Biomedical subjects

H Klandorf

Publications and source records attributed to H Klandorf.

At least 19 recordsLinked to original sources

PubMed2004

Increased dietary protein elevates plasma uric acid and is associated with decreased oxidative stress in rapidly-growing broilers.

Uric acid is an important antioxidant and methods to elevate its plasma concentration may be important in animal health. In a first study, the effect of dietary protein on plasma uric acid (PUA) and glucose concentrations were determined in 3-week-old chicks. Twenty-four broiler chicks were randomly assigned to four diets: a commercial control diet (C, 20% crude protein), low protein (LP) containing 10% casein, medium protein (MP) containing 20% casein or high protein (HP) containing 45% casein for a 3-week experiment. PUA concentration increased (P<0.05) in chicks fed HP diet and declined (P<0.05) in chicks fed LP while plasma glucose concentrations were lower (P<0.05) in chicks fed the LP diet at the end of the study. In a second study, PUA and leukocyte oxidative activity (LOA) were determined in broilers fed C, LP, MP or HP diets for 4 weeks. As in the first study, dietary protein directly affected PUA concentrations. In birds consuming HP diets, PUA was negatively correlated (P=0.06) with lowered LOA. These data support the view that increases in dietary protein can increase PUA concentrations, which can ameliorate oxidative stress.

Animals↗

PubMed2003

Fructose and its effect on turkey plasma uric acid levels and productive performance.

Previous studies have shown that addition of fructose to the diet of broilers raises plasma uric acid (PUA) concentration and improves productive performance. The purpose of this experiment was to establish the effect of feeding fructose on turkey PUA concentration and productive performance. Turkey poults (n = 64) were weighed and randomly assigned to diets containing 0 (control), 5, 10, and 15% fructose with four replicates of four poults each per treatment. All diets were isocaloric and isonitrogenous. Feed and water were offered ad libitum for 14 wk. Body weights were measured biweekly throughout the study, and blood samples were drawn from wk 8 to 10 for determination of PUA concentration, leukocyte oxidative activity (LOA), and differential leukocyte counts. Relative liver size (g/kg BW) was also determined. The heaviest body weights were recorded from turkeys fed 10% fructose diet (P < 0.05). Supplemental fructose had no effect on the feed to gain ratio, relative liver size, or PUA concentrations. LOA increased in poults fed the 15% fructose diet. Turkeys fed 10 and 15% fructose diets had higher monocyte and lower polymorphonuclear lymphocyte counts (P < 0.05) compared to those fed control and 5% fructose diets. Feeding fructose to turkeys at 10% of the diet improved productive performance. However, dietary fructose had no effect on PUA or, consequently, LOA.

Animal Nutritional Physiological Phenomena↗

PubMed2001

Accelerated tissue aging and increased oxidative stress in broiler chickens fed allopurinol.

Uric acid has been hypothesized as being one of the more important antioxidants in limiting the accumulation of glycosylated endproducts in birds. Study 1 was designed to quantitatively manipulate the plasma concentrations of uric acid using hemin and allopurinol while study 2 determined their effects on skin pentosidine, the shear force value of Pectoralis major muscle, plasma glucose, body weight and chemiluminescence monitored oxidative stress in broiler chickens. Hemin was hypothesized to raise uric acid concentrations thereby lowering oxidative stress whereas allopurinol was hypothesized to lower uric acid concentrations and raise measures of oxidative stress. In study 1 feeding allopurinol (10 mg/kg body weight) to 8-week-old broiler chicks (n=50) for 10 days decreased plasma uric acid by 57%. However, hemin (10 mg/kg body weight) increased uric acid concentrations 20%. In study 2, 12-week-old broiler chicks (n=90) were randomly assigned to either an ad libitum (AL) diet or a diet restricted (DR) group. Each group was further divided into three treatments (control, allopurinol or hemin fed). Unexpectedly, hemin did not significantly effect uric acid concentrations but increased (P<0.05) measures of chemiluminescence dependent oxidative stress in both the DR and AL birds probably due to the ability of iron to generate oxygen radicals. Allopurinol lowered concentrations of uric acid and increased (P<0.05) the oxidative stress in the AL birds at week 22, reduced (P<0.05) body weight in both the AL and DR fed birds at 16 and 22 weeks of age, and markedly increased (P<0.001) shear force values of the pectoralis major muscle. Skin pentosidine levels increased (P<0.05) in AL birds fed allopurinol or hemin fed birds, but not in the diet restricted birds at 22 weeks. The significance of these studies is that concentrations of plasma uric acid can be related to measures of oxidative stress, which can be linked to tissue aging.

Aging↗

PubMed2000

Relationship between mechanical properties and pentosidine in tendon: effects of age, diet restriction, and aminoguanidine in broiler breeder hens.

Nonenzymatic glycosylation contributes to the formation of crosslinks, which leads to the structural and functional deterioration of tissue protein. The accumulation of these crosslinks in tissue proteins has been implicated in the alteration of biomechanical properties of connective tissues. The objective of this study was to determine whether tendon breaking time (TBT) and tendon breaking strength (TBS) of the flexor perforans et perforatus digiti iii tendon were related to concentrations of pentosidine in tendons (Pt) of broiler breeder hens from 8 to 125 wk of age. In addition, effects of diet restriction (DR) and a crosslinking inhibitor, aminoguanidine (AG) on Pt, TBS, and TBT were determined. Female chicks (n = 450) were randomly assigned to four treatment groups immediately after hatch: ad libitum-fed (AL); diet-restricted (DR; 60% of AL); and AL and DR groups supplemented with 1.35 mg/kg BW per day AG in the feed (AL+AG and DR+AG, respectively). In AL hens, Pt increased with increasing age (P < or = 0.0001). Concurrently, an age-related parallel increase was found for TBS (P < or = 0.0001) and TBT (P < or = 0.0001). Rate of Pt accumulation was lower in DR (P < or = 0.001), TBS (P < or = 0.01), and TBT (P < or = 0.02) hens compared with AL hens. Concentration of Pt in the AL + AG group was lower (P < or = 0.0002) than in the AL group; TBS and TBT (P < or = 0.01) followed a similar pattern. Supplementation of DR with AG did not affect Pt, TBS, or TBT. The age-related increase in Pt and loss of elasticity in the tendon was retarded by diet restriction and AG.

Aging↗

PubMed1999

Effect of thyroid hormone on concentrations of plasma calcitonin in broiler chicks.

The purpose of these studies was to determine the effect of thyroidectomy (Tx), and thyroid hormone (T3/T4) treatment on concentrations of plasma CT in chicks. In addition, the turnover of CT in Tx- and T3/T4-treated chicks was estimated using a novel nonradioactive salmon CT preparation. One-week-old broiler chicks (Gallus domesticus) (n = 75) were divided into three groups. Group I was sham-injected daily (i.m. saline), Group II was injected with 50 micrograms/day of T3/T4 while Group III was injected with the goitrogen, methimazole, (150 mg/kg BW per day) for 8 weeks. Chicks (8-9 weeks old) were implanted with catheters in the brachial wing vein and administered ruthenium-labeled salmon CT. Blood samples were collected at 30 s, 1, 2, 4, 8, 20 min, and 3 h after injection. Results showed that concentrations of plasma CT were decreased in T3/T4-injected birds. There was no significant effect of methimazole on circulating concentrations of plasma CT. The half-life of CT was significantly increased (P < 0.05) in both T3/T4-injected (n = 6; 1.34 +/- 0.16 min) and goitrogen-treated birds (n = 2; 5.81 +/- 2.83 min) compared to controls (n = 7; 54 +/- 3 s) The results demonstrate that changes in concentrations of plasma thyroid hormones can significantly affect concentrations of plasma CT.

Aging↗

PubMed1999

Protein glycosylation and advanced glycosylated endproducts (AGEs) accumulation: an avian solution?

The objectives of this study were to determine the effect of diet restriction (DR) and the crosslinking inhibitor, aminoguanidine (AG), on PMA-induced respiratory burst, concentrations of uric acid, and the rate of pentosidine accumulation in the skin (Ps) of naturally hyperglycemic broiler breeder hens. Female chicks (n = 450) were randomly assigned to four groups from 8 to 92 weeks after hatch: ad libitum (AL), diet restricted (DR), AL and DR groups supplemented with 400 ppm AG each (AL + AG and DR + AG). No consistent effects of treatments were observed on plasma concentrations of glucose. The accumulation of Ps in AL birds increased linearly with age (p < .001) and was significantly retarded in all treatment groups (p < .001). Ps in the AL + AG group was comparable to that in the DR or DR + AG groups. PMA-induced respiratory bursts in blood leukocytes were significantly retarded in DR or AG-supplemented (p < .0001) groups. Although there was a marginal increase in overall mean concentrations of plasma uric acid for the DR group, no consistent differences were observed on individual time points. It is concluded that the glycosylation process may not be the primary cause of glucose-derived crosslinks and that the accumulation of Ps can be retarded by DR and AG in broiler breeder hens.

Aging↗

PubMed1999

Age-related changes in meat tenderness and tissue pentosidine: effect of diet restriction and aminoguanidine in broiler breeder hens.

The nonenzymatic glycosylation of tissue protein contributes to the formation of crosslinks that leads to structural and functional deterioration in the long-lived tissue protein, collagen. The accumulation of these crosslinks thus contributes to the objectionable toughness of meat from aged animals, decreases its economic value, and limits its use in whole muscle foods. The objectives of this study were to determine the effectiveness of diet restriction and the crosslinking inhibitor, aminoguanidine (AG), on reducing the accumulation of crosslinks, thereby improving meat tenderness in broiler breeder hens. The glycoxidation product, pentosidine, was also measured in skin (Ps) to determine whether changes in its concentrations correlated with the changes in shear value (SV). Chicks (n = 450) were randomly assigned to four treatment groups from 8 to 125 wk after hatch: ad libitum (AL), diet restricted (DR), AL and DR groups supplemented with 400 ppm AG each (AL+AG and DR+AG, respectively). Shear value was measured with an Instron Universal Mechanical Machine. Skin pentosidine was isolated by reverse phase HPLC. There was an age-related, linear increase in SV (P<0.0001, r = 0.96), which correlated (r = 0.86) with the age-related increase in Ps in AL hens. Diet restriction retarded SV (P<0.0001) over the sampling period. In general, SV values for AL+AG were similar to those measured in DR, whereas no additive effect was observed for AG in DR birds. It was concluded that there was a linear increase in meat toughness (SV) with age that correlates with the accumulation of Ps, and that the decline in meat tenderness can be retarded by DR or AG. Secondly, the effect of DR on accumulation of Ps was so pronounced that AG supplementation did not further enhance this effect.

Age Factors↗

PubMed1998

In ovo administration of recombinant human insulin-like growth factor-I alters postnatal growth and development of the broiler chicken.

Two experiments assessed the efficacy of in ovo administration of insulin-like growth factor-I (IGF-I) to enhance skeletal muscle development and improve feed efficiency of broilers. Hatching eggs were divided into three groups: uninjected control, vehicle-injected control, and recombinant human (rh) IGF-I (100 ng per embryo). Eggs in Experiment 1 were injected on Day 1, 4, or one of Day 7 through 18 of incubation. Growth rates for Days 1 and 4 resulted in the greatest response to treatment (P < 0.01, P < 0.06 respectively). Based on these results, Experiment 2 focused on Days 1 to 4 of incubation. Results from Experiment 2 showed that there was no significant difference in hatchability among control and rh IGF-I treatment groups. Injection on Day 3 resulted in the greatest response for increased live (P < 0.035) and leg (P < 0.02) weights in both sexes. Feed efficiencies of all rh IGF-I groups were significantly (P < 0.01) improved for the first 3 wk. In ovo administration of rh IGF-I on Day 3 increased feed efficiency (6.65%; P < 0.009) in pens of mixed-sex broilers. In addition, live weights (12.3%; P < 0.002), leg weights (11.7%; P < 0.01), breast weights (9.9%; P < 0.04), and heart weights (11.4%; P < 0.02) were increased in males. These results demonstrate that in ovo administration of rh IGF-I alters feed efficiency, growth, and tissue development. This finding lends itself to significant improvements in broiler production efficiency and profitability.

Animal Nutritional Physiological Phenomena↗

PubMed1997

The effect of photoperiod and food intake on daily changes in plasma calcitonin in broiler breeder hens.

The roles of photoperiod, energy balance, and concentrations of plasma total calcium (CaT) on daily changes in plasma calcitonin (CT) were investigated in broiler breeder hens (84-100 weeks old). In the first study, broiler breeder hens (n = 24), reared on 14L:10D, were divided into two groups. One group was transferred from a restricted diet (DR) of 150 g/day to ad libitum (AL) for 14 days, while the other group remained on DR. After 2 weeks of ad libitum feeding, birds from each group (AL and DR) were bled every 2 hr for 24 hr for measurement of plasma CaT and CT. In a second study, the hens (n = 20) were transferred to continuous light (LL) for 30 days. After the 30 days, food was removed from one group for 48 hr prior to blood sampling for 24 hr at 3-hr intervals. In a third study, birds were transferred to an ahemeral light cycle (11L:10D) for 28 days. Food was removed from the birds (n = 11) for 48 hr prior to blood sampling every 3 hr for 24 hr. Four weeks later the same birds were bled again for 24 hr, but this time the birds were maintained on a restricted feeding schedule. Plasma CT was measured by a specific heterologous electrochemiluminescent (ECL) assay while plasma CaT was measured by atomic absorption. The results showed that plasma CT concentrations did not correlate with plasma CaT concentrations. Comparisons made between initial and final CaT and CT concentrations indicated an effect of stress due to repeated handling of the birds. Concentrations of plasma CT were significantly reduced in the fasted animals (P < 0.05) compared to diet-restricted controls. There was a significant increase in plasma CT during the dark period of fed animals which was abolished in animals maintained on LL or fasted. In conclusion, a surge in plasma CT requires that the hens be provided food and that they be exposed to a dark cycle.

Animals↗

PubMed1997

Effect of dietary aminoguanidine on tissue pentosidine and reproductive performance in broiler breeder hens.

Factors influencing the age-related decline in production parameters of broiler breeder hens are poorly understood. Elevated blood glucose concentrations measured in broiler breeder hens may contribute to this decline. The nonenzymatic attachment of glucose to proteins generates glycoxidation crosslinks in tissue proteins, which can ultimately impair their function. One such glycoxidation crosslink, pentosidine, has been used as a biomarker for aging studies because of its accumulation on the structural protein collagen. The objectives of these studies were to determine whether pentosidine accumulates with age in hens and whether the crosslinking inhibitor, aminoguanidine (AG), could retard this accumulation. An additional objective was to determine whether AG had any effect on production performance. In the first study, broiler breeder hens (n = 318) were randomly assigned to two groups: control and supplemented (400 ppm AG). Pentosidine was measured in the skin of the birds at 20 and 67 wk of age. Egg production was measured daily. In a second study, broiler breeder hens (n = 60) were reared as previously described. Pentosidine was measured in the skin of the birds at 20 and 68 wk of age. Results showed that pentosidine was present in the skin of the hens, and that concentrations increased with age (P < 0.001). Although pentosidine was reduced (P < 0.001) in AG-supplemented birds, production performance was not affected. In conclusion, AG retarded the rate of accumulation of pentosidine during lay in broiler breeder hens, but the reduction in pentosidine did not significantly affect production performance.

Aging↗

PubMed1996

Inhibition by aminoguanidine of glucose-derived collagen cross-linking in skeletal muscle of broiler breeder hens.

Aminoguanidine (AG) is a nucleophilic compound that inhibits nonenzymatic, glucose-derived collagen cross-linking in animal tissues. Whether AG can attenuate the accumulation of collagen cross-links in the Biceps femoris muscle of 64-wk-old broiler breeder hens as well as improve meat quality, was investigated. Eighty-four broiler breeder hens (30-wk-old) were divided into four equal groups. Each group was assigned randomly to diets supplemented with 0. 200, 400, or 800 ppm AG, respectively. Birds were fed individually, 150 g diet/d. After feeding AG for 34 wk, six birds from each group were killed and samples from the leg muscle were analyzed for changes in collagen content. Aminoguanidine decreased (P < 0.05) glucose-derived collagen cross-links in skeletal muscle as measured by fluorescence and collagen solubility. Insoluble collagen fraction decreased with increasing AG dosage, whereas acid-soluble and pepsin-soluble fractions increased with increasing AG dosage. Aminoguanidine did not affect shear force. In agreement with studies on animals with diabetes, AG is a potent inhibitor of glucose-derived cross-linking in chickens although the results from the measurements of shear force do not support its used for improving carcass quality in spent hens.

Animals↗

PubMed1995

Effect of estrogen on egg production, shell quality and calcium metabolism in molted hens.

Force-molted White Leghorn laying hens were implanted with 0.25, 0.5, 1 and 3 Compudose 200 pellets (24 mg 17 beta estradiol/pellet). Plasma estradiol increased with increasing E2 dosages in a linear manner and decreased over time in a quadratic manner (P < 0.01). E2 treatment had a nonlinear effect on total plasma calcium. Oviduct weight, shell thickness and egg weight were not significantly affected by exogenous estradiol whereas tibial bone ash percentage was increased at only one dose (P < 0.05:0.5 pellet group). Physiological supplementation with estradiol does not improve shell quality.

Animals↗

PubMed1995

Hyperglycemia and non-enzymatic glycation of serum and tissue proteins in chickens.

The objectives of these studies were to determine whether elevated plasma glucose concentrations in broiler breeder chickens (200-250 mg/dl) can result in the non-enzymatic attachment of glucose to serum proteins (fructosamine) and eventual cross-linking of tissue proteins (basement membrane thickness), and to investigate the effects of a factor that may influence this cross-linking process. In response to feeding the satiety factor calcium propionate (CaP, 1.7%), plasma glucose and fructosamine concentrations were increased (P < 0.05) from 1 to 9 weeks of age, whereas concentrations of plasma glucose and fructosamine in feed-restricted chicks were reduced for the first 7 weeks after hatch. In a second study, the age-related increase in kidney capillary basement membrane thickness was prevented (P < 0.05) by feeding the cross-linking inhibitor aminoguanidine (AG, 800 ppm) to 30-week-old broiler breeder hens for 34 weeks. The results from these studies suggest that concentrations of plasma glucose in chickens may, in fact, be exerting long-term detrimental effects on tissue proteins, which can be ameliorated by factors that limit the cross-linking reaction.

Administration, Oral↗

PubMed1993

Estrogen enhancement of Ca-, Mg-, and Ca-Mg-stimulated adenosine triphosphatase activity in the chick shell gland.

The effect of 17 beta-estradiol (E2) on Ca-, Mg-, and Ca-Mg-ATPase activity was investigated in the shell gland of 6-week-old chicks. In the first study, each of 42 birds was implanted with three E2 (Compudose-200) pellets. An additional 6 sham-implanted birds served as controls for measurements of body weight and concentrations of E2 and Ca in plasma. The activities of Mg-, Ca-, and Ca-Mg-ATPase peaked coincident with maximum plasma E2 concentrations 8 days after implantation and then progressively declined in concert with the decline in plasma E2. By 29 days after implantation, the ATPase activities were similar to those measured in birds whose E2 pellets had been removed for 11 days. Concentrations of plasma E2 dropped from peak values of 1676 +/- 317 at Day 8 to 611 +/- 180 pg/ml at Day 29. When birds whose E2 pellets had been removed were reimplanted with three pellets per bird, plasma E2 again increased to 1637 +/- 227 pg/ml. ATPase activity in these reimplanted birds also was greater (P < 0.05) than activities measured in E2-removed or E2-maintained birds. In a second study the Ca-ATPase Km and Vmax were determined in E2-implanted chicks (three pellets per bird) and compared to E2-withdrawn chicks. Five days after reimplantation of chicks with E2, there was a significant increase in both Vmax (3.38 +/- 0.21 vs 2.37 +/- 0.28 micrograms Pi/mg protein/min; P < 0.05) and Km (0.31 +/- 0.02 vs 0.25 +/- 0.01 mM Ca; P < .01).(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗

PubMed1993

Effect of estrogen in relation to dietary vitamin D3 and calcium on activity of intestinal alkaline phosphatase and Ca-ATPase in immature chicks.

The interaction between 17 beta-estradiol (E2), vitamin D3 (D3), and dietary Ca on the activities of Ca-ATPase and alkaline phosphatase (AP) was determined in the intestine of young female chicks. Chicks (n = 36) were assigned to two groups, one of which was transferred to a low Ca (0.2%) diet and the other maintained on a regular diet. One week later, each group was further divided into three subgroups and given daily injections of 0(oil), 0.25, or 0.5 mg E2/kg body wt for 14 days. E2 treatment as well as low dietary Ca significantly increased AP activity (P < 0.05), whereas the highest E2 dose decreased jejunal Ca-ATPase (P < 0.05). In a separate study, day-old chicks (n = 40) fed a purified diet supplemented with or without D3 for 24 days were divided into two subgroups and administered daily injections of either 0 or 0.25 mg estrogen 3-benzoate/kg body wt for 5 days. E2 alone or in combination with D3 failed to change Ca-ATPase activity in either the duodenum or the jejunum. However, E2 enhanced the D3-stimulated AP activity measured in the supernatant of duodenum (D3, P < 0.001; E2, P > 0.05; E2 x D3, P < 0.05) and jejunum (D3, P < 0.001; E2, P > 0.05; E2 x D3, P = 0.06). Daily injections of 0.5 mg E2/kg body wt for 6 days to 6-week-old D3-adequate chicks (n = 16) significantly increased AP activity in jejunum but not in liver and kidney (P < 0.05). In conclusion, E2 treatment enhanced the activity of intestinal AP but not Ca-ATPase. This enhancement was independent of dietary Ca, but was D3-dependent and tissue specific. The results suggest that the pubertal increase in plasma E2 can affect Ca absorption from the intestine by increasing the activity of AP.

Aging↗

PubMed1992

Characterization of a sustained-release estrogen implant on oviduct development and plasma Ca concentrations in broiler breeder chicks: modulation by feed restriction and thyroid state.

The effect of estradiol-17 beta (E2) given as a sustained-release implant (Compudose 200) on concentrations of plasma calcium (Ca) and the development of the chick shell gland has been investigated in food-restricted and thyroid hormone-treated 6- to 8-week-old broiler breeder pullets. Chicks implanted with 0, 0.5, 1.0, 1.5, 2.0, and 3.0 Compudose pellets for 24 days (n = 6/group) revealed a dose-response relationship between plasma E2 and Ca and on oviduct growth. Plasma E2 concentrations were characterized by an initial burst phase for approximately 17 days, followed by a constant release phase. Histologic examination of shell gland tissue confirmed the dose related E2-induced development of microvilliated epithelium and tubular glands over time. Feed restriction initiated at 2 weeks of age markedly increased the response to the E2 implants. Birds (n = 8/group) implanted with 2 pellets and feed restricted had increased plasma concentrations of E2 and Ca, and increased growth of the oviduct (P less than 0.01) as compared to ad libitum implanted birds. In a separate study birds (n = 6/group) had restricted access to feed from 8 weeks of age and were implanted with 0, 2, 4, or 8 pellets. At intervals from 9 to 45 days after implantation one bird from each group was killed. Although concentrations of plasma Ca were significantly greater in feed-restricted birds (P less than 0.01), oviduct growth was only marginally increased by the food restriction program. Plasma Ca concentrations in broiler breeder pullets (n = 8/group) implanted with 1 or 3 pellets and injected with T3/T4 (100 micrograms/day) were significantly decreased (P less than 0.05). Injection of thyroid hormone also marginally decreased shell gland epithelial cell height (P less than 0.05) and development of microvilli (P less than 0.05). There was no effect of the administration of the goitrogen, propylthiouracil (10 micrograms/day im), on the E2 induced development of the shell gland.

Animals↗

PubMed1992

Thyroid and adrenal function in the ring dove (Streptopelia risoria) during food deprivation and a breeding cycle.

The concentration of plasma triiodothyronine (T3), thyroxine (T4), corticosterone, and glucose as well as body weight and food intake were measured in pairs of ring doves throughout a breeding cycle and during food deprivation. During courtship and incubation the levels of plasma T4 were significantly higher in males than in females. A transitory decrease in food intake in both sexes was measured at the onset of incubation but was not associated with a change in body weight or in levels of plasma thyroid hormones. After the eggs had hatched, food intake increased but was associated with a reduction in body weight and concentrations of plasma T3 and T4, although plasma corticosterone and glucose both increased. Food deprivation for 48 hr resulted in a significant fall in the concentration of plasma T3 and an increase in plasma corticosterone. These changes suggest that all the food was not being digested by the adult birds during brooding but was almost exclusively regurgitated to feed the squabs.

Adrenal Glands↗

PubMed1991

Effect of dietary boron supplementation on egg production, shell quality, and calcium metabolism in aged broiler breeder hens.

Three experiments were conducted using aged broiler breeder hens (greater than 60 wk) to investigate the effects of supplemental B on egg production (EP), shell quality, and Ca metabolism. Experiment 1 had a 2 x 2 factorial arrangement of treatments: 1) high Ca (3.5%); 2) high Ca plus B; 3) low Ca (1.5%); and 4) low Ca plus B; using 32 60-wk-old hens. The B levels were basal and 100 ppm supplemental for the first 2 wk of the experiment and reduced to 60 ppm for the remaining 3 wk. Egg production, shell thickness (ST), and egg specific gravity (SG) were recorded weekly. In Experiment 2, 40 60-wk-old hens were divided into two groups: high and low shell quality. Each group was further divided into two subgroups and fed a low-Ca basal diet with or without supplemental B. The level of B supplementation and the experimental period was the same as in Experiment 1. In Experiment 3, 52 75-wk-old hens were force-molted. After molting, 36 hens were fed a commercial layer diet with the remaining 16 hens fed the control diet supplemented with 100 ppm B. Blood samples were taken during the nonlaying and laying periods, respectively. The results showed that B significantly (P less than .05) depressed EP in Experiment 1 but not in Experiments 2 and 3. Supplemental B decreased plasma Ca when hens were fed a diet containing high Ca levels (3.5%). Supplemental B did not affect SG, ST, or Ca retention, but did significantly increase tibial bone ash percentage (P less than .05).(ABSTRACT TRUNCATED AT 250 WORDS)

Aging↗