Effects of different levels of vitamins A and E on the utilization of cholecalciferol by broiler chickens.

Three experiments were conducted to determine the effects of high dietary levels of vitamins A and E on the utilization of cholecalciferol by broiler chicks. In Experiment 1, chicks were fed six levels of vitamin A (5,000, 10,000, 20,000, 40,000, 80,000, and 160,000 IU/kg). Cholecalciferol (vitamin D3) was not added to the basal diet but all birds were exposed to ultraviolet (UV) fluorescent light. Body weight was decreased only at levels of vitamin A of 80,000 IU/kg or above. In Experiment 2, birds were exposed to UV fluorescent light or no UV light, two levels of dietary vitamin A (1,500 and 45,000 IU/kg) and three levels of dietary vitamin D3 (0, 500, and 2,500 IU/kg) in a 2 x 2 x 3 factorial arrangement. The high level of vitamin A reduced (P < 0.001) bone ash but only at a marginal level of vitamin D3 (500 IU/kg) and when the birds were not exposed to UV light. In Experiment 3, birds were exposed to UV fluorescent light or no UV light, two levels of dietary vitamin E (10 and 10,000 IU/kg) and three levels of dietary vitamin D3 (0; 500 and 2,500 IU/ kg) in a 2 x 2 x 3 factorial arrangement. The high level of vitamin E significantly (P < 0.05) reduced body weight, bone ash, plasma calcium, and increased rickets but only at 500 IU/kg of vitamin D3. Feeding 2,500 IU/kg of vitamin D3 overcame the effects of the high level of vitamin E, causing a significant (P < 0.05) interaction. Ultraviolet light also prevented the detrimental effects of the high level of vitamin E. The results of these studies indicate that high dietary levels of vitamins A and E negatively affected the utilization of vitamin D3 only when D3 was present at a marginal level (500 IU/kg) in the diet but not when it was synthesized in the bird by exposure to UV light or supplemented at 2,500 IU/kg in the diet.

The influence of vitamin A on the utilization and amelioration of toxicity of cholecalciferol, 25-hydroxycholecalciferol, and 1,25 dihydroxycholecalciferol in young broiler chickens.

Three experiments were conducted to determine the influence of vitamin A on the utilization and amelioration of toxicity of cholecalciferol (vitamin D3), 25-hydroxycholecalciferol [25-(OH)D3], and 1,25-dihydroxycholecalciferol [1,25-(OH)2D3] in young broiler chicks. Two levels of vitamin A (1,500 and 45,000 IU/kg or 450 and 13,500 microg) were fed in all experiments. In Experiment 1, chicks were fed six levels of vitamin D3 (0, 5, 10, 20, 40, and 80 microg/kg). High dietary vitamin A decreased bone ash (P < 0.001), and increased the incidence of rickets (P < or = 0.02). Linear and quadratic responses to vitamin D3 levels were significant (P < 0.01) for body weight, bone ash, incidence and severity of rickets, and plasma calcium. In Experiment 2, six levels of 25-(OH)D3 (0, 5, 10, 20, 40, and 80 microg/kg) were added to the basal diet. Adding 25-(OH)D3 increased (P < 0.001) body weight, bone ash, and plasma calcium, and decreased rickets and plasma vitamin A. Adding 25-(OH)D3 overcame the reduction in bone ash produced by high dietary vitamin A showing a significant (P < 0.02) interaction. In Experiment 3, six levels of 1,25-(OH)2D3 (0, 2, 4, 8, 16, and 32 microg/kg) were added to the basal diet. High dietary vitamin A increased (P < 0.01) the incidence and severity of rickets. Adding 1,25-(OH)2D3 increased (P < 0.01) body weight, bone ash, plasma calcium, and reduced rickets and plasma and liver vitamin A. Adding 1,25-(OH)2D3 overcame the reduction in bone ash, and the increase in rickets produced by high vitamin A was significant (P < or = 0.05). These results indicate that high dietary vitamin A (45,000 IU/kg) interferes with the utilization of vitamin D3, 25-(OH)D3 and 1,25-(OH)2D3, increasing the requirement for each of them. Moreover, 45,000 IU/kg of dietary vitamin A ameliorated the potential toxic effects of feeding high levels of vitamin D3, 25-(OH)D3 and 1,25-(OH)2D3 to young broiler chickens. Further work is necessary to find the minimum levels of these vitamins needed to cause these effects.

Effects and interactions of dietary levels of vitamins A and E and cholecalciferol in broiler chickens.

Four experiments were conducted to determine the effects and interactions of feeding different levels of vitamins A, cholecalciferol (vitamin D3), and E on broiler chicks. In Experiment 1, chicks were fed marginal vitamin D3 (500 IU/kg) and increasing dietary levels of vitamin A (5,000, 10,000, 20,000, 40,000, 80,000, and 160,000 IU/kg). Bone ash was reduced by 10,000 IU/kg of vitamin A in the diet and at vitamin A levels above 20,000 IU/kg of diet body weight was reduced. In Experiment 2, two levels of vitamin A (1,500 and 15,000 IU/kg) and six levels of vitamin E (10, 500, 1,000, 2,500, 5,000, and 10,000 IU/kg) were added to the basal diet. High levels of vitamins A and E significantly (P < 0.001) reduced bone ash. The vitamin A x E interaction was significant (P < or = 0.05) for rickets. In Experiment 3, the same two levels of vitamin A as Experiment 2 and six levels of vitamin D3 (500, 1,000, 1,500, 2,000, 2,500, and 3,000 IU/kg) were added to the basal diet that contained 10,000 IU/kg of vitamin E. Body weight and bone ash were increased by increasing vitamin D3 with a corresponding reduction (P < or = 0.05) in rickets. In Experiment 4, three levels of vitamin A (1,500, 15,000, and 45,000 IU/kg), three levels of vitamin D3 (500, 1,500, and 2,500 IU/kg), and three levels of vitamin E (10, 5,000, and 10,000 IU/kg) were added to the basal diet. Significant negative responses (P < or = 0.05) to increasing dietary vitamin A were observed for bone ash, rickets, and plasma and liver vitamin E. A significant (P < 0.001) increase in bone ash and plasma calcium with a corresponding reduction in rickets was observed by increasing vitamin D3. Increasing dietary vitamin E adversely affected (P < or = 0.01) bone ash, plasma calcium, and plasma and liver vitamin A concentrations. These results indicate the need for making feed with the proper ratios of vitamins A, D3, and E.

Effects of dietary magnesium excess in White Leghorn hens.

The effects of excess dietary magnesium on White Leghorn laying hens were investigated in two experiments and a third experiment looked at the effect of dietary phosphorus on excess magnesium in the diet. In Experiment 1, magnesium levels of 0.15, 0.8, and 1.2% were fed in a diet containing 2.5% calcium to hens 30 wk of age for 5 wk. A control diet with 3.5% calcium and 0.15% magnesium was also fed. In Experiment 2, hens 65 wk of age fed 3.5% calcium were fed dietary magnesium levels of 0.15, 0.36, 0.53, 0.76, and 0.91% for 4 wk. In these two experiments, excess magnesium reduced egg production, decreased feed consumption, decreased body weight, decreased percentage eggshell, reduced plasma calcium, and increased plasma magnesium and tibia magnesium but changes seen in tibia weight, percentage ash, and tibia calcium and phosphorus were variable. More changes from feeding excess magnesium were seen in the young, high producing hens in Experiment 1. In Experiment 3, hens 50 wk of age were fed a marginal calcium level (2.5%) with an excess of magnesium (0.8%) and a control level of available phosphorus (0.45%) and this was compared to a low (0.25%) and a high level (0.9%) of available phosphorus for a 4-wk experimental period. At the end of the experimental period, hens fed low phosphorus had lower egg production and lower feed consumption than the hens fed higher levels of phosphorus. Body weight was lower in the hens fed the two lower levels of phosphorus. Percentage eggshell was lower than the controls when fed low phosphorus and higher when fed high phosphorus. These results suggest that high phosphorus diets are better than low phosphorus diets when excess magnesium is fed to laying hens. Further study is needed to investigate the role of phosphorus when excess magnesium is fed.

Quantitative requirement for cholecalciferol in the absence of ultraviolet light.

Studies were conducted to determine the basic requirement of the bird for cholecalciferol in the absence of ultraviolet light by utilizing filter sleeves on fluorescent lights in the room and brooder. In Experiment 1, some pens were fitted with filter tubes and some lights were turned off. All the birds received a cholecalciferol-deficient diet. Birds with ultraviolet light excluded grew slowly, developed rickets (95%), had low plasma calcium, and low bone ash (27%); whereas birds exposed to the fluorescent light had normal growth and plasma calcium, slightly low bone ash (38%), and some rickets (12%). Experiments 2 and 3 were conducted to determine the amount of cholecalciferol that must be added to the diet under conditions in which ultraviolet light was excluded. In Experiment 2, the highest level of cholecalciferol fed was 400 ICU/kg. This level was not sufficient to permit the chickens to have weight gain or bone ash equal to the birds receiving the ultraviolet light. The birds receiving 400 ICU/kg of diet also had a 77% incidence of rickets compared with 20% for the birds receiving ultraviolet lights. In Experiment 3, when birds received 800 or 1,600 ICU/kg of cholecalciferol in the diet, they grew and were comparable to those receiving ultraviolet light for the criteria measured.

Histomorphometric bone properties of sexually immature and mature White Leghorn hens with evaluation of fluorochrome injection on egg production traits.

White Leghorn hens were injected i.p. with fluorochromes beginning at 18, 37, and 43 wk of age. Sections of the right femur were collected in ethanol and formalin approximately 2 wk later. Dynamic and static bone variables were determined in both age groups, and the effects of fluorochrome injection on egg production was assessed in the older hens. Fluorochrome bone labeling was nontoxic. Injection of fluorochrome did not affect BW or feed consumption in either age group or egg production traits in laying hens. Fluorochrome labeling was found in the femoral cortex of sexually immature hens. The mineral apposition rate of the periosteal surface was 3.08 micrometers/day and of the osteonal surface was 2.69 micrometers/day. No uptake of fluorochrome label was observed on the periosteal or osteonal surfaces of cortical bone of laying hens. Sexually mature hens had decreased femoral cortical widths, less percentage cortical bone, and more cortical endosteal surface than sexually immature hens. The diffuse labeling of the medullary bone of laying hens indicated active medullary bone mineralization. The central area of the femur cross-section inside of the cortex was examined. Sexually mature hens had less bone area, more bone perimeter, and more bone perimeter covered by osteoclasts in the lamellar cancellous and medullary bone compared with sexually immature hens. Results indicated that the development of osteopenia in hens with the onset and progression of lay may be related to increased resorptive surface of bone and loss of structural and nonstructural bone.

Pathology of experimental vitamin D deficiency in turkeys and the effects of various vitamin D supplements.

One-day-old poults fed a vitamin D3-deficient diet were examined for clinical, biochemical, and morphological changes at 14 days of age. Changes in these parameters were compared at 15.5 and 17 days of age after one of the following vitamin D-replacement therapies was provided: water-soluble vitamin-mineral packs that contained vitamin D3; vitamin D3 in the feed; or vitamin D, 1,25-dihydroxyvitamin D3 in the feed. The vitamin D3-deficient poults were lame and had significant decreases in weight gain and in longitudinal skeletal growth. None of the therapies alleviated all these changes, but clinical lameness subsided in poults provided 1,25-dihydroxyvitamin D3. Calcium concentrations were significantly improved by all therapies. Treatment with vitamin D3 in the feed and water significantly increased 25-hydroxyvitamin D3 concentrations in vitamin D-deficient poults. The growth plate zones, with the exception of the mineralized hypertrophied zone, were all increased in length and not modified by treatment. However, the mineralized hypertrophied zones in the 1,25-dihydroxy-vitamin D3 group and the group receiving vitamin D3 in the water were comparable to that in the controls on day 15.5.

Localization of chicken parathyroid glands through vital staining.

Five, fat-soluble dyes and one, metachromatic tissue dye were administered to White Leghorn hens and broilers to determine how these compounds would color parathyroid tissue for subsequent gland localization. Sudan black, sudan red, canthaxanthin, oil red O, beta-apo-8'-carotenal, and toluidine blue O were administered orally in gelatin capsules once a day for 1, 2, or 3 days before slaughter. The dyes were administered at approximately 100 mg/dose. The carotenoid pigments were given at 200 mg/dose. Two administrations were required to develop sufficient visible staining. All dyes except the toluidine blue O were visibly deposited in the parathyroid glands. Sudan black resulted in the greatest contrast with surrounding adipose tissue. Male broilers 3 wk of age that were given one dose of sudan black showed gland definition comparable to that seen in the hens after two doses. Male broilers 5 wk of age showed less gland definition when given sudan black or sudan red for 1 or 2 days. A histological examination indicated that the fat-soluble dyes were located extracellularly. These results indicate that sudan black can be used to visually identify the parathyroid glands of chickens.

Effects of monensin feeding and withdrawal on fat pad adipocyte size in female broilers.

Abdominal fat pad adipocyte size was determined in two experiments to evaluate the effect of monensin feeding and withdrawal on female broilers. In Experiment 1 at 49 days of age mean adipocyte sizes were: 49.2 micron, unmedicated controls; 50.0 micron, medicated controls; 55.6 micron, medicated birds with 5-day withdrawal period; and 55.1 micron medicated birds with 10-day withdrawal period. In Experiment 2, adipocyte sizes of medicated controls were 62.5 and 63.5 micron at 44 and 51 days, respectively. All medicated birds received 120 ppm dietary monensin. In broilers subjected to drug withdrawal for 7 days, adipocyte size was 60.1 micron at 44 days and 68.8 micron at 51 days after the drug withdrawal period. There were no significant differences (P less than .05) in adipocyte size among treatments in either experiment.

Magnesium-induced catharsis in chicks.

High magnesium (Mg) diets induce diarrhea in chicks. Addition of 0.3, 0.5 or 0.9% Mg (as MgO) to a corn-soy basal diet caused a dose-related lower gut passage time (GPT) (the first appearance of colored markers from feed in excreta), with the threshold for catharsis being approximately the 0.3% addition. Supplementation of the high Mg diets with a water-absorbent clay did not change the chicks' GPT. The beta-adrenergic blocking agent propranolol (1.68 mg/kg body wt) or the alpha-adrenergic blocking agent phenoxybenzamine (0.28 mg/kg body wt) did not effect the GPT of chicks fed high Mg diets. However, both the muscarinic blocker methscopolamine (0.12 mg/kg body wt) and the serotonergic blocker methysergide (0.2 mg/kg body wt) resulted in a higher GPT of chicks fed high Mg diets compared to corn-soy fed control chicks. Analysis of the osmotic load of excreta or intestinal contents of high Mg-fed chicks showed no differences from osmotic loads of control-fed chicks. When the osmotic loads observed were partitioned into mineral cationic and anionic components, the Mg content was found to be higher in intestines of chicks, but this higher Mg was paralleled and/or surpassed by chloride (Cl) content. From these data the authors conclude that Mg-induced cartharsis is due not simply to the hyperosmotic effect of Mg per se but to neural or endocrine arcs that affect the secretion or absorption of Cl as well.

Effects of monensin feeding and withdrawal time on growth and carcass composition in broiler chickens.

Four experiments were conducted to evaluate the effect of monensin feeding and withdrawal on broiler performance and carcass characteristics. It was shown that monensin (100 ppm) feeding depressed growth. Withdrawal of monensin from the feed for 5 or 7 days produced higher feed consumption and weight gain values compared with those of unmedicated broilers. Increasing the withdrawal period to 10 days did not produce greater growth improvement. Whole body composition of protein, water, lipid, and ash were not significantly affected by monensin feeding or withdrawal. Abdominal fat pads of unmedicated female broilers were significantly larger than those of broilers medicated with monensin even when expressed as a percentage of body weight (3.53 vs. 2.99%). Amount of lipid per fat pad was also higher in unmedicated broilers than in medicated broilers (43.5 vs. 30.6 g). Values for fat pad weight (as a percentage of body weight) and grams of lipid per fat pad of unmedicated birds were not different from those measures in medicated birds after 5 or 7 days of withdrawal. Fat pad weights and lipids per fat pad of birds after 10 days of monensin withdrawal were intermediate between those of unmedicated and monensin-medicated broilers. Monensin feeding or its withdrawal for 5 or 10 days did not influence the female broiler abdominal fat pad lipid fatty acid composition when compared with that of unmedicated fat pad lipid.

Effect of short-term feed deprivation on shell quality in laying hens.

Hens with feed withheld for 24 hr had poorer shell quality for the next 3 days. Hens with feed withheld for the first 8 hr (0400 to 1200 hr) of the 16-hr light cycle showed no decline in shell quality, but those with feed withheld the last 8 hr (1200 to 2000 hr) had poorer shell quality on the following day. When the period from 1200 to 2000 hr was divided into 2 periods (1200 to 1600 hr and 1600 to 2000 hr), feed restriction during the 1600 to 2000-hr period caused a decline in shell quality on the next day, but removal during the 1200 to 1600-hr period had no effect on shell quality. Shell quality was related to the feed intake of the hens, because about 34% of their feed intake was during the period 1600 to 2000 hr. Hens fed a low Ca diet (.7%) from 1200 to 2000 hr had poorer shell quality but not as poor as those with feed withheld. Feeding a high Ca diet (7.6%) from 0400 to 1200 hr prior to feed restriction from 1200 to 2000 hr, or giving oyster shell during the period of feed removal, improved shell quality, but not to the level of the full-fed birds. Daily feed restriction from 1200 to 2000 hr caused a reduction in shell quality for the first 4 days after which shell quality returned, but a slight decline in egg production was noted. These hens were able to consume approximately 70% of the feed consumed by the full-fed birds.

Experimental rickets in broilers: gross, microscopic, and radiographic lesions. II. Calcium deficiency.

Day-old broiler chicks were fed a calcium-deficient diet for 30 days. Gross, microscopic, and radiographic examinations of the proximal tibiotarsus were done at 2, 3, and 4 weeks of age. In 2-week-old chicks, the growth-plate proliferating-prehypertrophied zone (P-PHZ) was variably lengthened and disorganized, cartilage columns of the degenerating hypertrophied zone and metaphyseal primary spongiosa were shortened, and bone spicules of the secondary spongiosa were bordered by increased osteoid. In 3-week-old chicks, lesions were either similar or more pronounced, with the additional finding of metaphyseal peritrabecular fibrosis. In 4-week-old chicks, the P-PHZ decreased in relative length, osteoid seams and fibrous connective tissue were less prominent, and tibial dyschondroplasia-like lesions were present. Results demonstrated that dietary calcium deficiency produced rachitic lesions, that the lesions were very different from those of phosphorus deficiency or calcium excess, and that the lesions were variable over time.

Experimental rickets in broilers: gross, microscopic, and radiographic lesions. III. Vitamin D deficiency.

Day-old broiler chicks were fed a vitamin D-deficient diet for 30 days. Gross, microscopic, and radiographic examinations of the proximal tibiotarsus were done at 2, 3, and 4 weeks of age. In 2-week-old chicks, there was variable lengthening and disorganization of the proliferating-prehypertrophied zone (P-PHZ), resorption of cartilage spicules in the degenerating hypertrophied zone and primary spongiosa, and lengthening of bone spicules in the secondary spongiosa; many bone surfaces were lined with increased osteoid. In 3-week-old chicks, there was a tendency for the P-PHZ to decrease in relative length and for cartilage spicules to increase in length. In 4-week-old chicks, however, there was marked lengthening of the P-PHZ, resorption of cartilage spicules, and replacement of the metaphysis with irregularly oriented islands of woven bone, osteoid, and loose fibrous connective tissue.

Experimental rickets in broilers: gross, microscopic, and radiographic lesions. I. Phosphorus deficiency and calcium excess.

Day-old broiler chicks were fed diets high in calcium or low in phosphorus for 30 days. Chicks in both groups had similar gross, microscopic, and radiographic lesions. At 2 weeks, the growth-plate degenerating hypertrophied zone (DHZ) and metaphyseal primary spongiosa were lengthened and decreased in radiopacity. Metaphyseal vessels extended to the growth-plate hypertrophied zone (HZ), and osteoid seams were widened. At 3 and 4 weeks, lesions were similar; however, folding fractures were common and cartilage columns of the metaphysis were thinned and replaced with increased woven bone.

A simple procedure for preparing and staining undecalcified sections of avian growth plate and metaphysis.

This report describes an inexpensive, rapid technique for preparing 4-micron-thick undecalcified sections of avian growth plate and metaphysis using paraffin embedment, rotary microtomes, and disposable knives. Sections were stained by von Kossa's technique with a hematoxylin-and-eosin counterstain.

Magnesium toxicity: bone lesions.

Broiler chicks fed corn-soy rations supplemented with toxic levels of magnesium from one day of age grew poorly, developed diarrhea, and exhibited characteristic skeletal abnormalities. Tibiae from magnesium intoxicated chicks were shortened, thickened, and bowed. Percent tibial ash was greatly reduced. Upon microscopic examination, the bone lesion appeared rachitic as evidenced by widened and lengthened growth plates, excessive osteoid seams on endochandral bone, and osteoid or bone capped metaphyseal blood vessels with very few associated osteoblasts. Tibial calcium to phosphorus mass ratios decreased while tibial magnesium to phosphorus mass ratios increased concomitantly with increased dietary magnesium. Calcium and phosphorus homeostasis was possibly affected as evidenced by a general decrease in size and cellularity of parathyroid glands and a general increase in size and cellularity of ultimobranchial glands.

Magnesium toxicity: effect on phosporus utilization by broiler chicks.

Excessive dietary magnesium (Mg) (.3, .5, and .9% additions to a corn-soy basal diet) fed to broiler chicks was found to be cathartic and significantly decreased 28-day body weight, significantly increased mortality, and induced leg abnormalities. Increasing dietary phosphorus (P) significantly ameliorated the detrimental effects of Mg toxicity except at the highest Mg level (.9% addition). Increasing dietary chloride (Cl) significantly increased body weights of Mg intoxicated chicks and significantly reduced the hypermagnesemia induced by excessive dietary magnesium. Excessive dietary magnesium increases the need for dietary P. Failure to monitor Mg content of diets may contribute to the ambiguity of ascertaining the P requirement of domestic fowl.

Comparison of lipoprotein lipase activities in chickens and turkeys.

Three experiments were conducted to compare the role of lipoprotein lipase in fatty acid metabolism in chickens and turkeys. An initial experiment to determine the effect of fasting on the enzyme activity of chicken and turkey muscle and adipose tissues demonstrated that fasting decreased the lipoprotein lipase activity of adipose tissue, while increasing the enzyme activity of muscle tissue in chickens only. Quantitatively, turkey samples showed a greater enzyme activity in both muscle and adipose tissue than the chicken samples. In a second experiment both insulin and epinephrine added in vitro signifiacntly increased activity of lipoprotein lipase from chicken adipose tissue, but not from turkey adipose tissue. In a third experiment conducted to examine the effects of carbohydrate and fat feeding on lipoprotein lipase activity of chicken and turkey adipose tissue, fat feeding increased activity the greatest amount. In both species, refeeding, regardless of the energy source, produced a significant increase in the lipoprotein lipase activity of adipose tissue. Differences in lipoprotein lipase activity does not appear to be related to differences in rate of body fat deposition observed between broiler chickens and turkeys.

Effect of dietary aflatoxin on vitamin D3 metabolism in chicks.

Male broiler chicks were fed diets containing either O (control) or 2.5 p.p.m. aflatoxin (toxin) for four weeks. A group of eight birds fed each diet was infected intravenously with radioactive vitamin D3 (D3) and a second group with radioactive 25-hydroxy vitamin D3 (25-OH D3). Plasma was obtained 24 hr. after dosing with D3 and 6 hr. after dosing with 25-OH D3. The vitamin D metabolites were extracted from the plasma an chromatographed on Sephadex LH-20 for separation. The four peaks of radioactivity separated corresponded to D3, 25-OH D3, 24,25-dihydroxy vitamin D3 (24,25-(OH)2D3) and 1,25-dihydroxy vitamin D3 (1,25-(OH)2D3). Percentages of radiation in each peak were (1) controls given D3--6.55, 64.30, 5.94 and 4.04; (2) toxin given D3--10.05, 56.96, 8.95 and 4.68; (3) control given 25-OHD3-2.16, 85.80, 4.11 and 2.04; and (4) toxin given 25-OH D3--1.53, 79.84, 5.56 and 2.14. The only significant differences between the control and toxin groups were in D3 and 24,25-(OH)2D3 in chicks given D3. Even these changes were small and the data would suggest that feeding 2.5 p.p.m. aflatoxin for four weeks does not greatly alter vitamin D metabolism.