluminum-containing diets were compared to chicks fed a control diet and to chicks fed diets containing sodium sulfate. Despite the reduced growth in acid-fed chicks, there were no changes in the plasma concentrations of growth hormone, insulin-like growth factor-I (IGF-I) and insulin-like growth factor-binding proteins (IGF-BP). However, in chicks receiving the high aluminum diet where growth was markedly depressed (by 57%), plasma concentrations of IGF-I were depressed, while those of the 36-kDa IGF-BP were elevated. The effects of acid and aluminum on growth were mediated at least partially by reductions in feed intake. Pair feeding depressed growth and tended to decrease plasma concentrations of IGF-I. Some differences were observed between acid or aluminum groups and their respective pair-fed controls. For the groups receiving the low-aluminum and both the high- and low-acid diets, values were increased compared to corresponding pair-fed controls for average daily gain, the level of the 36-kDa IGF-BP, and skeletal growth. On the other hand, high aluminum had a toxic effect in addition to reducing feed intake, with skeletal growth being reduced more in chicks receiving the aluminum diet than in the pair-fed controls.

Angiogenic activity of anterior pituitary tissue and growth hormone on the chick embryo chorio-allantoic membrane: a novel action of GH.

A useful system to evaluate the angiogenic activity of hormones and growth factors is the chorioallantoic membrane (CAM) of chick embryos. The present studies examined the angiogenic activity of chicken anterior pituitary glands and both fibroblast growth factor (FGF) and growth hormone (GH). Grafts of anterior pituitary gland evoked an angiogenic response on the CAM which was lost if the adenohypophyseal tissue was first boiled. The magnitude of the angiogenic response to anterior pituitary glands increased with the age of the donor (from a minimum 15 days of embryonic development to a maximum between 2 and 6 weeks old). In view of the similarity of the profile of the angiogenic response and the reported changes in GH secretion, the angiogenic activity of GH was then examined. Considerable angiogenic responses were observed with GH; there being increases (P < 0.05) in number of new blood vessels on the CAM of chick embryos on which native chicken GH or native bovine GH or recombinant bovine GH were added. These data support GH having an angiogenic action.